Pharos Manual[1].pdf

User’s manual

Updated: March 7, 2011

Printed: January 3, 2012

© Light Conversion Ltd.

P/O Box 1485, Saulėtekio al. 10

LT-10223 Vilnius, Lithuania

Email: [email protected]

Web: http://www.lightcon.com

Support: [email protected]

mailto:[email protected]

http://www.lightcon.com/

mailto:[email protected]

2

1 PREFACE

This manual contains user information for safe installation and operation of PHAROS laser

system.

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Read this manual carefully before operating laser for the first time. Special attention must be

given to material in chapter “LASER SAFETY” that describes safety hazards and precautions

against them.

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Use of controls, adjustments or procedures other than those specified in this manual may

result in exposure to hazardous radiation and/or damage of equipment.

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Thank you for using Light Conversion products.

Support needs

If you have any technical questions or problems please contact our authorized representative

or Light Conversion directly:

Light Conversion Ltd.

Keramiku 2b,

LT-10233 Vilnius, Lithuania

Email: [email protected]

Web: http://www.lightcon.com

3

1.1 Electrical and Environmental Specifications

Electric* 110VAC, 50-60Hz, 20A

220VAC, 50-60Hz, 10A

*Chillers used with PHAROS require appropriate commutation of the mains transformer

located inside the chiller.

* Some models of High Voltage supplies used with PHAROS laser system are designed for

single mains voltage (110VAC or 220VAC).

For Indoor use only

Altitude Up to 2000 m

Operating temperature 15-30°C (air conditioning recommended)

Relative humidity 20-80% (non- condensing)

4

Table of Contents

User’s manual ............................................................................................................................. 1

1 PREFACE ........................................................................................................................... 2

1.1 Electrical and Environmental Specifications ............................................................... 3

2 LASER SAFETY ............................................................................................................... 6

2.1 Optical safety. .............................................................................................................. 6

2.2 Electrical safety ............................................................................................................ 7

3 SYSTEM DESCRIPTION AND SPECIFICATIONS ..................................................... 11

3.1 PHAROS configuration ............................................................................................. 11

3.2 Oscillator .................................................................................................................... 14

3.3 Stretcher/compressor ................................................................................................. 14

3.4 Regenerative amplifier ............................................................................................... 14

3.5 Mechanical design ..................................................................................................... 18

3.5.1 Regenerative amplifier ....................................................................................... 20

3.5.2 Oscillator ............................................................................................................ 25

3.5.3 Stretcher/compressor .......................................................................................... 30

3.5.4 Pockels cell driver and High voltage supply ...................................................... 32

3.6 Specifications ............................................................................................................. 34

4 Operation and maintenance of the system ........................................................................ 35

4.1 Installation ................................................................................................................. 35

4.2 Quick start .................................................................................................................. 40

4.3 Switching-off ............................................................................................................. 41

4.4 Setting parameters ...................................................................................................... 42

4.4.1 Setting pump current regenerative amplifier ...................................................... 42

4.4.2 Setting cavity dumping time ............................................................................... 42

4.4.3 Setting pump current of oscillator ...................................................................... 43

4.4.4 Running RA at low repetition rates .................................................................... 43

4.4.5 “RA level” protection ......................................................................................... 44

4.5 Maintenance ............................................................................................................... 45

5 Control Software .............................................................................................................. 46

5.1 Installing PHAROS application and driver ............................................................... 46

5.2 Architecture of PHAROS application ........................................................................ 47

5.3 PHAROS application control windows ..................................................................... 49

5

5.3.1 “Connection” window ........................................................................................ 49

5.3.2 “Power Supply Controller” window ................................................................... 49

5.3.3 “Environment” window ...................................................................................... 50

5.3.4 “Osc./RA Bar Driver” window ........................................................................... 51

5.3.5 “Oscillator” window ........................................................................................... 51

5.3.6 “RA” window ..................................................................................................... 52

5.4 Protection of laser configuration parameters ............................................................. 53

6 Remote Control Module ................................................................................................... 55

6.1 Oscillator control ....................................................................................................... 55

6.2 RA control .................................................................................................................. 57

6.3 LDD control ............................................................................................................... 58

7 Cables and connections .................................................................................................... 59

7.1 Interlocks and “RA state” indication ......................................................................... 61

8 Timing Electronics Module (TEM) .................................................................................. 63

8.1 Principle of operation ................................................................................................. 66

8.2 Timing of laser control signals .................................................................................. 67

8.3 Pulse Picker operation modes .................................................................................... 69

8.4 External laser control interface .................................................................................. 70

8.5 Controlling TEM parameters ..................................................................................... 75

8.6 TEM failures/ warnings flags .................................................................................... 78

6

2 LASER SAFETY

PHAROS is CLASS IV laser product that poses safety hazards if not used properly. Laser

produces output beams that may cause devastating and permanent eye damage, may have

sufficient energy to ignite materials, and may cause significant skin damage.

2.1 Optical safety.

PHAROS emits infrared femtosecond pulses with average power of several watts. Each of the

pump laser diode modules emits optical power of up to 60 W. Direct viewing of laser output

beam or even specular reflection from polished surfaces can cause instantaneous and

permanent eye damage and/or possible blindness.

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Avoid viewing the beam and specular reflections. Wear protective eyewear at all times when

aligning and operating PHAROS. Make sure that your protective glasses cover all the

wavelengths emitted by laser!

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PHAROS beams are powerful enough to burn skin, clothing or paint. Laser beam can ignite

substances in its path even at some distance. It also can damage light sensitive elements such

as video cameras, photodiodes, etc.

For this reasons, and other, user is advised to follow the precautions below:

- Never look directly into the light source or to scattered laser light from any reflective

surface.

- Wear protective eyewear at all times; choose protective eyewear depending on

wavelength and intensity of the radiation, conditions of use, and visual function

required.

- Maintain experimental set-ups below eye level.

- Set up energy absorbing targets and shields preventing unnecessary reflections or

scattering.

- Maintain a high ambient light level in laser operational area. This keeps the eye’s

pupils constricted, thus reducing the possibility of eye damage.

- Avoid blocking the output beam or its reflection with any part of your body. The

intensity of beam can easily cause skin burns or ignite clothing.

- Extreme caution must be exercised when using volatile solvents in the vicinity of laser.

7

- Limit laser access only to qualified users who are familiar with laser safety practices

and aware of dangers involved.

- Use the laser in a closed room. Laser light remains collimated over long distances and

therefore presents potential hazard if not confined.

- Post warning signs near the laser operation area.

2.2 Electrical safety Hazardous voltages are present in the PHAROS laser head and power supply units.

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- Never remove the access covers of power supply and laser electro-optical units unless

power supply is switched off and disconnected from the mains. Voltages present on

these components present safety hazard, which could result in personal injury or death.

- Do not connect or disconnect any cables with power supply turned on.

- Any grounding interruption outside or within PHAROS system will pose an electrical

shock hazard and could make the apparatus inoperative.

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Description of all PHAROS labels is presented in a table and figures below.

Table 2-1 Description of PHAROS labels

No. Label Description

1.

Manufacturer identification label is

located on the end panel of the laser.

2.

Product identification label is located

on the end panel of the laser.

8

3.

Warning logotype is located on the end

panel of the laser. Depending on the

device model actual radiation pulse

energy and duration are recorded on

label.

4.

Aperture label is located above the

system aperture on a front panel of the

laser. Depending on the device model

actual radiation pulse energy and

duration are recorded on label.

5.

Aperture label is located below the

system aperture on a front panel of the

laser.

6.

Product certification label is located on

the end panel of the laser.

7.

Ground contact label is located on the

end panel of the laser.

8.

Warning label is located on the top

cover of the power supply.

9.

Product identification label is located

on the end panel of the power supply.

9

Fig. 2-2 Location of labels on the end panel of PHAROS laser head. Label description is

given in Table 2-1

Fig. 2-1 Location of labels on front panel of PHAROS laser head. Label description is

given in Table 2-1.

6

1

2 7

3

4

5

10

Fig. 2-3 Location of labels on the end panel of PHAROS power supply. Label description

is given in Table 2-1.

8

9

11

3 SYSTEM DESCRIPTION AND SPECIFICATIONS

3.1 PHAROS configuration PHAROS is a high repetition rate femtosecond laser system based on chirped pulse

amplification (CPA) technique, which uses directly diode-pumped Yb:KGW (ytterbium doped

potassium gadolinium tungstate) as active medium. Description of a typical CPA system can

be found in books covering topics on femtosecond lasers (e.g., W.Koechner, Solid State Laser

Engineering, Springer-Verlag, NY; J.C. Diels and W. Rudolph, Ultrashort laser pulse

phenomena, Academic Press, NY; or on the internet http://www.rp-

photonics.com/chirped_pulse_amplification.html). The PHAROS laser head comprises of Kerr

lens mode-locked Oscillator (OSC), Regenerative Amplifier (RA) and Stretcher-Compressor

(S-C) units (see Fig. 3-1). The full system also incorporates an optional Remote Control

Module (Fig. 3-1 (b)), power supply for laser diodes (Fig. 3-2) and appropriate water chiller

that removes excess heat from the operating system, as well as stabilizes laser body

temperature.

PHAROS operation is automatically controlled by driving electronics and operating

parameters can be adjusted from Remote Control Module or external PC that is linked via

USB interface. Dedicated PC software and well developed library of commands are also

included.

As an option, PHAROS system can also include an electo-optical Pulse Picker for output pulse

control and contrast enhancement and/or motorised delay line for automated Compresor

lenght ajustment.

http://www.rp-photonics.com/chirped_pulse_amplification.html

http://www.rp-photonics.com/chirped_pulse_amplification.html

12

(a)

(b)

Fig. 3-1 PHAROS laser head: (a) OEM version, (b) with external enclosure.

13

Fig. 3-2 PHAROS power supply unit.

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3.2 Oscillator The oscillator (OSC) employs a cavity with chirped mirrors and a prism pair that is used for

fine adjustment of group velocity dispersion. Yb:KGW crystal is end pumped by high

brightness laser diode module. Generation of femtosecond pulses is ensured by Kerr lens

modelocking, which is induced by perturbing the cavity length. Once started, the modelocking

usually sustains throughout the days and is immune to minor mechanical impact. Repetition

rate of oscillator pulses is 76 MHz, while typical output power is in the range of 600-

1200 mW. Spectral bandwidth is within 16-20 nm (FWHM) and yields corresponding pulse

duration of ~70-90 fs. The OSC output power can be actively stabilized by power lock

function. An electronic feed-back loop ensures compensation of the output power drift by

changing the pump diode current.

3.3 Stretcher/compressor Stretcher and compressor of the PHAROS system employ transmission diffraction grating and

both are enclosed in the same housing. By changing the compressor length it is possible to

tune the output pulse duration from a minimal value, which is laser model dependent, to a

maximum one of about 10 ps (limited by the length of translation stage used in compressor).

Compressor length adjustment in the standard PHAROS system is manual; whilst a computer

controlled motorized stage can be installed as an option.

3.4 Regenerative amplifier Regenerative amplifier incorporates a Yb:KGW crystal that is pumped by one or two

continuous wave (CW) pump modules. A single BBO (beta-BaB2O4) Pockels cell within the

amplifier cavity is used to inject the seed and dump the amplified pulse. Any pump light

modulations or fast changes in the repetition rate are not allowed within the CW pumped

regenerative amplifiers. These fast perturbations may cause optical damage of the cavity

components due to uncontrolled increase in pulse energy.

An optional external pulse picker (PP), which is based on the second Pockels cell, can be used

to control every pulse from the RA output. The pulse picker is installed in the same housing of

regenerative amplifier within the beam path to the compressor module. The high voltage (HV)

switches together with HV supplies for both Pockels cells are located outside of the housing as

separate modules. In high repetition rate (500 kHz) PHAROS systems a more powerful HV

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supply comes as a separate unit (19” standard) in the same rack as power supply of laser diode

bars.

CW pumped regenerative amplifiers have a specific non-saturated form of pulse train in the

RA cavity (Fig. 3-3). The form of the train is determined by CW pump and relatively low gain

of amplifier at repetition rates higher than inverse life-time of upper level of a gain medium

(0.35 ms for Yb:KGW crystal). A steady-state condition for inversion and pulse energy

requires relatively early cavity dumping in order to sustain sufficiently high gain for the

following (next) pulse. CW pumped amplifiers have three typical regimes of operation which

are listed in Table 3-1.

CW pumped regenerative amplifier is a highly non-linear system, which can lead to output

pulse energy bistability at repetition rates from 5 kHz to 40 kHz. The bistabily can be detected

by monitoring the output photodiode signal with an oscilloscope. It manifests as two

alternating in time output pulse energies. This phenomenon can be eliminated by reducing the

cavity dumping time.

16

Regimes of RA operation

Table 3-1

Repetition

rate

Pulse energy Peculiarities of RA operation Warnings

<5 kHz 0.4-1.0 mJ - High gain

- Increased risk of optical

damage due to high pulse

energy

- Possible self-phase

modulation

Do not exceed maximum

pulse energy (too high

pump current, too long

cavity delay time)

5-40 kHz 100-400 J - Moderate gain

- Bistability at long cavity

damping times

Check for bistabilty.

Reduce delay time or

pump current to avoid

bistability.

>40 kHz < 100 J - Low gain

- Low pulse energy

- high output power

Too high output power can

lead to thermal lensing and

degradation of beam

quality.

17

Fig. 3-3 Typical pulse train in the cavity of CW pumped regenerative amplifier.

Note: NO SATURATION of the train is observed!

CAUTION!

DO NOT TRY TO SATURATE THE PULSE TRAIN IN THE RA CAVITY BY INCREASING

CAVITY DELAY TIME. THIS MAY LEAD TO SELF-PHASE MODULATION OF LASER

PULSE AND OPTICAL DAMAGE OF CAVITY COMPONENTS.

CAUTION!

BISTABILITY OF THE OUTPUT PULSE CAN BE OBSERVED ON THE TRAIN OF A PULSE

IN THE CAVITY. IT APPEARS AS TWO TRAINS WITH DIFFERENT AMPLITUDES.

CAUTION!

IN ORDER TO OBSERVE BISTABILTY OF OPTICAL PULSES, TRIGGERING OF AN

OSCILLOSCOPE MUST ENSURE VISUALIZATION OF TWO ADJACENT PULSES.

USE PROPER OSCILLOSCOPE WITH REQUIRED FUNCTION AVAILABLE.

18

3.5 Mechanical design Laser head of PHAROS system has a multi-module structure (Fig. 3-4 ) that includes:

- Oscillator (OSC),

- Regenerative Amplifier (RA),

- Stretcher/Compressor (S-C),

- Timing Electronics Module (TEM),

- High voltage supply for RA Pockels cell,

- High voltage supply for PP Pockels cell (optional),

- RA Pockels cell driver,

- PP Pockels cell driver (optional).

Bodies of oscillator, regenerative amplifier, stretcher/compressor and Pockels cell driver

modules are water cooled, which leads to a good heat management in the system and ensures

mechanical stability that is independent on environmental conditions. The most sensitive

modules are fixed together using three point kinematic mounts, which reduces mechanical

stress caused by thermal expansion and ensures robustness of the system.

19

Fig. 3-4 Mechanical design of PHAROS laser head.

1 - Oscillator

2 - Regenerative Amplifier

3 - Stretcher/Compressor

4 - Timing Electronics Module

5 - High Voltage supply for RA Pockels cell

6 - High Voltage supply for PP Pockels cell (optional)

7 - RA Pockels cell driver

8 - PP Pockels cell driver (optional)

4

3

1

5

6

7

8

2

20

3.5.1 Regenerative amplifier

Monolithic block of regenerative amplifier (RA) body is the main support for other units of

the laser head. It has two sections from two different sides: 1) section of the pump modules is

situated from the side of oscillator and 2) section of the RA cavity is situated from the side of

high voltage supplies. Stretcher/compressor of the system is attached to the front end of the

RA body. Oscillator of the system is attached to the RA by a three point kinematic mount.

3.5.1.1 Fixing to an optical table

PHAROS system is fixed to an optical table using three point kinematic mount with three

cylindrical bearings, which eliminate mechanical deformations caused by difference in

thermal expansion coefficients between optical table (typically made of steel) and aluminium

body of the laser head. Six M6 screws are used to fix laser head to an optical table (see Fig.

3-5). OEM laser heads have three guiding points for parallel keys (6x6x20mm) on the legs

that ensure precise positioning of laser head on to the base plate. This allows maintaining

precise direction of laser beam after removal of the laser head.

CAUTION!

NOTE, THAT IF PARALLEL KEYS ARE USED BETWEEN LEGS AND BASE PLATES,

THERE IS AN INCREASED RISK FOR MECHANICAL SHOCK DURING THE PLACEMENT

OF LASER HEAD. BE CAREFUL WHILE LOCATING THE LASER HEAD IN TO CORRECT

POSITION.

21

Fig. 3-5 Bottom view of PHAROS laser head (OEM vesion). Fixing points are marked with

arrows. Red arrows – M6 screws, brawn arrows – 6x6x20mm parallel keys.

Fig. 3-6 Bottom view of the PHAROS laser head (with external enclosure). Six fixing holes are

marked with red arrows.

22

3.5.1.2 Connections

All the connections to regenerative amplifier are presented in

Fig. 3-7.

Fig. 3-7 Connections to regenerative amplifier:

1 – Pump current of LD bars.

2 – Water from chiller (inlet to laser head), labeled.

3 – Water to chiller (outlet of laser head).

4 – Water from Pockels cell driver.

5 – Water to oscillator.

6 – Water from oscillator.

7 – Water to Stretcher/Compressor.

8 – Dry air/nitrogen to section of pump modules.

9 – Dry air/nitrogen to section of laser cavity.

10 – CAN bus connector under the cover.

2 1

4

7

6

10

5

3 8

9

23

3.5.1.3 Adjustment screws

Micrometer screws for regenerative amplifier mirror adjustment are situated on the rear side

of RA (see Fig. 3-8).

WARNING !

DO NOT ADJUST MIRRORS OF THE REGENERATIVE AMPLIFIER WITHOUT

ADVICE OF AN AUTHORIZED REPRESENTATIVE. THIS MAY CAUSE COMPLETE

MISALIGNMENT OF THE SYSTEM. CONSULT MANUFACTURER OR

AUTHORIZED REPRESENTATIVE BEFORE ADJUSTING ANY MIRRORS.

Fig. 3-8 Micrometer screws for mirror adjustment of regenerative amplifier.

1 – Cavity mirror No.1, horizontal direction.

2 – Cavity mirror No.1, vert dir.

3 – Cavity mirror No.2, vert dir.

4 – Cavity mirror No.2, hor dir.

5 – Output folding mirror, vert dir.

6 – Output folding mirror, hor dir.

7 – Inspection window.

8 – Adjustment of seed direction to RA

8

7

1

3

2

4

5 6

24

3.5.1.4 Photodiodes

Four photodiodes are used to monitor the performance of regenerative amplifier:

1. Internal power meter. Slow photodiode (bandwidth < 1 kHz) is used to monitor the

output power. The photodiode is located in the RA section of pump modules. The

signal of internal power meter is used by a controller of the system. The internal power

meter cannot be calibrated for absolute output power measurements. It is used for

relative measurements and output power stabilization.

2. RA level. Fast photodiode for monitoring pulse amplitude in the RA cavity. Signal of

this photodiode is used by Timing Electronics Module (TEM) to limit the maximum

pulse energy inside RA cavity, and thus protecting optical components from damage.

The photodiode is located between the body of RA and Stretcher/Compressor.

3. RA train. Fast photodiode for monitoring pulse train in the RA cavity. The signal of

this photodiode is delivered through the Timing Electronics Module to the output

panel of TEM. The photodiode is located behind end mirror of the cavity of RA under

the cover on top of RA (Fig. 3-9).

4. Output pulse. The photodiode is located within the housing of stretcher/compressor

module. Signal of the photodiode is delivered through the Timing Electronics Module

to the output panel.

Fig. 3-9 RA train photodiode is located under the cover (marked with black arrow).

25

3.5.2 Oscillator

Oscillator (OSC) module is milled from a single monolithic aluminium block that together

with its water cooled body ensures stable and robust operation. This OSC housing has two

separate sections: 1) cavity section that is from the side of regenerative amplifier (RA) and 2)

pump module section that is on the opposite side. Detector module, which includes

photodiode for OSC power monitoring, is attached to the front side of the oscillator.

3.5.2.1 Fixing

Oscillator is fixed to the RA body by three point kinematic mount (Fig. 3-10Error!

Reference source not found.) which includes two cylindrical bearings. The use of bearings

servers two purposes:

1) Elimination of possible deformations that may arise between RA and oscillator

housings.

2) Making the oscillator conveniently accessible (by lifting it up) for service purposes

without dismounting it from the RA body.

Fig. 3-10 Oscillator fixing points (indicated with red arrows)

CAUTION !

THEN OSCILLATOR IS FIXED ONLY ON TWO UPPER POINTS, THERE IS A RISK FOR

MECHANICAL IMPACT WITH THE THIRD (LOWER) FIXING POINT. THIS MAY CAUSE

MISALIGNMENT OF OSCILLATOR CAVITY.

26

3.5.2.2 Connections

Fig. 3-11 Connections to Oscillator.

1 – Pump current of LD bars.

2 – Water inlet to oscillator.

3 – Water outlet from oscillator.

4 – Dry air/nitrogen to pump section.

5 – Dry air/nitrogen to laser cavity section.

6 – Inspection window.

3

2

1

6

5

4

27

3.5.2.3 Adjustment screws and signal connections on front panel of

oscillator

Adjustment micro-screws of output mirror and end mirror of oscillator are situated on the front

side of oscillator (see

Fig. 3-12).

Fig. 3-12 Front side of oscillator with removed Detector module.

1- Output window of oscillator.

2- End mirror window.

3- Micrometer screw for adjustment of output mirror (horizontal direction).

4- Micrometer screw for adjustment of output mirror (vertical direction).

5- Micrometer screw for adjustment of end mirror (vertical direction).

6- Micrometer screw for adjustment of end mirror (horizontal direction)..

7- CAN bus connection.

8- DC supply for fast photodiodes of Detector Module.

9- Connector of internal power meter.

10- not connected

5

3

1

2

4

6

7

10

11

8

9

28

3.5.2.4 Photodiodes

Four photodiodes are used to measure signals of oscillator, they are listed in Table 3-2. Three

of the diodes are situated in the Detector module which is attached to front side of the

oscillator (Fig. 3-13). The fourth photodiode “Narrow bandwidth” is located in the

stretcher/compressor housing and monitors the spectral bandwidth of oscillator.

Signal of one fast photodiode is used to monitor pulse train in the cavity of oscillator. signal

of this photodiode is coupled directly into an output panel of the Timing Electronics Module

(PD OSC).

Signal of the second fast photodiode is used for triggering of Timing Electronics Module as a

clock for whole system. Both fast photodiodes detect leakage of an optical pulse through the end

mirror of the oscillator (arrow No.2 on

Fig. 3-12).

The third slow photodiode monitors output power of the oscillator. signal of this photodiode is

used by an internal controller.

The Narrow Bandwidth photodiode is installed in the stretcher where the spectrum of

oscillator is spread spatially. Signal of this photodiode is used to recognize whether oscillator

is mode-locked. Controller of the system generates a failure message if the signal of “Narrow

bandwidth” photodiode is too low. The signal of this photodiode is used to find optimal pump

current for the oscillator. A presence of CW component in the output of oscillator is detected

using the signal of this photodiode.

Photodiodes of oscillator Table 3-2

Photodiode Location Bandwidth

1. For Pulse Train Detector Module 300 MHz

2. Clock for TEM Detector Module 300MHz

3. Internal power meter Detector Module <1kHz

4. Narrow bandwidth Stretcher/compressor 1MHz

29

Fig. 3-13 Front side of the oscillator with the Detector module. Osc. sync connected to TEM, Osc.

PD connected to external panel.

Osc sync

Osc PD

30

3.5.3 Stretcher/compressor

Stretcher of the PHAROS system is designed to produce a temporal pulse stretching using

positive dispersion diffraction grating setup. Output of the stretcher is seeded into regenerative

amplifier for amplification and subsequent compression. Compressor of the Pharos system is

built into the same housing as the stretcher and shares the same diffraction grating. By

changing the compressor length it is possible to induce negative or positive pulse chirp and

consequently change the output pulse duration. PHAROS with motorized translation stage this

can be done from the PHAROS software, while in PHAROS with manual compressor length

adjustment a micrometer screw is located under the cover 1 (see Fig. 3-14). In order to adjust

the compressor length it is necessary to remove the cover (1 in Fig. 3-14) and turn the

micrometer screw using hex key. Clockwise rotation produces a positive chirp whilst

counterclockwise yields a negative one.

CAUTION!

ADJUSTMENT OF COMPRESSOR’S THIRD ORDER DISPERSION (OPENING 3,

FIG. 3-15) REQUIRES SPECIAL SKILLS. CONTACT MANUFACTURER OR YOUR

AUTHORIZED REPRESENTATIVE FOR INSTRUCTIONS.

31

Fig. 3-14 Stretcher/compressor of PHAROS system. Rear view.

1- Opening for manual adjustment of the length of the compressor (adjustment of pulse

duration, Second Order Dispersion). Remove the cover for adjustment.

2- Water connection for temperature stabilization.

3- Signal connections:

NB – Narrow Bandwidth. Monitors bandwidth of the oscillator spectrum .

LVL – RA level. Monitors pulse energy in the cavity of RA.

PD – Output Photodiode. Monitors output pulse energy.

Fig. 3-15 Stretcher/compressor of PHAROS system. Front view.

1- Output window.

2- Micrometer screw of folding output mirror.

3- Opening for adjustment of Third Order Dispersion (TOD).

4- Shutter of the seed light. O - opened, C – closed.

1

2

3

1 2 3

4

32

3.5.4 Pockels cell driver and High voltage supply

For removal of HV supply or Pockels cell drivers from the RA do following:

1. Release 4 screws from the top of HV supply modules (see 1 in Error! Not a valid

ookmark self-reference.).

2. Pull and rotate by 90deg a plastic chuck (see 2 in Error! Not a valid bookmark

elf-reference.).

3. Detach driver and HV supply.

4. Disconnect water tubes and cable connections.

Back side of the Pockels cell drivers and HV supplies with all the connections are shown in

Fig. 3-17.

CAUTION!

THERE ARE SPECIAL SHIELDING METAL RINGS BETWEEN THE DRIVER AND RA.

DO NOT FORGET TO PUT THEM DURING ASSEMBLING.

WARNING!

DO NOT TRANSPOSE TIMING CABLES NEITHER ON POCKELS CELL DRIVER SIDE

NOR TIMING ELECTRONICS MODULE SIDE. THE TRANSPOSE OF TIMING CABLES

CAN LEAD TO UNCONTROLLED AMPLIFICATION OF AN OPTICAL PULSE IN THE

CAVITY OF RA AND AS A CONSEQUENCE IRREVERSIBLE OPTICAL DAMAGE OF

OPTICAL COMPONENTS OF THE LASER CAVITY.

WARNING!

DO NOT START THE LASER IF TIMING CABLES ARE NOT CONNECTED. THIS CAN

LEAD TO IRREVERSIBLE OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE

LASER CAVITY.

WARNING!

DO NOT START THE LASER IF POCKELS CELL DRIVERS ARE GROUNDED. THIS CAN

LEAD TO IRREVERSIBLE OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE

LASER CAVITY.

33

Fig. 3-16. Removal of Pockels cell drivers and High voltage supplies.

Fig. 3-17 Connection of Pockels cell drivers and HV supplies to RA. View from the side of RA.

1- HV connectors to Pockels cells.

2- Timing connectors ON/OFF.

3- Water connection.

4- CAN bus to HV supply.

2 2 1

4

3

2 1

34

3.6 Specifications Due to continuous product improvement program, specifications may change without notice.

Parameter PHAROS-4W PHAROS-6W PHAROS-SP

Central wavelength, nm 1030±3 1030±3 1030±3

Average output power, W 4 61

5

Repetition rate, kHz 1-2002 1-200

2 1-200

2

Typical pulse duration*, fs 280 280 180

Maximum pulse energy, mJ 0.2 0.2 1.0

Stability of pulse energy, STD <0.5% <0.5% <0.5%

Oscillator pulse duration, fs <90 <90 <90

Oscillator output power, W >0.63 >0.6

3 >0.6

3

Oscillator repetition rate, MHz 764

764

764

Weight of OEM laser head 34kg

Weight of laser head with

external enclosure

42kg

Weight of power supply 13kg

Weight of chiller (approx.) 32kg or 40kg

* defined at FWHM and slightly varies with repetition rate

1 Extendable up to 10 W

2 Versions with higher repetition rates (up to 1 MHz) are available.

3 High power oscillator (>2 W) can be integrated then partial oscillator output is necessary.

4 Customized repetition rates and/or active stabilization of the cavity length are available on request.

Optional accessories

- Pulse picker for “pulse-on-demand” operation.

- Stepper motor equipped translator for computer controlled adjustment of compressor

length (maximum pulse duration ca. 10 ps).

-

35

4 Operation and maintenance of the system

4.1 Installation

CAUTION!

YOUR PHAROS LASER WAS PACKED WITH GREAT CARE, AND IT’S

CONTAINER WAS INSPECTED PRIOR TO SHIPMENT. IF ANY MAJOR DAMAGE

WAS NOTICED AT THE TIME OF RECEIPT (HOLES IN THE CONTAINER, WATER

LEAK, CRUSHING, ETC.) PLEASE NOTIFY THE CARRIER AND MANUFACTURER.

CAUTION!

IF LASER WAS TRANSPORTED IN COLD WEATHER CONDITIONS, KEEP IT IN

TRANSPORTATION BOXES FOR AT LEAST 6 HOURS AT ROOM TEMPERATURE

IN ORDER TO PREVENT POSSIBLE WATER CONDENSATION ON THE SENSITIVE

COMPONENTS OF THE LASER AFTER AN OPENING. LASER HEAD IS

HERMETICALLY SEALED IN PLASTIC BOX.

CAUTION!

IT IS RECOMMENDED THAT YOU WAIT FOR YOUR LIGHT CONVERSION

REPRESENTATIVE TO UNPACK YOUR SYSTEM. IN NO EVENT SHOULD YOU

ATTEMPT TO INSTALL THE LASER YOURSELF WITHOUT PRIOR AGREEMENT

OF LIGHT CONVERSION LTD. ANY UNAUTHORIZED ACTION WILL VOID YOUR

WARRANTY AND YOU WILL BE CHARGED FOR THE REPAIR OF ANY RESULTED

DAMAGE.

1. Carefully remove laser head, power supply and chiller from the transportation boxes.

Retain these boxes for possible transportation in the future.

2. Remove humidity absorbers from the laser and power supply.

3. Remove a tin shell and metal sheet from the bottom of laser head (for OEM laser

heads only).

4. Place laser head on the optical table and fix it using appropriate screws. Fixing of the

OEM laser head is shown in Fig. 3-5, while fixing of the laser head with external

enclosure is shown in Fig. 3-6. Note that you’ll need to remove the cover of PHAROS

external enclosure, consult Fig. 4-1.

WARNING!

AVOID HARSH MECHANICAL IMPACTS WHEN PLACING LASER HEAD ON THE

OPTICAL TABLE. THIS CAN CAUSE MISALIGNMENT OF THE LASER CAVITY.

36

Fig. 4-1. Cover removal in the case of laser with external enclosure.

Fig. 4-2. Water inlet and outlet of the PHAROS laser head.

1. Bend the fixer

3. Raise up

2. Thrust forward

WATER

OUTLET

WATER

INLET

37

5. Connect laser diode power cable (4 high current cables) from power supply to laser

head.

6. Connect control cables from Power supply to Remote Control Module and from Power

supply to laser head.

7. If you intend to control laser operation from a personal computer, connect computer

and power supply via USB cable and install the PHAROS software.

WARNING!

PHAROS LASER MUST BE GROUNDED BEFORE CONNECTING USB CABLE.

IMPROPER GROUNDING CAN DAMAGE COMPUTER AND/OR PHAROS POWER

SUPPLY.

8. Connect water tubes from chiller to laser head. Water inlet to laser head is marked

with red label (see Fig. 4-2).

CAUTION!

THE DIRECTION OF COOLING WATER FLOW IS IMPORTANT FOR PROPER

SYSTEM OPERATION. CONNECT THE HOSES DILIGENTLY WITH PROPER

FLOW DIRECTION. INCORRECT FLOW MAY CAUSE UNSTABLE OPERATION

AND POSSIBLE DAMAGE.

CAUTION!

CHILLER SHOULD BE LOCATED SO THAT THE WARM AIR EXHAUST AT THE

BACK PANEL WOULD NOT BLOW INTO THE POWER SUPPLY UNIT AND VICE

VERSA.

9. Fill the chiller with distilled water. Note that manufacturer do not recommend using

any special water additives to preventing corrosion and/or growth of algae. Consult the

manufacturer before using any water additive.

CAUTION!

USE ONLY STEAM-DISTILLED WATER. THE USE OF HIGHLY DE-IONIZED

WATER MAY CAUSE CORROSION DAMAGE.

10. Connect the mains cables for chiller and power supply.

11. Check connections of other cables. See Chapter 7 of this Manual.

12. Switch-on the chiller and check for water leakage. Add water if necessary. The

temperature of cooling water must be set to room temperature at the beginning. Then it

must be changed slowly (1degC in 5min.) to operating temperature 20-23 degC

defined in the Factory test certificate. Water flow from chiller should not exceed

38

3 l/min and water pressure should be <3 bars. It is advised to use the same values as in

the Factory test certificate. Read chiller manual for adjustment of flow and pressure.

CAUTION!

FAST CHANGE OF LASER HEAD TEMPERATURE MAY CAUSE MISALIGNMENT

OF THE SYSTEM.

13. Turn key to position “Laser ON” to start pump laser diodes. Check for pump currents

of the oscillator and amplifier in Factory test certificate. Change the pump currents if

necessary.

14. Warm-up the laser for 5-10min. Output power of oscillator in CW regime must reach

value stated in Factory test certificate (100-400mW).

Starting oscillator

1. Connect an oscilloscope to “PD OSC” BNC connector for observation of pulse train in

the oscillator.

2. Press “Oscillator” “Start” button on Remote Control Module (RCM) or appropriate

button on the Pharos software. This moves prism inside the cavity of oscillator to

initiate mode-locking. “Running” indication on the “Status” line of RCM must appear

(electronics detects 76MHz frequency in the signal of photodiode). If oscillator doesn’t

start, increase or decrease pump current and try to start oscillator again.

3. To optimize performance of the oscillator use a signal of the “Narrow Spectrum”.

photodiode(RCM: Osc, NB detector; Pharos software: “RA”, “Narrow Spectrum”).

First measure interval of pump currents at which signal of “Seed control” photodiode

changes from its maximum value (A1, point there CW component in optical spectrum

appears) to its minimum value (A2, laser jumps from mode-locking to CW regime). Set

the pump current such that signal of “Narrow Bandwidth” photodiode acquires its

average value ((A1-A2)/2).

4. For long term stability this value of the output power can be locked using “Power lock

function” which activates feedback loop between an internal power meter reading and

pump diode current.

FEGI

Highlight

39

Starting regenerative amplifier

Before starting RA check the following:

a) RA delay doesn’t exceed the value defined in the Factory test certificate.

b) RA repetition rate is high enough (>75kHz). Risk of optical damage of optical

components is reduced at high repetition rates and short RA delays.

c) Pump current of RA doesn’t exceed the value defined in the Factory test

certificate.

1) Connect a cable from oscilloscope (>300MHz bandwidth or 2Giga-samples/sec, time-base

100-200ns/div, 50Ω input impedance) to “Scope” BNC connector on Timing Electronics

Module for triggering of an oscilloscope. Use connection “RA” for monitoring pulse train in

the cavity.

2) Install optical power meter on the output of laser.

3) Start the amplifier by pressing “Start” and “PP closed” buttons.

The following parameters of the system must be checked after an installation:

- Mode-locked range of oscillator.

- Mode-lock staring range of oscillator.

- Output power of the system (pump current, cavity delay time and repetition rate should

be the same as indicated in Factory test certificate)

- Output power of the system in Q-switched regime with closed seed light (pump

current, cavity delay time and repetition rate should be the same as indicated in

Factory test certificate).

FEGI

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FEGI

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FEGI

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FEGI

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FEGI

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FEGI

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40

4.2 Quick start When laser is installed and properly adjusted starting procedures is described in Table 4-1.

Table 4-1

Action Position Result

1. Switch the key to position

“Laser on”

Power supply Switches on:

- chiller,

- HV supply for Pockels cells,

- pump current of oscillator

- pump current of RA

2. Wait 10min Heats up pump module, sets

proper pump wavelength

3. Press button “Start” in window

of oscillator

Remote Control

Module or software

on computer

Initiates mode-locking in the

oscillator

4. Press button “Lock” in

window of oscillator

Remote Control

Module or software

on computer

Locks the output power of the

oscillator using a signal of

internal power meter.

5. Set the required parameters of

the regenerative amplifier:

- pump current,

- cavity delay time,

- repetition rate

Remote Control

Module or software

on computer

6. Press “Start” in window of RA Remote Control

Module or software

on computer

Starts operation of RA

7 Press “PP closed” in window

of RA

Remote Control

Module or software

on computer

Activates pulse picker and

directs RA output light to the

output aperture of the laser

41

4.3 Switching-off

Switching-off procedures are listed in the Table 4-2

Table 4-2

Action Position Operation

1. Press button “Stop” Remote Control

Module or computer,

RA

Stops the regenerative

amplifier

2. Turn the key on Power supply

to position “Power off”

Power supply Slowly reduces pump currents

for oscillator and amplifier

diodes and switches-off the

system.

CAUTION!

SWITCHING-OFF OF THE LASER TAKES APPROXIMATELY ONE MINUTE, DUE

TO GRADUAL DECREASE OF PUMP CURRENT. THE MAINS ARE SWITCHED OFF

ONLY AFTER THE RA AND OSC CURRENTS WERE REDUCED TO ZERO.

42

4.4 Setting parameters

4.4.1 Setting pump current regenerative amplifier

Use Factory test certificate to determine required pump current of laser diode bars of

regenerative amplifier. The pump current may slightly vary due to the possible misalignments

in the system.

CAUTION!

IT IS ADVISED NOT TO EXCEED 50 A PUMP CURRENT. THIS MAY LEAD TO THE

REDUCTION OF PUMP BAR LIFETIME AND DETERIORATION OF OUTPUT BEAM PROFILE

DUE TO THERMAL LENSING WITHIN LASER CRYSTAL.

4.4.2 Setting cavity dumping time

Use Factory test certificate to determine required cavity dumping time of regenerative

amplifier. Output pulse duration depends on the dumping time due to a different optical path

length in the crystals (laser crystal and Pockels cell) of the cavity. Set optimal compressor

length for different dumping times. Read Chapter 4.4.4 for Running RA at low repetition

rates. See Fig. 3-3 for typical train of optical pulse in a cavity of RA.

CAUTION!

DO NOT TRY TO SATURATE THE TRAIN OF OPTICAL PULSE IN THE CAVITY OF RA

BY INCREASING CAVITY DELAY TIME. THIS MAY LEAD TO SELF MODULATION OF

AN OPTICAL PULSE AND OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE

CAVITY OF REGENERATIVE AMPLIFIER.

CAUTION!

BISTABILITY OF THE OUTPUT PULSE CAN BE OBSERVED ON THE TRAIN OF A PULSE

IN THE CAVITY. IT APPEARS AS TRAIN WITH CHANGING AMPLITUDE.

CAUTION!

TO OBSERVE BISTABILTY OF THE OPTICAL PULSE, TRIGGERING OF AN

OSCILLOSCOPE MUST ENSURE VISUALIZATION OF TWO ADJACENT PULSES.

USE PROPER OSCILLOSCOPE WITH REQUIRED FUNCTION AVAILABLE.

43

4.4.3 Setting pump current of oscillator

Use Factory test certificate to determine required pump current of oscillator. Due to the

possible misalignment of the oscillator required pump current may be slightly differ from that

one indicated in the Factory test certificate. To optimize performance of the oscillator use a

signal of the “Narrow Spectrum”. photodiode(RCM: Osc, NB detector; Pharos software:

“RA”, “Narrow Spectrum”). First measure interval of pump currents at which signal of “Seed

control” photodiode changes from its maximum value (A1, point there CW component in

optical spectrum appears) to its minimum value (A2, laser jumps from mode-locking to CW

regime). Set the pump current such that signal of “Narrow Bandwidth” photodiode acquires its

average value ((A1-A2)/2).

4.4.4 Running RA at low repetition rates

Risk of damaging of laser crystal by high energy optical pulse increases if laser is operated at

low repetition rates (<20kHz). At the low repetition rates active medium of the laser has

enough time to accumulate too much of energy in the upper level. This leads to increase in

gain and can lead to optical damage of laser crystal. This problem is also inherent for starting

the CW pumped regenerative amplifiers, therefore feature of “Soft Start” is installed in the

hardware of timing electronics. “Soft Start” feature means that at a start moment cavity

dumping time of the RA is reduced to its minimum value (<150ns) and then is increased

gradually to a set value during about 1second.

Starting laser at low repetition rates:

1. Install energy or power meter at the output of PHAROS and an oscilloscope for

monitoring the pulse train in the cavity of RA;

2. Reduce pump current of RA to 25-28A;

3. Set a proper cavity delay time from Pharos test certificate

4. Set a required repetition rate;

5. Start RA;

6. Slowly increase pump current of RA to the level of required output pulse energy. DO

NOT EXCEED MAXIMUM PULSE ENERGY ALLOWED FOR PARTICULAR

SYSTEM (1mJ, 600J or 200J pulse energies are allowed for different Pharos

44

systems). When the proper pump current is found the RA can be stopped and started at

the same pump current;

7. Check for bistability of output pulse. Bistabilty is a nonlinear phenomenon inherent for

CW pumped regenerative amplifiers as highly nonlinear systems. The bistability can

be observed on oscilloscope as appearance of two different pulse energies of adjacent

output pulses. This occurs when the pulse energy is high enough to remove a great part

of inversion accumulated in a laser crystal in a single pass so the pulse energy becomes

influenced by energy of its predecessor. For stable operation of the laser the bistability

must be eliminated by decreasing of cavity delay time in regenerative amplifier. It is

recommended to set the delay time shorter by one round trip from the “bistable” delay

time.

4.4.5 “RA level” protection

PHAROS has two level protection system against high optical pulse energy which can damage

optical components of the cavity. A dedicated photodiode is installed behind one of the

mirrors of the cavity of regenerative amplifier for monitoring pulse amplitude of the optical

pulse in the cavity. Timing Electronics Module continuously measures amplitude of the

optical pulse. Two level protection against high pulse energy is implemented in Pharos

system:

RA level WARRNING – pulse reaches dangerous energy. The system sends

warning message, but doesn’t stop the amplifier.

RA level FAIL - pulse energy is too high. The system sends warning message

and stops the amplifier.

WARNING!

THE “RA LEVEL” PROTECTION SYSTEM IS NOT FAST ENOUGH TO STOP AN

AMPLIFICATION OF A PULSE DURING A SINGLE AMPLIFICATION CYCLE. DO

NOT START REGENERATIVE AMPLIFIER AT HIGH PUMP CURRENT AND LONG

CAVITY DUMPING TIME AT LOW REPETITION RATES (SEE TABLE 3-1 FOR

DETAILS).

45

4.5 Maintenance For every day work it is important to prevent formation of algae in water of cooling system.

Appearance of algae in cooling system can lead to formation of plugs in critical places, this

cause overheating of laser crystal, softening of water tubes and possibly swamping and

damaging of the laser. To prevent formation of algae plugs it is important to change cooling

water once per three month.

The cooling system of the laser must be rinsed with clean water two times during the

replacement of the water. Water filter of the cooling system is situated on a back panel of the

chiller. Remove the filter and wash it carefully. The filter must be changed once per year.

For maintenance of the chiller read manual of the chiller.

CAUTION!

USE ONLY STEAM-DISTILLED WATER. THE USE OF HIGHLY DE-IONIZED

WATER MAY CAUSE CORROSION DAMAGE. MANUFACTURER DOES NOT

RECOMMEND USING ANY SPECIAL ADDITIVES TO WATER FOR PREVENTING

THE CORROSION AND THE GROWTH OF ALGAE. CONSULT MANUFACTURER

BEFORE USING ANY ADDITIVE TO COOLING WATER. DIFFERENT METALS ARE

USED IN THE COOLING SYSTEM AND THE WATER ADDITIVES CAN CAUSE

DAMAGE OF THE COOLING SYSTEM.

Variation of the room temperature should not exceed ±5degC for stable operation of the laser.

Recommended room temperature is 22±2deg. Each Pharos system is aligned and optimized

for defined cooling water temperature, usually 20degC or 23 degC. Operation at different

water temperature can cause a misalignment or poor performance of the system.

CAUTION!

IT IS IMPORTANT TO PREVENT WATER CONDENSATION ON THE COOLED

COMPONENTS OF THE LASER AT HIGH HUMIDITY AND TEMPERATURE IN A

ROOM. USE A PSYCHROMETRIC CHART (e.g.,

http://en.wikipedia.org/wiki/Psychrometrics) TO CALCULATE A DEW

POINT IN YOUR LABORATORY. THE DEW POINT SHOULD NOT BE HIGHER

THAN WATER TEMPERATURE FROM A CHILLER. DO NOT USE LASER IF

THERE IS A RISK OF WATER CONDENSATION. CONSULT MANUFACTURER FOR

OPTIMAL REGIME OF LASER OPERATION AT HIGH HUMIDITY CONDITIONS.

Power supply of Pharos system has air filter on the fan. The air filter must be checked in every

three months and cleaned if necessary.

http://en.wikipedia.org/wiki/Psychrometrics

46

5 Control Software

Full control of PHAROS parameters is accessible from PHAROS computer application. This

application also can be used for PHAROS state monitoring, visualization and logging.

Computer connects to PHAROS power supply over USB bus

CAUTION!

PHAROS LASER MUST BE GROUNDED BEFORE CONNECTING USB CABLE TO

PC. IMPROPER GROUNDING CAN DAMAGE COMPUTER OR PHAROS POWER

SUPPLY.

5.1 Installing PHAROS application and driver

Installation package of PHAROS application is provided on CD together with laser

documentation. The latest version of software can be downloaded from PHAROS support site

http://pharos.lightcon.com (registration required).

PHAROS application is supported on Microsoft Windows XP and Microsoft Windows Vista

32-bits operation systems. The only requirement for a PC is one free USB socket.

To install software to PC insert installation CD into CD drive or run Setup.exe file and follow

installation instructions.

After software is installed, connect PHAROS power supply to the mains (There is no need to

turn power supply off), plug USB cable to computer and PHAROS power supply. Windows

will detect a new hardware. On Windows Vista select: “Locate and install software” “I

don’t have the disc. Show me other options” “Browse my computer for driver software”.

On Windows XP select: “No, not his time” “Install from a list or specific location”

“Include this location in the search”.

Then browse to PHAROS installation directory\Driver (typically C:\Program

Files\PHAROS\Driver) and select kmdf_lc_usb.inf file to install.

If driver is installed successfully start PHAROS application. It will connect to the laser

automatically. If laser was not connected while starting application, button “Connect” must be

pressed in “Connection” window.

http://pharos.lightcon.com/

47

5.2 Architecture of PHAROS application

PHAROS application is designed as set of modeless windows. Every window contains

controls and indicators grouped by functions or PHAROS system subunits. Windows can be

showed or hidden using menu option View Window name. If PC monitor resolution is low,

user can choose to hide unnecessary windows. All windows can be docked inside main

application window or docked and tabbed inside each other to save display space and design

ergonomic control environment. To dock or tab window move mouse to the caption area,

press left mouse button and move window to required position. Graphical menu with

docking/tabbing options will appear near the mouse cursor.

Fig 5-1. PHAROS application

Additional graph windows can be added if long term monitoring of certain parameters is

required. To add graph windows press button or select menu Graphs Add New

Graph. Dialog with selection of graphs will appear and can be used to select parameters that

must be displayed in graphs.

Fig 5-2. Example of graph window

Parameters and positions of graph windows are saved when PHAROS application shuts down

and are restored on the next start of software. Toolbar on top of graph window provides

buttons for these operations:

48

Access graph properties ,

Auto scale of graph ,

Save data points to ASCII file ,

Save graph as image to file ,

Enable real-time backup graph data to file ,

Clear all collected data ,

Change time scale of graph from 1 minute to 64 hours ,

Standard normalized deviation of data displayed on graph.

“Graph Properties” window allow to customize graph colors and fonts, type and size of for

data points and lines, vertical axis range, to enable/ disable auto scaling and logarithmic

vertical scale.

Fig 5-3. Example of “Graph Properties” window

49

5.3 PHAROS application control windows This chapter briefly describes main functions of PHAROS application control windows. List

of all windows can be displayed expanding menu option View.

5.3.1 “Connection” window

A “Connection” window is used to select PHAROS device (if more than one laser is

connected to the same computer) and connect/disconnect to the laser. If only one laser is

connected to the computer, power supply is connected to the mains and USB cable is plugged

to computer and PHAROS power supply, application will connect to the laser automatically.

Also there is no need to disconnect while shutting down application.

Fig 5-4 "Connection" window

5.3.2 “Power Supply Controller” window

A “Power supply Controller” window can be used to switch on and off power supply, monitor

health of AC line, state of interlock inputs and internal 24V power supply load.

Fig 5-5 "Power Supply Controller" window

Behavior of “Turn power supply ON/OFF” button is equivalent to manual switching of power

key on PHAROS power supply. If power supply was switched on from computer and key

remains in position “Power OFF” to turn off laser move key to position “Power ON” and then

back to “Power OFF”.

50

CAUTION:

PHAROS ELECTRONICS PREVENTS IMMEDIATE LASER SHUTDOWN IF

CURRENT ON LD BARS IS NOT SWITCHED OFF. IN THIS CASE CURRENT ON

LD BARS IS DECREASED TO 0 AND ONLY THEN POWER SUPPLY AND LASER

ARE SWITCHED OFF. SHUTDOWN PROCEDURE CAN TAKE UP TO 1 MINUTE.

Button “Parameters” allows to access power supply parameters responsible for AC line health

monitoring.

5.3.3 “Environment” window

An “Environment” window is used to monitor PHAROS environmental parameters like

temperature of LD bars, humidity inside Oscillator and RA and to control chiller parameters.

(Only Termotek chiller is supported).

Fig 5-6 "Environment" window

To change chiller water temperature set point: enter a new temperature value and press “Set

New Water Temp.” button.

51

5.3.4 “Osc./RA Bar Driver” window

Two separate windows allow controlling LD bars current, monitoring actual current and

voltage values.

Fig 5-7 "Osc Bar Driver" window

To turn LD bar on: Press button “On”. Status label will change color to orange while current

is setting and then to green when current is set.

To turn off LD bar off: Press button “Off”. Status label will change color to grey while

current is decreasing.

To set a new current value: Enter a new current value to edit box and press button “Set” or

use scroll bar. (Arrow keys or mouse scroll button can be used to change current if scroll bar

is selected).

5.3.5 “Oscillator” window

“Oscillator” window displays actual oscillator output power, state of mode locking and

Power-lock. If modes locking is active in oscillator label “Modes locked” is highlighted. Label

“Setting power” indicates state of Power- Locking regime.

To activate oscillator’s starter: press button “Run Starter”. “Starter runs” flag will be

highlighted until starter stops.

To set a new Power- Lock set point value: enter new value in milliwatts and press button

“New Power Target”. Faster way to accept actual output power value as set point is to press

button “Lock Actual Power”.

To activate Power-Lock function: press button “Activate Power Setting”.

52

Fig 5-8 "Oscillator" window

5.3.6 “RA” window

“RA” and “Sync Failures” windows are important while controlling RA. “Failures” window

displays content of Timing Electronics Module failures register. Check boxes on the left side

of window allow masking some failures. RA won’t stop on failure that is masked. Boxes on

the right side displays accumulated failures. Accumulated values can be important while

determining reason of RA malfunction or stop.

Fig 5-9 "RA" and "Sync. Failures" windows

To start RA: press button “Start”.

To open Pulse Picker: press button “Open PP”.

53

To change cavity dumping time: press button “Cavity Dumping Time” and use scroll bar to

change delay value.

To set a new Power- Lock set point value: enter new value in milliwatts and press button

“Set”.

To activate Power-Lock function: press button “Lock”.

5.4 Protection of laser configuration parameters PHAROS system parameters are stored in internal flash memory of different controllers. All

parameters can be scanned and saved to computer disk using menu command Service Save

settings to file.

CAUTION!

IT IS HIGHLY RECOMMENDED TO BACKUP LASER PARAMETERS TO FILE AND

STORE IT IN SAFE PLACE.

Some laser parameters can be changed without disturbing laser functionality. Other

parameters are defined by laser design and modification of these parameters can cause serious

damage to PHAROS system.

To prevent intentional or unintentional modification of critical system parameters, access

levels are defined for every laser parameter. There are three different access levels used in

PHAROS system:

“User Access Level”. This level is turned on by default when PHAROS system is

powered on. It allows changing only basic set of parameters needed for day-to-day

laser operation.

“Technician Access Level”. When enabled this level allows to modify all important

laser parameters, that are not predefined by device design.

“Manufacturer Access Level”. When enabled, all PHAROS system parameters can be

modified without restrictions.

Access level is set for all PHAROS controllers simultaneously by sending special code

sequence on CAN bus. Access level remains unchanged until another correct sequences will

be received or until power off operation. On power on laser always starts with “User Access

Level”. All PHAROS internal controllers ignore parameter change commands if appropriate

access level is not set.

54

User can change access level from remote control module or using PHAROS application on

computer.

To change laser access level from PHAROS application press toolbar button with key or

select Service Access Level menu option. Choose radio button with access level, enter 4-

digit security code and press “Exit” button. If code is right- required access level will be set,

else access level will be reset to “User Access Level”.

Fig 5-10 Setting access level with PHAROS application.

PHAROS application monitors system access level and disables modification of parameters if

appropriate access level is not selected. Actual access level is displayed in main PHAROS

application window caption.

Fig 5-11 PHAROS access level indication

Security code for “Technician Access Level” is 5172.

55

6 Remote Control Module

Remote control module is small attachable unit with touch-sensitive LCD panel and knob. It

provides fast and convenient access to major PHAROS control functions and can be used to

perform all manual day-by-day operations. Module boots up in 10 seconds after laser is turned

on and is capable to execute all main PHAROS control operations.

Fig. 6-1. Remote control module

6.1 Oscillator control Left side of LCD panel displays Oscillator tab after remote control module has started. This

tab is main window for monitoring parameters and control of oscillator. It displays:

- Oscillator output power measured by internal oscillator power meter,

- Target power value used as set –point for Power-Locking function,

- Temperature of oscillator LD bar,

- Amplitude of Narrow Bandwidth Detector in stretcher/compressor,

- States of mode locking, Power-Lock and starter.

56

Fig. 6-2 Oscillator control window

Buttons and knob are used to access oscillator control functions:

To set a new Power-Lock target value- Press button “Target power” and rotate knob

keeping button pressed. Release button when “Target power” box will display required power

value.

To set actual power value as Power-Lock target value- Press and release “Target power”

button without rotating knob. Actual Oscillator output power value will be set as target for

Power-Lock.

To start/stop Power-Lock function- Press “Enable/Disable PowerLock” button.

To activate oscillator starter- Press “Starter” button. “Starter is running” label will be

displayed on the top- right corner of tab until starter will stop.

To changed oscillator’s LD bar current- Press “LDD” button to access LDD control

window.

To changed oscillator’s parameters- Press “Parameters” button to access “Oscillator

parameters” window.

57

6.2 RA control To access RA controls select tab “RA” on the main remote control module window.

Fig. 6-3 RA control window

Buttons and knob are used to access RA control functions:

To start RA- Press button ‘Start RA”.

To open Pulse Picker- Press button “PP Enable”.

To set a new Power-Lock target value- Press button “Target power” and rotate knob

keeping button pressed. Release button when “Target power” box will display required power

value.

To set actual power value as Power-Lock target value- Press and release “Target power”

button without rotating knob. Actual RA output power value will be set as target for Power-

Lock.

To start/stop Power-Lock function- Press “Enable/Disable PowerLock” button.

To change RA LD bar current- Press “LDD” button to access LDD control window.

To changed RA parameters- Press “Parameters” button to access “Oscillator parameters”

window.

To change cavity dumping time- Press “Sync params” button and select “Delay” button on

menu window.

58

6.3 LDD control

Control of Oscillator’s and RA LDD is performed from similar windows accessed by pressing

“LDD” button on Osc and RA tabs.

Fig. 6-4 Oscillator and RA LDD control windows

To start/stop LDD bar current- Press button “LDD ON”/”LDD OFF”.

To change LDD current: press button “Set I” and use knob to increase or decrease

current. Push button “Fine” for fine current adjustments or “Coarse” for fast current changing,

59

7 Cables and connections

PHAROS is packed with all necessary and optional cables that can be used with the system. If

user wants to use “Interlock” or “Emergency Stop” functions, plugs supplied on the rear panel

of power supply can be used to produce customized cables. Check Fig 7-1 for connections

between PHAROS sub units.

Fig 7-1 Rear panel of PS01-3 power supply

1

2

3

4

5

6 7

8 9

10 11

To laser

Remote panel can be connectedto power supply or directly to laser.CAN bus terminator mus be plugged to

power supply if remote panel is connectedto laser.

60

All connections from power supply are made on the rear panel. Table 7-1 contains description

of all sockets and used cables.

Table 7-1 Description of cables used with PS01-3

No. Name Description Cable code Notes

1 Control lines Control cable from power

supply to laser

C02.01

2 Control lines Control cable for Remote

Control Module

C02.05 Required only if Remote

Control Module is used.

Otherwise CAN bus

terminator must be

plugged in instead.

3 LDD outputs High current cable to LD

bars

C03.01

4 COM port Serial data cable from PS01-

3 to computer

C02.02 Required only if

PHAROS is controlled

using RS-232 interface

5 Chiller Serial data cable from PS01-

3 to Termotek chiller

C02.02 Required only for

Termotek chiller control.

6 Interlocks Plug for level 1 and 2

interlocks inputs and laser

status output.

INTERLOCK User must connect own

cable to access interlocks

function.

7 Safety Lock Plug for “Emergency

Shutdown” button

User must connect own

cable to use “Emergency

shutdown” function.

8

USB cable from PS01-3 to

computer

Required only if

PHAROS is control

using computer.

9 AC input PS01-03 power supply AC

input (C20 socket)

C01.01

(European)

C01.02

(USA, Japan)

C01.03 (UK)

10 AC output AC output with C13 socket Common output from

sockets 10 and 11 must

not exceed 10A.

11 AC output AC output with C13 socket Common output from

sockets 10 and 11 must

not exceed 10A

61

7.1 Interlocks and “RA state” indication Interlocks can be connected to DB9 male socket located on rear panel of PHAROS power

supply. Typical interlock application would be connection of breaker activated by opening

doors in laboratory or any protective cover on laser mounting frame. Two levels of interlock

function are implemented in PHAROS power supply.

Fig 7-2"Interlocks" connector

Table 7-2 Description of "Interlocks" pins

Interlock

level

Pins on DB9

connector

Connection

type

Reaction to

disruption

Procedure of

deactivation

Level 1 1,6 Normally

connected

Stops RA Connect pins 1 and

6 back

Level 2 3,7 Normally

connected

Stops RA and LD

drivers

Connect pins 3 and

7 back and switch

power supply off –

on.

Disrupting connection between two pins in interlock socket activates interlock function.

Interlock action is fully controlled by mains controller and can be adapted according to user

requirements. On standard model activated interlock Level 1 stops RA (if running) and Level 2

interlock stops RA and LD drivers. To deactivate Level 1 interlock it is enough to connect pins

1 and 6. To deactivate Level 2 interlock pins 3 and 7 must be connected and power supply

must be switched off and on.

CAUTION!

INTERLOCK PINS ARE GALVANICALY ISOLATED FROM OTHER PHAROS

ELECTRICAL CIRCUITS. CURRENT IN INTERLOCK CIRCUIT NEVER EXCEEDS

1 MA.

62

Fig 7-3 Interlock input circuit

Pins 4, 9, 5 on “Interlocks” socket are connected to the relay and can be used to get “RA

state”.

Table 7-3 "RA state" pin out

State of RA Pair of pins 4 and 9 Pair of pins 5 and 9

RA stopped closed opened

RA started opened closed

Fig 7-4 "RA state" output circuit

Note: Maximum relay settings are 0.5A/ 30V DC and 0.15A/ 125V AC.

63

8 Timing Electronics Module (TEM)

PHAROS RA operation is controlled by Timing Electronics Module. TEM is responsible for

these functions:

Synchronizes RA operation to Oscillator optical pulses,

Controls RA and PP optical gates (Pockels cells),

Protects RA components from optical damaging.

TEM is designed as aluminum box fitted on oscillator side plate.

Fig. 8-1. External view of TEM

Table 8-1 contains description of all TEM inputs and outputs.

64

Table 8-1. Description of TEM inputs and outputs

Name Direction Description Onboard

connector type

OUT PD Input/ Output

50 Ohm coaxial input/output for PHAROS output

photodiode. Signal from photodiode is retransmitted as

output for user control.

MMCX socket

RA LVL Input/ Output

50 Ohm coaxial input/output for RA level photodiode.

This sensor is used to protect RA from too high energy

pulses inside RA. Signal from photodiode is retransmitted

as output for user control.

MMCX socket

OSC

SYNC Input/ Output

50 Ohm coaxial input for oscillator output photodiode.

Signal from this photo diode is used to synchronize RA. MMCX socket

NB Input

50 Ohm coaxial input for photodiode used as RA seed

signal spectrum width monitor. Photodiode detects the

power of the edge of seed pulse spectrum to prevent

narrow spectrum (and as result short pulse) signal

injection into the amplifier.

MMCX socket

OUT1 Output Output to LED used for laser state indication. Tyco Micro-

Match socket

IN1 Input Input for cover switch (safety interlock) Tyco Micro-

Match socket

RA ON Output 50 Ohm 5V coaxial output to RA Pockels Cell driver. MMCX socket

RA OFF Output 50 Ohm 5V coaxial output to RA Pockels Cell driver MMCX socket

PP ON Output 50 Ohm 5V coaxial output to PP Pockels Cell driver MMCX socket

PP OFF Output 50 Ohm 5V coaxial output to PP Pockels Cell driver MMCX socket

CAN Outputs Internal CAN bus connectors for communication with

other PHAROS components. IDC10 socket

CTRL Input

24V power and CAN bus inputs from power supply Tyco AMP

TERMI-BLOCK

header

SCOPE Output

50 Ohm 2.4V coaxial user’s output. This output can be

programmatically configured to monitor different signals.

Output is source terminated and can be used on high

resistance load as 5V output.

MMCX socket

SYNC1 Output





MMCX socket

SYNC2 Output





MMCX socket

REMOTE Outputs/Inputs PHAROS external control interface connector. IDC14 socket

Outputs from TEM and some additional photodiodes are located on aluminum panel fitted on

the rear side of PHAROS head (see Fig. 8-2 Error! Reference source not found.).

65

Fig. 8-2. PHAROS user outputs panels (standard and OEM versions)

Table 8-2. Description of TEM inputs and outputs

Name Direction Description Onboard

connector

type

PD OUT Output 50 Ohm coaxial output from PHAROS output photodiode. BNC socket

PD RA Output 50 Ohm coaxial output from RA photodiode. This sensor

is used to monitor laser pulses inside RA cavity. BNC socket

PD OSC Output 50 Ohm coaxial output from oscillator output photodiode. BNC socket

SCOPE Output





BNC socket

SYNC1 Output





BNC socket

SYNC2 Output





BNC socket

REMOTE Outputs/Inputs PHAROS external control interface connector. DB15 socket

CTRL Inputs CAN bus and 24V supply inputs from power supply. Tuchel 5 pins

socket

66

8.1 Principle of operation

Fig. 8-3. Structure of TEM

TEM can be controlled over CAN bus (using commands sent from computer or other device

connected to the CAN bus) and from external laser control interface (using electrical signals).

TEM enters “RA Stopped; PP Closed” state after power-up. If oscillator is operational and

signal “OSC SYNC” meets amplitude, duration and period requirements, TEM can start laser.

After receiving “RA Start” command TEM sends RA ON signal enabling amplification of

oscillator’s pulse inside RA. After some period of time RA OFF signal is sent and light pulse

leaves RA. Time between RA ON and RA OFF is increased with every laser shot from some

initial value to the value defined by Cavity Dumping Time. This process is called “Soft start”

and typically takes ~ 5 seconds. During this time laser output energy varies. After “Soft start”

is finished, time interval between RA ON and RA OFF signals becomes equal to Cavity

Dumping Time and laser output power stabilizes. If pulse picker is installed, “PP Open”

commands changes TEM state to “RA Stopped; PP Opened” and two additional signals PP

ON and PP OFF are generated to open and to close pulse picker.

If “RA Stop” command is received, TEM finishes amplification cycle of last laser pulse and

enters “RA Stopped; PP Closed” state. Next start command can be issued only after 3

seconds! “RA Stopped; PP Closed” state is also entered if TEM detects error or failure.

67

Fig. 8-4. TEM state diagram (commands are sent by CAN)

8.2 Timing of laser control signals

Fig. 8-5 shows the timing diagram of TEM generated control signals with reference to optical

pulses of OSC and RA.

Oscillator period OSC): time interval between two laser pulses at the oscillator’s output.

Oscillator‘s train is monitored by OSC SYNC photodiode. This signal is also retransmitted for

user control (see Fig. 8-5). Typical oscillator period is 13-14 ns.

Laser Sync (SYNC): signal used to trigger amplification of oscillator’s pulse inside RA cavity

and emitting it from laser. Sync signal source can be internal or external generator. It takes ~6

OSC periods after Sync is received to synchronize to oscillator. Laser Sync period can have

values from 1000 s (corresponds to 1 kHz repetition rate) to ~1 s (1 MHz repetition rate).

After receiving Laser Sync signal and completion of synchronization to oscillator’s pulses

TEM generates 500 ns duration SCOPE pulse to user’s output.

From this moment additional delay tON is generated before RA ON signal is send to RA

Pockels cell driver (RA ON delay). RA ON delay can be adjusted between 0 and 45ns.

RA OF delay (tOFF)- this parameter is used in “Soft Start” procedure. Difference tOFF- tON is

used as intial Cavity dumping time (tCD) value. In ~5 seconds time Cavity dumping time is

increased from (tOFF- tON ) to tCD.

Cavity dumping time (tCD) is delay between RA ON and RA OFF signals. During this time

laser pulse is amplified inside closed RA cavity. Cavity dumping time can be increased from

145 ns to 500 ns increasing laser pulse energy. This value is reached after “Soft Start”

procedure.

Pulse picker offset (tPP offset) is adjustable delay between RA OFF and PP ON pulses. tPP offset

can be adjusted from -30 to 30 ns.

PP OFF delay to PP ON (tPP OFF) is adjustable delay between PP ON and PP OFF pulses.

HV driver delay (tDR)- is Pockels cell driver reaction delay to control pulses.

Timing parameters of signals are presented in the Table 8-3.

RA StoppedPP Closed

RA StartedPP Closed

RA StartedPP Opened

RA Start command

PP Open command

PP Close command

Error or failure

RA Stop command

68

Fig. 8-5. Laser timing diagram

Table 8-3. TEM timing parameters

min typ max jitter

Oscillator period τOSC 13-14 ns

SYNC period τSYNC 1-5* 1000 1 τOSC μs

SCOPE to Sync delay tS1 6 τOSC 1 τOSC ns

RA on delay tON 0 45 ns

RA off delay tOFF 145 500 0.5 (typical) ns

Cavity Dumping Time tCD 145 500 0.5 (typical) ns

HV driver delay tDR 60 ns

Pulse picker offset tPP offset -30 30 ns

PP OFF delay to PP ON tPP OFF 10 ns

SCOPE, SYNC1 and SYNC2

delay to PHAROS output tOUT

0.5 (peak to peak at

107 pulses)

ns

“Soft Start” time 5 s

Time between RA Stop and Run

commands 3 s

* Depends from laser model

Overall thermal peak to peak stability 500 ps in 5 -75 °C range.

Osc train

Lase Syncr

osc

Default user’s outputs

SCOPE

tS1

Outputs can be reconfigured by user to another signals.

RA ON

SYNC1(= RA ON)

tON

SYNC(

2= RA OFF)

RA OFF

tOFF

RA Pockels Cellvoltage

tDR tDR

RA train

PP ON

PP OFF

tPP OFF

PP Pockels Cellvoltage

tDRtDR

PHAROS output

tPP offset

SYNC

tOUT

69

Fig. 8-6. OSC SYNC photodiode output

8.3 Pulse Picker operation modes

Pulse Picker can operate in two modes: “closed window” and “shifted window”.

When “closed window” mode is selected, PP Pockels cell is always closed in “PP Closed”

state. This mode ensures maximal laser output contrast, but because of changing load on

Pockels cell driver’s high voltage power supply there is some output pulse energy instability

~1 ms after PP is opened.

If “shifted window” mode is selected, PP Pockels cell is opened and closed with every RA

output pulse, but phase of PP operation is shifted to prevent RA pulses to be emitted in “PP

Closed” state. This mode guaranties output pulse stability, but laser output contrast is lower.

Fig. 8-7. PP operation modes

There is one more PP mode called “OPEN mode”. In this mode PP is opened together with

RA start signal. This regime is only used while adjusting RA timing parameters.

See Chapter 8.5 for more details about PP mode selection.

70

8.4 External laser control interface

Three main PHAROS control operations: synchronization of laser pulses, starting/stopping of

RA and opening/closing of Pulse Picker can be performed with electric signals using external

laser control interface. External control interface must be enabled and configured using

computer and PHAROS control application or other user written software. See Chapter 8.5 for

more details about external interface configuration.

Fig. 8-8. TEM states diagram with external RA and PP control enabled

If external RA and/or PP control sources are selected, “RA Start” and/or “PP Open”

commands must be issued to allow laser control from external control interface. Fig. 8-8

presents diagram of TEM states when external RA and PP control sources are selected. “RA

Start” and “PP Open” commands are transmitted over CAN bus from PHAROS control

application or user’s software.

PHAROS external control interface is realized as DB15 connector

with three logical inputs and three outputs. Fig. 8-9 shows electrical

circuit of external control interface inputs and outputs.

Fig. 8-9. Pin out of PHAROS external control interface DB15 connector

RA Disabled

RA Enabled

PP Disabled

RA Start/Stop commands PP Open/Close commands

Error or failure

RA Stop command

PP Enabled

RA Running

RA RunningPP Opened

„RA on“ signal on DB15 connector„PP on“ signal on DB15 connector

PP Close command

1

2

3

4

5

6

7

8

9 SYNC IN

10 RA on/off

11 PP on/off

12 RA STATUS

13 SYNC OUT

14 FAIL

15

71

Fig. 8-10. Electrical schematic of external laser control interface inputs and outputs.

Descriptions and requirements for control inputs and outputs are listed in Table 8-4.

Table 8-4. Pin assignment of the REMOTE connector (DB15)

*laser sync is internal synchronization signal in the laser. It can be produced by internal clock

of the laser or external SYNC IN signal.

Pin No In/ Out Signal Description

1,2,3,4,5

,6,7

- GND

8 - N.C.

9 IN SYNC IN Input of the external clock for the laser synchronization – initiates

sync* of the laser. Input must be stable continuous frequency f=1-

200kHz (or 1 MHz depending on laser configuration). Duration of

the high level must be between 100 ns and 500ns.

10 IN RA on/off Starts (low level) and stops (high level) RA operation.

Stops RA operation starting from the first valid sync* of the laser.

Start – initiates “Soft Start” of RA (RA STATUS output can be used

to monitor when RA is leaving “Soft Start” and starts operating in a

defined regime.

11 IN PP on/off The signal controls the pulse picker (low level – opened, high level -

closed). The status is loaded with valid laser sync* transition.

12 OUT RA STATUS High level indicates that RA is operating in a defined regime (soft

start has finished and there are no fails in the system).

13 OUT SYNC OUT Output of laser sync* signal triggered by the internal laser oscillator

or SYNC IN. In a case of external clock the pulse duration is the

same as input pulse duration. If SYNC IN is < 500ns then SYNC

OUT is extended to ~500 ns. In case of internal clock SYNC OUT is

~500 ns.

14 OUT FAIL Indicates fail of the laser (OSC or RA). When Fail is high RA is

stopped. When fail returns to low RA on/off rising transition will

start RA operation.

15 - N.C.

72

The diagram of remote laser control signals and laser output pulse timing is presented in Fig.

8-11. Fig. 8-12 presents the waveforms for laser remote control signals. The table below

contains the required signals parameters.

Fig. 8-11. Timing of remote control signals and laser output

73

Fig. 8-12. Waveforms for laser remote control

74

Table 8-5. Parameters of signals for laser synchronization from external device

min typ max

Internal synchronization

SYNC OUT high tp 500 ns

PP on/off signal delay tpr1 0 130 ns

PP on/off signal hold tPP 50 70 ns

External synchronization

SYNC IN high tih 100 500 ns

SYNC IN period til+ tih 1-5* 1000 s

SYNC IN to SYNC OUT delay tio 100 ns

SYNC OUT high toh 500 tih if>500 ns

PP on/off signal delay in level control

mode

tPD1 150 ns

PP on/off signal hold starting from

SYNC IN in level control mode

tPP1 560 ns

PP on/off signal delay in edge control

mode

tPD2 50 100 ns

PP on/off signal hold in edge control

mode

tPP2 50 70 ns

*Depends from laser model

Note: Exact timing parameters can vary depending from TEM firmware version.

75

8.5 Controlling TEM parameters

Control of laser parameters can be performed by mean of PHAROS application started on

computer connected to PHAROS laser. TEM is controlled from RA window. This window is

used to start/ stop RA, open/ close PP, change cavity dumping time and access other TEM

parameters.

Fig. 8-13. Main RA and TEM control window

Pressing “TEM Parameters” button opens “TEM v.2 Parameters” window (see Fig. 8-14).

Fig. 8-14. TEM parameters window

76

“Configuration” frame is used to control PHAROS external control interface modes. These

parameters can be accessed in Technician and Manufacturer access levels.

“Enable external RA start source”- if checked, DB15 input “RA on/off” is used to

start/ stop RA. Additionally button “Enable” in RA window is used to allow DB15

operation.

“Enable external Pulse Picker control source”- if checked, DB15 input “PP on/off” is

used to open/ close PP. Additionally button “Enable PP” in RA window is used to

allow DB15 operation.

“Enable external sync source”- if checked, DB15 input “SYNC IN” is used to trigger

RA shots.

“Invert RA and PP control levels”- if checked, DB15 inputs “RA on/off” and “PP

on/off” are inverted: low level starts/enables RA/PP and high level stops/disables

RA/PP.

“Synchronous RA mode”- if checked and external RA sync source is not selected,

oscillator’s output pulses are used as RA sync source. Changing of RA frequency

means changing of oscillator’s output pulses divisor factor in this regime.

Fig. 8-15. Configuring laser sync sources

“PP mode” frame allows selecting between two PP regimes: “closed window” and “shifted”

window. Check chapter “Pulse Picker operation modes” for more details.

“RA frequency control” frame is used to control TEM internal frequency generator/

oscillator’s pulse divider.

“External RA frequency source control” displays actual “SYNC IN” input frequency and

value of “Locked external frequency”. If “SYNC IN” frequency differs from “Locked external

frequency” more than 10% RA is stopped and failure “Frequency out of locked range” is

activated.

“SCOPE SYNC source”, “SYNC1 source”, “SYNC2 source” frames control multiplexer of

user’s outputs (TTL levels).

Internal TEMgenerator

Pulses fromoscillator output

Divider

RA frequency control

Pulses fromDB15 SYNC IN

Laser sync in

Synchronous RA mode flag

Enable external sync source flag

77

Table 8-6. Signal sources for “SCOPE SYNC”, “SYNC1” and “SYNC2” outputs

Signal name Description

Int_Gen Signal from internal RA frequency generator.

OSC_SYNC TTL version of OSC_SYNC input of TEM.

RA_ON Copy of “RA ON” signal used to trigger RA Pockels cell.

RA_OFF Copy of “RA OFF” signal used to trigger RA Pockels cell.

PP_ON Copy of “PP ON” signal used to trigger PP Pockels cell.

PP_OFF Copy of “PP OFF” signal used to trigger PP Pockels cell.

SYNC2 Signal with user controllable delay locked to “RA OFF” signal.

RA_rdy Internal TEM signal.

RA_delay_rdy Internal TEM signal.

SYNC_OUT Copy of “SYNC OUT” output on DB15 connector.

RUNNING “RA STATUS” output on DB15 connector.

RA_Overrun “RA frequency overrun” failure output.

Power_OK “5V supply failure” output.

RA_Fail “RA common failure” output.

OUTPUT_PD_CMP0 Internal TEM signal.

OUTPUT_PD_CMP1 Internal TEM signal.

RA_LEVEL_CMP0 Internal TEM signal.

RA_LEVEL_CMP1 Internal TEM signal.

Narrow_Spectrum_Level_OK “Narrow bandwidth” failure output.

oclk Internal TEM signal.

osclk_b Internal TEM signal.

oclk_c Internal TEM signal.

prd_invalid Internal TEM signal.

prd_valid_gate Internal TEM signal.

Osc_period_short “Osc sync period too short” failure active signal.

Osc_period_long “Osc sync period too long” failure active signal.

oclk_bad Internal TEM signal.

oclk_active Internal TEM signal.

oclk_rdy Internal TEM signal.

DB15_SYNC_IN Copy of “SYNC IN” input on DB15 connector.

DB15_PP_IN Copy of “PP on/off” input on DB15 connector.

DB15_RA_IN Copy of “RA on/off” input on DB15 connector.

RA_OPEN Output active from “RA ON” until “RA OFF” signals.

PP_OPEN Output active from “PP ON” until “PP OFF” signals.

78

“RA adjustments and timing” frame contains one check box and three sliders. These

parameters can be accessed in Technician and Manufacturer access levels. “Pulse Picker

OPEN mode” check box allows enabling additional PP mode. If checked, PP is opened before

RA Pockels cell. This regime is used while adjusting TEM timing parameters. Sliders ”RA On

delay”, “RA Off start” and “PP Offset” change corresponding timing parameters tON, tOFF, tPP

OFF. Check Chapter 8.2 for more details.

“Oscillator Sync adjustments” frame contains two controls to adjust “Osc Sync Level”

parameter and “Osc too short/ too long” failure value. Button “Tune to Osc” locks TEM to

oscillator repetition rate (this operation must be performed if oscillator was readjusted or

changed).

“Narrow bandwidth failure” frame allows to adjust NB photodiode level when “Narrow

bandwidth failure” is activated.

“RA level too high” is used to adjust “RA level too high” failure and warning levels.

Modification of other TEM parameters can be achieved by accessing “TEM v.2 Advanced

Properties” window by mean of pressing button “Advanced”. This button is accessible only in

Manufacturer access level.

Fig. 8-16. “TEM v.2 Advanced Properties”

8.6 TEM failures/ warnings flags

TEM state is displayed as set of 12 different failure/ warnings flags.

RA common failure

General failure indicates that RA was stopped because of some failing behavior. The

reason of failure can be detected by the state of other failure flags.

RA level too high-warning Warning indicates that radiation level inside RA cavity reached defined warning level.

Active warning doesn’t stop laser.

RA level too high-failure Failure indicates that radiation level inside RA cavity reached failure level. If enabled,

this failure stops RA.

79

RA frequency overrun Failure indicates that RA cavity dumping time is too long for actual frequency. If

enabled, this failure stops RA. If disabled- some laser pulses are missed.

Frequency out of locked range Failure indicates that RA Sync signal is routed from external interface (DB15

connector) and its frequency differs from previously locked value more than 10%. If

enabled, this failure stops RA.

Osc sync failure General failure indicates that Osc. Sync signal from oscillator is missing, has too low/

too high amplitude, irregular period or oscillator is in double pulse mode. If enabled,

this failure stops RA.

Narrow bandwidth failure Failure indicates that narrow spectrum detector inside stretcher/compressor reached

critical value. If enabled, this failure stops RA.

Osc sync period too short This warning indicates additional information about Osc. Sync signal amplitude and

frequency. It doesn’t stop laser. “Osc. Sync level” and “Osc. Sync Period too long/ too

short” parameters must be adjusted to clear this warning.

Osc sync period too long

This warning indicates additional information about Osc. Sync signal amplitude and

frequency. It doesn’t stop laser. “Osc. Sync level” and “Osc. Sync Period too long/ too

short” parameters must be adjusted to clear this warning.

5V supply failure Failure indicates that there is problem with TEM electronics power supply circuits.

This failure always stops RA

RA LDD stopped Failure indicates that RA laser diodes driver was stopped before stopping RA. If


Osc LDD stopped Failure indicates that Oscillator laser diodes driver was stopped before stopping RA. If


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