Ippen nes osa 9-15-11

Clocks, Combs and OAWG

MIT Optics and Quantum Electronics

Erich P. Ippen

Massachusetts Institute of TechnologyCambridge, MA 02139

[email protected]

NEOSASeptember 15, 2011

Outline


Femtosecond lasers – few cycle pulses

Carrier envelope phase control

Optical frequency combs

Arbitrary optical waveforms

Applications

Clocks

Precision sampling and timing

The 5-fs Ti:sapphire Laser

Kerr lens modelocking (KLM)Double-chirped mirrorsAll-solid state, prismless cavity


5 fs = less than 2 cyclesOctave-spanning spectrum

Under Each Pulse is a Short Waveform

2nGL/c

The electric field waveform slips under the envelope from pulse to pulse – if group delay and phase delay differ.


Carrier-envelope phase slip

-80

-70

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RF

po

we

r sp

ect

rum

(d

Bm

)

200150100500

Frequency (MHz)

RBW: 100 kHz

fCE fR - fCE

BBO

570 nmfilter

PBS

RFspectrumanalyzer

PMT

Second harmonic generation

Control Over the Optical Phase

Carrier-envelope phase stabilization

An optical clockwork !


The optical frequency is an exact multiple of the pulse rep-rate.

A Clock

an oscillator a clockwork

Pendulum - Christiaan Huygens 1656

Chronometer - John Harrison (H4) 1761 (10-6 ~ 1 sec/ 9 days )

Quartz - W. Marrison, Bell Labs, 1928 (10-8 ~ 1 sec/3yrs )

Cesium atom - 1955 (10-10 ~ 1sec/300yrs)

Hg ion – 5x10-18 ~ 10sec since big bang

Atomic fountain - NIST-F1 (1.7x10-15 ~ 1sec/20Myrs)

and


From the 9.192 GHz Cs frequency standard to the 456 THz (657nm) Ca transition

Clockwork by Frequency Multiplication

1999

10-14 accuracy


10 lasers8 phase-lock loops

The Clockwork in the Frequency Domain

2 1 1g g

1mc mc f f f

2n L 2 L2f

n


d

dt

lasermodes

exactmultiples

of frep

1f 2f

repg

cf2n L

12f

2nd harmonics

f

1f-to-2f frequency locking

Octave-spanning frequency comb

This locks the rep rate to the optical frequency. Still need an optical reference.

Locking to the 3.39m HeNe Reference via DFG

g

c2n L m

g

mcf

2n L

He-Ne/CH4

Laser

3.39m

TransportableStability ~ 10-14

Difference frequency generation in PPLN

1f 2fDFG

2 1 rep reff f mf f

refref

c 3.39 mf


A Portable Optical Frequency Reference

Monolithic“sitall / zerodur”

resonator

• Compact• Ultrastable (< 10-14)• Transportable

Phase- locked He-Ne laser

3.39 m output


Mikhail Gubin, Lebedev Institute

Methane-stabilized He-Ne Laser: = 3.39m

L

1GHz Ti:sapphire Laser Frequency Comb


CEO locked

Frequency referenced

• 1f-to-2f in LBO

• CH4- stabilized HeNe

Optical Arbitrary Waveform Generation(OAWG)


Amplitudes and phases of all these frequencies are now determined. How about:

Completely Arbitrary Waveforms

G

ncf

2n L

G

mcf

2n L

G

cf

2n L

Fast modulator array

Spectrum lockedto “absolute” grid

Arbitraryelectrical field

waveform !


Pulse-to-pulseAM & PM

f

t

Arbitraryspectrum

Optical Arbitrary Waveform Generation

Sufficiently complicated temporally varying spectral phase masks create encoded optical signals.

Dispersion matchedgrating-lens pairs

Grating-lens pairs withphased mask inserted

The basic idea (Heritage and Weiner)

• A grating disperses the broad spectrum of an ultrashort pulse.• A phase and amplitude mask is inserted into the Fourier plane.• A second grating recombines the modified spectrum into a “shaped” waveform.

The advanced integrated version (UC Davis)

AWG1 AWG2

Phase modulators

IN OUT

Bond pads

Delay lines

AWG1 AWG2

Phase modulators

IN OUT

Bond pads

Delay lines

Modulatorarray

ArrayedWaveguide

Grating

In current technology, a small band of frequencies passes through each modulator element.


InP Encoder: 10channel

14.2 mm


UC DavisS.J. Ben Yoo et al.

Time (20ps/div)Time (20ps/div)

Trial output waveforms

10.7

mm

PMAM

Packaged InP OAWG(10 Ch AM+ 10 Ch PM) x 10 GHz


InPhi & UC Davis

1.5cm DCM11G

1% Inverse Gain OCDCM11G

1.5cm DCM11G

2.28mm Ti:Sa

5.5 GHz

1.5cm DCM11G


1.5cm DCM11G 2.28mm Ti:Sa

3.3 GHz

10 GHz0.75cm

DCM11G


0.75cm DCM11G

2.28mm Ti:Sa

Route to 10 GHz

• Precise dispersion compensation • Gain flattening• Optimized output mirror•Tight focusing; low loss


Mode Matching

Optics

Balanced Detector

Brewster Plate

PBS

λ/4

4%BS

Loop Filter

Piezo Driver

Output10xf

Piezo

ML Laser

LaserRep Rate: f

Super-invar

Hänsch-Couillaudlocking method

• F = 156 => 30dB sidemode suppression• F = 2100 => 55 dB sidemode suppression

J. Chen et al. Opt.Lett.32, 1556, 2007


Alternate Route: 10 x Rep-Rate Multiplication by Filtering

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RF

Spectr

a (

dB

m)

1086420

10x F = 2100

MIT Optics and Quantum Electronics Group

+d1

+d2

frep

2frep

2frep

4frep

Interleaver 1

frequency comb

f

f

f

tTR

t

t

frep

pulse train

4frepTR/4

Interleaver 2

Rep Rate Multiplication withMonolithically Integrated Interleavers

19

2 4 6 8 10

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0

Frequency (GHz)

Tra

nsm

issi

on

(d

B)

c=50%idealc = 60%

• Thermal tuning for optimizing• delays• coupling coefficients

• Side-mode suppression limited by• offsets in coupling coefficients• waveguide dispersion

M. Sander et al, CLEO 2011: CThY5

GHz Er:Fiber Laser Technology


Wider Goal: Two Octaves of Frequency Comb

Ti:sapphire Er/Yb glass/fiber

0.5 m 1.0 m 1.5 m 2.0 m

3.39 m /2

f-to-2f + DFG f-to-2f + DFG

repg

cf 10GHz2n L

• More power per comb line• Facilitates demultiplexing via AWG

HeNe-CH4

3.39mreference for DFG


22

1-GHz Er-doped Fiber Laser

121x94x33mm3

Poutput = 27.4 mW

Wintracav = 283 pJ

Ppump = 380 mW

967.1 967.7-100

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0

frequency (MHz)

a) b)

c) d)

1 2 3 4 5 6 7 8 9 10-70

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0

frequency (GHz)

inte

nsi

ty (

dB

m)

1540 1560 1580 16000

0.2

0.4

0.6

0.8

1

wavelength (nm)

inte

nsi

ty (

a.u

.)

17.5nm

sech2 fit

measured

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2

4

6

8

time delay (fs)

IAC

(a.u

.)

1.54x187fs

187 fs pulses17.5 nm BW


SBR

Partial Reflector OC 10%

OutputErbium Fiber

(92mm)

FC/PC connector

WDM

977 nm

SMF28e(11mm)

Integrated Femtosecond Waveguide Laser

4 cm 5cm10% out

outputLoop: 16 cmSBRpump

1520 1550 1580

-2000

0

2000

80

90

wavelength (nm)

a)

b)

refle

ctan

ce (

%)

disp

ersi

on (

fs2 )

70

100

4 cm 5cm10% out

outputLoop: 16 cmSBRpump

1520 1550 1580

-2000

0

2000

80

90

wavelength (nm)

a)

b)

refle

ctan

ce (

%)

disp

ersi

on (

fs2 )

70

100

4 cm 5cm

10% outoutputLoop: 16 cmSBRpump

• Integrated gain + dispersion compensation• Integrated pump coupling• Integrated loop mirror/output coupler• Butt-coupled SBR

44x18 mm2

• 400 MHz rep rate• 440 fs pulse duraton



• High power femtosecond amplifier• Octave-spanning continuum generation: = 1m - 2 m

1.55 m oscillator1 GHz, 200fs, 20mW

Output100fs2 W

PC

SMFPre-chirp Fiber

HNLFISO

Pre-Amplifier

PC ISO WDM

10W Raman Fiber Laser

LiekkiEr-doped Fiber

SMFPost-chirp

1480nm PUMP

Lens

980 nm

LiekkiEr-doped Fiber

(83 mm)PUMP

ISO

980 nmCollimator

DichroicLens Lens

SBROC(5%)

PZT

AOM

Lens

LoopFilter

~

PD

Amp

BPF

LO

Feedback Control Electronics

DFG

HeNe

SHG(f-2f)

LoopFilter

~

PD

Amp

BPF

LO

Feedback Control Electronics

Positive dispersionhigh power amplifier

1 GHz Er-Fiber Comb

D. Chao et al, to be published

1 GHz Octave-Spanning 1µm-2µm Continuum


1012nm7.09mW

2024nm65.37mW

1 GHz Source

1 GHz Supercontinuum

1082nm8.56mW

1590nm47.02mW

1f-2fDFG

• High field and coherent control science

• Optical coherence tomography

• Ultrahigh-resolution 3-D LADAR imaging

• Multi-dimensional spectroscopic sensing

• Bistatic LADAR

• Novel coherent optical communications

• Impairment avoidance in fiber communications

Some Applications


Application: Photonic analog –to- digital conversion

• Amplitude fluctuations of sampling pulse can be cancelled by balanced detection

• Resolution and dynamic range limited by timing jitter

• Modelocked lasers can achieve quantum-limited jitter

High Resolution Optical Sampling


optical sampling pulseI(t)

voltage waveformV(t)

timing jitter

V(t)

E-O Modulator

• Optical pulses sample analog signal on an electro-optical modulator

voltage waveform

Precision Sampling for ADC

G.C. Valley, Opt.Exp. 15, 1955 (2007)R. H. Walden IEEE J.Sel.Areas in Comm 17, 539 (1999)

ADC limited by timing jitter in sampler


The Walden Wall

• 4mm x 4mm chip

•20 HIC ring filters with 8 m radius, 20 nm FSR

• SiGe detectors with 2 GHz BW, 100 nW NEP

• Analog Si modulator bandwidth 50 GHz

• Ultra Low-jitter direct optical sampling

Kaertner, Ippen, Hoyt, Smith, Ram, MIT Lincoln Lab

40 Gs/s 8-bit Optical Bit Interleaved ADC


Synchronization of a Large Scale X-Ray FEL


Kim et al., MIT/DESY

Acknowledgments

Andrew Benedick

Hyunil Byun

Jeff Chen

David Chao

Jonathan Morse

Michelle Sander

Jason Sickler

Franz Kärtner


Noah Chang

Jung-Won

Kim

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0.5

Frequency (GHz)

Spectral Domain

Inte

nsi

ty

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-3

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-1

0

1

2

3

ph

ase

(ra

ds)

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2000

4000

6000

8000

10000

12000

time (ps)

Inte

nsi

ty

Comparison of Chirped vs. Unchirped pulse

Chirp

No Chirp

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-3

-2

-1

0

1

2

3

Time (ps)

ph

ase

(ra

ds)

temporal phase

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500

1000

1500

2000

2500

time (ps)

Time Domain

Inte

nsi

ty

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0

20

40

60

80

100

Ch

irp

(G

Hz)

exp(-(n/3.5355)8) apodization, 2p radians of phase across spectrum

• 10 x 10GHz (10ps pulses)• Supergaussian amplitude apodized• 2p quadratic phase• Chirp over timeslot - 100GHz/100ps

Linearly Chirped Waveform – 10 Modes

Spectral domain Time domain – chirped pulse

Phase vs. time

Chirp

Amplitude

Initial vs. chirped pulse


Theory

100 x 10GHz (1ps pulses), Supergaussian amplitude apodized27p quadratic phaseChirp over timeslot - 1THz/100ps

Linearly Chirped Waveform – 100 Modes

-500 -400 -300 -200 -100 0 100 200 300 400 5000

0.5

Frequency (GHz)

Spectral Domain

Inte

nsity

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-3

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-1

0

1

2

3

phas

e (r

ads)

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2

4

6

8

10

12

14x 10

5

time (ps)

Inte

nsity

Comparison of Chirped vs. Unchirped pulse

Chirp

No Chirp

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-3

-2

-1

0

1

2

3

time (ps)

phas

e (r

ads)

temporal phase

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5000

10000

15000

time (ps)

Time Domain

Inte

nsity

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0

200

400

600

800

1000

Chi

rp (

GH

z)

exp(-(n/1490.712)10) apodization, 27p radians of phase across spectrumSpectral domain Time domain – chirped pulse

Phase vs. time

Chirp

Amplitude

Initial vs. chirped pulse


Linearly Chirped Waveform 10-Modes

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0.2

0.4

0.6

0.8

1

Inte

nsity

(au

)

-50 0 50-3

-2

-1

0

1

2

3

Time (ps)

Pha

se (

rad)

Blue Curve – Target Intensity Black Curve -- Measured IntensityBlue dots – Target PhaseRed Curve – Measured Phase

Circles – Target Intensity Black Stems -- Measured Intensity Blue X – Target PhaseRed Dots – Measured Phase

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0.2

0.4

0.6

0.8

1

Frequency (GHz)In

tens

ity (

au)

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-1

0

1

2

3

Pha

se (

rad)


Experiment

Ippen nes osa 9-15-11

Technology

Transcript of Ippen nes osa 9-15-11