FIBERTEK, INC.

Testing of the Space Winds LIDAR Laser Transmitter Prototype

Floyd Hovis, Fibertek, Inc.

Jinxue Wang, Raytheon Space and Airborne Systems

June 28, 2006

FIBERTEK, INC.

Program Overview

Develop a robust, single frequency 355 nm laser for airborne and space-based direct detection wind lidar systems

–All solid-state, diode pumped–Robust packaging–Tolerant of moderate vibration levels during operation–Space-qualifiable design

Incorporate first generation laser transmitters into ground-based and airborne field systems to demonstrate and evaluate designs

–Goddard Lidar Observatory for Winds (GLOW)–Balloon based Doppler wind lidar being developed by Michigan Aerospace and the University of New Hampshire for NOAA

Develop scaling to higher powers and pulse energies–Raytheon funded Space Winds Lidar Risk Reduction Laser Transmitter–Air Force SBIR to develop a 500 mJ, 100 Hz 1064 nm pump source

Iterate designs for improved compatibility with a space-based mission–Lighter and smaller–Radiation hardened electronics

FIBERTEK, INC. Status of Related Laser Development Programs

Customer Application Required 1 m Performance Program Status

Univ. of NH Doppler Wind Lidar 150 mJ at 50 Hz Delivery complete

NASA Langley Ozone DIAL 1000 mJ/pulse at 50 Hz Delivery complete

Raytheon Doppler Wind Lidar 1000 mJ at 50 Hz Testing in progress

Air Force Remote Imaging Lidar 500 mJ at 100 Hz Final build in progress

NASA Langley Phase II SBIR Seed & Metrology Laser 50 mW single frequency Prototype demonstrated

NASA Langley High Spectral Res. Lidar IIP 200 mJ at 200 Hz PDR complete

NASA Langley Mars exploration 40 mJ at 20 Hz Final build in progress

Navy SBIR Rangefinder/Designator 300 mJ at 25 Hz System study underway

NASA GSFC Doppler Wind Lidar IIP 100 mJ at 200 Hz System study underway

Single frequency pump head & resonator technology will support a significant number of next generation lidar applications

Single frequency laser development has a broad support base

FIBERTEK, INC.

Summary of Technical Approach

An all solid-state diode-pumped laser transmitter featuring:

Injection seeded ring laser Improves emission brightness (M2)

Diode-pumped zigzag slab amplifiers Robust and efficient design for use in space

Advanced E-O phase modulator material Allows high frequency cavity modulation for improved stability injection seeding

Alignment insensitive / boresight Stable and reliable operation over stable 1.0 m cavity and optical bench environment

Conduction cooled Eliminates circulating liquids w/in cavity

High efficiency third harmonic generation Reduces on orbit power requirements

Space-qualifiable electrical design Reduces cost and schedule risk for a future space-based mission

FIBERTEK, INC. Raytheon 1 J Risk Reduction Laser Optical Layout

Final System Optical Configuration

Both the original NASA Ozone amplifiers and the power amplifier have been shown to be capable of 100 Hz operation

Power amplifier

Expansiontelescope

Amplifier #2

Amplifier #1

LBO doubler

355 nm output

LBO tripler

Fiber port

Ring Resonator

Fiber-coupled 1 m seed laser

Optical isolator

FIBERTEK, INC. Packaged Single Frequency Laser Ring Laser Design Has Been Validated

Optical Schematic

Design Features

Near stable operation allows trading beam quality against output energy by appropriate choice of mode limiting aperture

30 mJ TEM00, M2 =1.2 at 50 Hz30 mJ TEM00, M2 =1.3 at 100 Hz50 mJ square supergaussian, M2 = 1.4 at 50 Hz

Injection seeding using an RTP phase modulator provides reduced sensitivity to high frequency vibration PZT stabilization of cavity length reduces sensitivities to thermal fluctuations Zerodur optical bench results in high alignment and boresight stability

1. Reverse wave suppressor2. Cube polarizer3. Odd bounce slab4. Steering wedge5. /2 waveplate6. Mode limiting aperture7. RTP phase modulator8. 45° Dove prism9. Non-imaging telescope10. RTP q-switch

1 2 3 4 5 6 2

2 4 9 5 8 5 7 2

5

10

Seed

Final Zerodur Optical Bench (12cm x 32cm)

FIBERTEK, INC. Testing of Raytheon Wind Lidar Laser Is In Progress

Completion of integrated laser and electronics modules for the BalloonWinds systemin 2005 validated many of the key elements of the Raytheon design in a packaged unit

Injection seeded single frequency ring oscillator

Key mechanical design features

High voltage power supply design

Diode drive electronics

Control electronics printed circuit boards and software

User interface

Thermal control through conductive cooling

Space-Winds Lidar Laser Transmitter

FIBERTEK, INC.

Control and Power Electronics

Raytheon Wind Lidar laser transmitter electrical design has same control electronics as BalloonWinds and updated power supplies for increased power operation

Interior view of the Laser Electronics Unit

DC-DC converters/diod

e drivers

Analog and digital control board stack

Seed laser

FIBERTEK, INC. Performance of Ring Resonator in Raytheon Laser Transmitter

Near field profile Beam quality data

Oscillator was aligned for square supergaussian output.Output energy was 60 mJ @ 50 Hz, M2 was 1.4

FIBERTEK, INC. Amplifier 1 and 2 Performance

50 Hz Testing of 1-sided pumped amplifiers 1 & 2

Dual single sided pumped amplifiers were used as the first stage of the Raytheon laser transmitter - Recent modeling showed slab bending in 1-sided pumped amplifiers is not as severe as originally believed - NASA Ozone amplifier is pump on bounce approach with only 1 array at each bounce point

Dual amplifiers operated with 75 W peak optical power per bar and 130 µs pump pulses generated 530 mJ/pulse with well a behaved near field spatial profile

Output beam profile

Input beam profile

FIBERTEK, INC. Amplifier 1 and 2 Beam Quality

Beam quality after amplifiers 1 and 2 was Mx2 = 1.9

and My2 = 1.9 for 530 mJ/pulse at 50 Hz

FIBERTEK, INC. Amplifier 3 Performance

Amplifier 3 exhibited a relatively sudden decrease in beam quality as the extracting beam was expanded to achieve higher powers. Filling the amplifier to achieve slightly over 900 mJ/pulse

is a good compromise to achieve both high pulse energies and good beam quality.

Output energies, beam sizes, near field profiles, and M2 at 50 Hz

1020 mJ/pulse, 5.3 mm x 7.5 mm

Mx2 = 3.6, Mx

2 = 2.9, 910 mJ/pulse, 4.5 mm x 6.7 mm

Mx2 = 2.5 , Mx

2 = 2.5

970 mJ/pulse, 5.0 mm x 6.8 mm

Mx2 = 3.2, Mx

2 = 2.4,

FIBERTEK, INC.

COLD1

WARMUP2

FAULT3

HPWR6

LPWR5

DIAG7

ARMED4

Power-up WARMUPFAULTARMEDLPWRHPWRDIAG

ARMEDLPWRHPWRDIAG

LPWRHPWRDIAG

CNTRL INITIALIZE

CNTRL LASERDISARMCNTRL HTRSON

CNTRL CLRINT

CNTRL LASERARM CNTRL LPWRMODE

CNTRL HPWRMODE

CNTRL DIAGMODE

CNTRL LPWRMODE

CNTRL HPWRMODE

CNTRL STOP

WARMUPARMEDLPWRHPWRDIAG

Any activefault

“1”

“4”

“-” (hyphen)

“D”

“7”

“2”

“8”

“C”

“C”

“A”

“A”

Blue text indicates alternative command characters when operating laser system from Hyperterminal serial interface

Raytheon Laser TransmitterModes and Power Consumption

28 W

32 W

687 W

687 W

687 W

87 W

FIBERTEK, INC.

COLD:Control electronics onHeaters offFaults suppressedDiode power supplies offAll diode & QS pulses off

WARMUP:THG and SHG heaters onFaults acknowledgedDiode power supplies offAll diode & QS pulses off

FAULT:Active fault detected/latchedHeaters on (unless heater fault is active)Diode power supplies offAll diode & QS pulses off

ARMED:THG and SHG heaters onTHG and SHG at nominal temperaturesFaults acknowledgedSeed laser onDiode power supplies onAll diode & QS pulses off

HPWR:Heaters onFaults acknowledgedDiode power supplies onAll diode pulses on, nominal PWQS onFull optical output power (after ramp-up)

LPWR:Heaters onFaults acknowledgedDiode power supplies onAll diode pulses on, nominal PWQS onLow optical output power

DIAG:Heaters onFaults acknowledgedDiode power supplies onAll diode pulses onQS offNo significant optical output

Raytheon Laser TransmitterState Definitions

FIBERTEK, INC. Raytheon Laser Transmitter Measured System Performance

Current system, 100% duty cycle, 50 Hz operation

Total DC power consumption (nominal 28 V) at 45.6 W (912 mJ/pulse @ 50 Hz) 1064 nm

output was 687 W (27.7 V, 24.8 A)

6.6% system level wall plug efficiency @ 1064 nm

Laser mass - 43 kg

Laser volume - 10 cm x 42 cm x 69 cm = 29,000 cm3

Preliminary 355 nm results - 300 mJ @ 50 Hz

2.2% system level wall plug efficiency @ 355 nm

Expected 355 nm results - >410 mJ @ 50 Hz (>45% THG)

>3% system level wall plug efficiency @ 355 nm

FIBERTEK, INC. Raytheon Laser Transmitter Alternate Duty Cycle Operation

Measured 1064 nm output during typical Off/On cycle

“Off” operation is in Armed mode (87 W)

“On” operation in HPWR mode (687 W)

88% of full power is reached in 1.5 minutes

93% of full power is reached in 2 minutes

10% duty cycle - 147 W average power - 687 W peak power

50% duty cycle - 387 W average power - 687 W peak power

100% duty cycle - 687 W average power - 687 W peak power

1064 nm power vs. time after Armed to High Power transition

Time (minutes)

0 2 4 6

1064 nm output power (W)

0

10

20

30

40

50

FIBERTEK, INC. Raytheon Laser TransmitterHarmonic Generation Status

Second harmonic generation - 25 mm Type I LBO

- Achieved 31.4 W of 532 nm output from 45.6 W of 1064 nm input

- 69% conversion efficiency

Third harmonic generation with 10 mm Type II LBO- Achieved 13 W of 355 nm output from 45.6 W of 1064 nm input

- 28% conversion efficiency

Third harmonic generation with 25 mm Type II LBO- Achieved 15 W of 355 nm output from 45.6 W of 1064 nm input

- 33% conversion efficiency

Results suggest back conversion may be occurring in 25 mm THG crystal

Additional modeling and tests are underway to clarify lower than expected THG

FIBERTEK, INC. Direct Detection Winds LIDARLaser Transmitter Status in 2006

Demonstrated >900 mJ/pulse from a single frequency 1064 nm pump laser operating at 50 Hz

with good beam quality

Demonstrated 33% conversion to 355 nm to achieve 300 mJ/pulse at 50 Hz >45% conversion still anticipated

Acceptance testing of risk reduction engineering model in a space qualifiable, conductively cooled

package in July

Amplifier tests to demonstrate scaling to 100 Hz in August with Air Force SBIR funding

Performance characterization and testing at Raytheon Space and Airborne Systems in Q3 of 2006

Life testing and characterization in Q4 2006 and beyond at Raytheon.

Demonstrate TRL 5 in 2006

FIBERTEK, INC.

Acknowledgements

BalloonWinds laser transmitter was funded by NOAA BalloonWinds

Program through UNH and MAC

Space Doppler Winds LIDAR risk-reduction laser transmitter was funded by

Raytheon Internal Research and Development (IRAD)

NASA support through the SBIR and Advanced Technology Initiative

programs

Air Force SBIR funding for 100 Hz laser development