Ultrashort Optical Pulse Shaping - National Tsing Hua ...mx.nthu.edu.tw/~cbhuang/Course/Topic_4_Pulse_Shaping_ppt.pdf · Outline Pulse shaping basics SystemissuesSystem issues Pulse

IPT544000 Selected Topics in Ultrafast Optics

Ultrashort Optical Pulse Shaping

Chen Bin (Robin) HuangChen-Bin (Robin) Huang

Institute of Photonics Technologies

National Tsing Hua University, Taiwang y,

Various slides selected from invited talks by Prof. Andrew M. Weiner at Purdue University under permission

Outline

Pulse shaping basics System issues System issues Pulse shaper theory Programmable pulse shaping using liquid crystal modulators

Group-of-line regime Line-by-line regime

Other pulse shaping approaches Other pulse shaping approaches Direct space-to-time shaping Acousto-optic modulators Time lens shaping Deformable mirrors

Applications Applications

2

Shaping basicsShaping basics

3

Linear filtering

convolution

4

Femtosecond waveform synthesis

Fourier synthesis: parallel spatial/spectral modulation Diverse applications: optical communications, coherent controls,…. Pulse width range from ns to below 10 fs

Pulse shaping: control of time-domain envelope function

Spatial LightModulator/ Mask

5

Pulse shaping tutorial

k

kmtjkta ]exp[)(

0~

Phase

0~

0 mtime

doesn’tmatter

Amplitudecontrol

0~

In Phase

tens

ity

0~

0 mm

timein Phase

control

60~

Shaping data

Temporal analogy to Young’s double slit (fixed mask) Highly temporal structure by simple spectral phase and

amplitude control

2 6 THz2.6 THz

Time window

7

Synthesis of femtosecond square waves

Using fixed grey-level lithographically defined mask

How to generate gray level amplitude control?How to generate gray-level amplitude control?

Ripple:truncated spectrum

8

Shaping using spectral phase control

Inherently no loss!

9

Phase-only filtering

period: fburst duration: f

O-CDMAO CDMA

10

Selected chronology of F-T shaping

11

Selected chronology of F-T shaping (cont.)

12

Line-by-line shaping and lots more ongoing projects since 2005!!

System issuesSystem issues

13

Control strategies

Open loop vs. adaptive control

14

Adaptive pulse shaping

Interferometric intensity autocorrelation Monitoring for maximum SHG yield

15

Pulse shaping in amplified systems

16

SLM

Pulse shaper theoryW ill f d t il d i ti tiWe will perform detailed investigations

over the 4-f shaper

17

Pulse shaping theory: basics

Linear filtering system: infinite resolution

18

Pulse shaping theory: diffractions

Spectral smearing due to finite beam size

)()( xGxM

19

Waveform complexity

Bandwidth vs. minimum duration

Complexity: =B/df=T/tHigher complexity: larger beamHigher complexity: larger beam,

more dispersive grating, shorter input pulse

20

Phase to amplitude conversion

Due to diffraction

21

We will see a more evident example later

Programmable shaping:Liquid crystal modulator pulse shaping

Group-of-line regime

22

Liquid crystal array

Phase or amplitude control

in

LCM

out )(Vj yeEE Why LCM

23

ininout

yeEE Why LCMy-oriented?

LC phase array

Nematic LC

Mi i i d ff tMinimize edge effect

24

Shaping: Group-of-Lines

Past: Group-of-Lines

25

“Dynamic” phase shaping

Limited to LC response time (~ 10 ms)

20 Hz rate switching

Question: how to generate pulse doublet?

26Weiner, Leaird, Patel, Wullert, Opt. Lett. 15, 326 (1990)

Question: how to generate pulse doublet?

Dispersion compensation

Approximate dispersion compensated using SMF and DCF For fs applications, dispersion and dispersion slope must be matched Fine-tuning as spectral phase equalizer

27

Higher-order phase correction

Mainly cubic

28

Spectral phase of 400 fs, 10-km experiment

Evident quadratic and cubic phase Can be compensated simultaneously

Modulo of 2

29

Post compensation of CPA system

30

{Phase + Amplitude} Shaping using LCM

2 orthogonal LC layers

iny

inxVVj

outy

outx

EE

jj

eEE

)cos()sin()sin()cos(),( 21

)]()([21

2211 VV )]()([21

2211 VV

Linear polarized input + output polarizer

xVVeEE VVjinout ˆ)],(cos[ 21),( 21

31

phase amplitude

{Phase + Amplitude} shaping examples

Nearly arbitrary pulses

Time-window

32

Question: how to generate these waveforms?

LCM shaping summary: Group-of-line

Gray-level amplitude and phase control Pixellated spatial modulation (128, 512, 640, more than 10,000) Quasi-static mask Reprogramming time~ 10 ms or greater

Low attenuation Low attenuation Phase and amplitude response needs calibration Time window that limits waveform spaceTime window that limits waveform space

33

Programmable shaping:Liquid crystal modulator pulse shaping

Line-by-line regimeLine by line regime

2222

22

)2

exp()(in

a

wttg

Increase spectral resolution

)0(cos2ln2

i

inwin cd

wT

Increase spectral resolution increase time window

34

Line-by-line shaper Reflective grating based shaper

f f

1200

LCM

f f~1000 mm focal length

1200 lines/mm Grating

Lens1542.6 1542.7 1542.8

Wavelength (nm)

2.6 GHz

MirrorLens

CollimatorTelescope 2 1

Circulator~18 mm diameter b Input Combs

Polarization Controller

p 2 1

3

beam

Polarizer

Input Combs{5,9,10}-GHz

1pixel{4.5, 5}-GHz

Output shaped pulse

35

Shaping: Line-by-line

Line-by-Line

Jiang, Seo, Leaird, Weiner, Opt. Lett. 30, 1557 (2005).

y• Overlapped waveforms• Step closer to true optical arbitrary

(O AWG){Pulse shaping} + {Combs}

waveform generation (O-AWG)frep

• Increase shaper resolution

frequency

• Increase shaper resolution• Increase comb spacing

New physical insight:Shaped waveforms are sensitive to

T/2

Shaped waveforms are sensitive to comb offset frequency drifts!

timeT=1/frep0

36

Sensitive to comb offset shifts

Comb-offset frequency fluctuates

Time-domain view fluctuates

2 lines of a harmonically mode-locked Er-fiber [email protected] GHz

Phase between pulses

Multiple tracesof OSA

frep

Phase between pulsesfluctuates

Frequency (GHz)0 20

of OSAOverlapped intensity fluctuates

=0

-2 -1 0 1 2

t/T

Maximum

noise

37

t/T

Filter function: H()1

dxexMw

H wx

20

2)(221

20

)(2)(

Huang, Jiang, Leaird, Weiner, Opt. Express 14, 13164 (2006)

Frequency-domain view

10

0

(dB

) ExpSim

=0

30

-20

-10

|H(

)|2(

=0Sim

Frequency (GHz)-20 -10 0 10 20-30

= Frequency discriminator

0

dB)

Exp

= Frequency discriminator

-20

-10=

H(

)|2(d

pSim

38

-20 -10 0 10 20-30

Frequency (GHz)

|H

Correlating Two Pictures Intensity variance due to

Freq-domain: H() discriminatorTime domain: delay Time-domain: delay

=0===3=H()( )=0=25%=50%

Frequency-Domain

2( f )Time

2

)(

cos2(frept)

=0)

Time-Domain

39

=25%=50%

Why repetition change!

Waveforms for sensitive monitoring 2 lines spaced by 2frep

Frequency vs. time-domain viewCan be extended to Nf

Periodicity conversion Can be extended to Nfrep

0 1-1-2 2 1

0

0.5

Pow

er

rep

T/21

f/frep

-2 -1 0 1 20

0.5

1

Inte

nsity

-1 -0.5 0 0.5 10

t/T

I

40

R()≡I(0)/I(T/2)These observations were experimental verified

Question

So, if we don’t have time window, but we still have phase to intensity conversionbut we still have phase-to-intensity conversion,

where are the diffracted energy?

41

Comb source alternatives Self-referenced mode-locked lasers

Highest frequency stabilityN t il bl t ffi i tl hi h t ( til tl ) Not available at sufficiently high rates (until recently)

Pulse shapers with higher resolution spectral dispersers? Filter to increase comb spacing (NIST, MIT..) parameter mismatch

Hybrid mode-locked lasersP f t bilit l k f ff t f t i bilit Poor frequency stability, or lack of easy offset frequency tuning ability

Phase-modulated CW sources Phase modulated CW sources Moderate frequency stability Easy tuning of offset frequency

Li it d ti l b d idth ( b h d b li ti )

(enabled experimental tests of pulse shape changes due to comb offsets)

Limited optical bandwidth (may be enhanced by nonlinear propagation)

42

Broad BW, frequency stable

Source alternative: PMCW

Phase-Modulated Continuous-Wave laser frequency comb =Vp/Vmodulation index

V cos( t))}cos(exp{)( 0

0 tjeEtE reptj

Vpcos(rept)

})(exp{)( 0 tmjJ repm

m

modulationBessel’s

0.49GHz comb@2V

frequencyesse sseries

Benefits:

0

0.2

d (a

.u.)

Benefits:Relative high frequency stability

No stabilization required!Ease of tuning

-0.2

0

Fiel

d

Disadvantage:Dispersion control required

Linewidth

43

-50 0 50-0.4

Frequency (GHz)

LinewidthPulse shape

10-GHz PMCW comb: Setup

0 0

IM LCM Dual-modulation Broader bandwidth, shorter pulse

-20

-10

(dB

m)

0

20

-10

0

PM RF

-40

-30

Spec

trum

-40

-30

-20

~7dB intensityi ti

PM

0

{Phase + Amplitude} control to 41 lines1541 1542 1543 1544

-50

Wavelength (nm)1540.5 1542 1544-50

40

Wavelength (nm)

variation

-20

-10

m (d

B)

-40

-30

Spec

trum

ExperimentalSuper-Gaussian

44

1540.5 1542 1544-50

Wavelength (nm)Huang, Jiang, Leaird, Weiner, Electron. Lett. 42, 1114 (2006).

High-rate pulse train generation

Phase correction Automated process

Intensity autocorrelation

22

)()()(

tItIG

Nonlinear pulse propagation Adiabatic soliton compression

22)(

)(tI

Dispersion-decreasing fiberPMCW -10

0-10

0

(dB

) 298 fs

seed pulses

D(0) D(L)

1520 1530 1540 1550 1560 1570-40

-30

-20dB

40

-30

-20

SHG

(45

1520 1530 1540 1550 1560 1570Wavelength (nm)

-60 0 60-40(ps)

5-GHz shaping using > 100 LinesJiang*, Huang*, Leaird, Weiner, Nature Photonics 1, 463 (2007).

5 GHz frequency comb with > 1000 lines starting from one

5 GHz O-AWG using 108 comb lines (1st time) Waveform complexity Pulses overlap Pulses overlap Closer to using self-reference combs

Planar Lightwave CircuitsLimited line number (10~32)

Limited line spacing (> 10 GHz)Miyamoto, et.al., Photon. Technol. Lett. 18, 721 (2006).

Fontaine, et.al, Opt. Lett. 32, 865 (2007).

46

Setup > 1000 lines comb generation through soliton compression

Adiabatic soliton compressionDispersion-decreasing fiberp g

Auto-correlationse)

270 fs

Line

ar

ar S

cale

B/di

v) 1 THz Input CW

-10 0 10

div

ty (

Line

Time (ps)-5 5

ity (1

0 dB

#1#1000

-200 -150 -100 -50 0Time (ps)

10 d

B/d

Inte

nsit

Inte

ns

1525 1525 5 1564 5 1565

47Time (ps)

-200 -150 0-50-100

Time (ps)

1520 1530 1540 1550 1560 1570Wavelength (nm)

1525 1525.5 1564.5 1565

> 100 lines shaping examples-(1)

Linear phase ramp delay of pulse locations Delay across entire period hallmark of line-by-line shaping

48

> 100 lines shaping examples-(2)

O-AWG using intensity/phase over 108 lines

Cross-correlation

.)

0

ensi

ty (

a.u

Inte

1536 1537 1538 1539 15400

Wavelength (nm)1535

49

Line-by-line shaping summary

Line-by-line shaping removes the time-window limitation!Comb frequency stability shows up in shaped waveform intensity noise Comb frequency stability shows up in shaped waveform intensity noise Time and frequency domain views “Quiet” and large spacing combs preferred

Allows optical arbitrary waveform generations

50

Other pulse shaping:Direct space-to-time shaping

grating 4-f shaper

51

DST shaping

Output temporal profile a directly scaled version of input spatial mask Changing slit-lens distance: frequency modulation without affecting time-

domain profiledomain profile Space (parallel) Time (serial) processing

52

DST shaping data

53

Shifting center frequency

Sliding slit location Why amplitude variations?

]'exp[)()()(ˆ

txjtstate a

out

54

1. What happens if we move the slit off the focal plane?2. What if radius of beam not infinite?

Other pulse shaping:Acousto-optic modulator

Photo-elastic effect: RFPZT acoustic wave index grating (=v/)

55

AOM shaping

Spectral amplitude and phase control via diffraction off the AO crystal Requires electrical driving signal Limited response time, suitable for amplified systems

t

v~105 cm/s for TeO2

)()()(AO

AOinouttstete

Selected from long pulse sequence

56

Frequency swept pulses

Hyperbolic tangent frequency sweep

)h()()(

)(sech)( )1(

ttte i

)tanh()()( tt

t

Spectrally/temporally resolved up conversionp y p y p

57

AOM shaping summary

Independent gray-level amplitude and phase control Continuous spatial modulation (time-bandwidth product > 1000) Travelling-wave mask Reprogramming time~10 s

High attenuation High attenuation Acoustic attenuation must be calibrated Complex electrical functions neededComplex electrical functions needed

58

Oth l h iOther pulse shaping:Chirp processing

)()()(2jkx

Space-Time duality

)2

exp()()(

2jtz

jxsxs inout

59

)2

exp()()(2z

jttata inout

Direct frequency-to-time shaping

Frequency-dependent time delay Large dispersion regime

)()(

)()( 2 2

2

tAejzta ztj

)(2

),(22

2

zAe

zzta

60

Arbitrary mmw generations

~90 ps/nm

1 25G 2 5G 5G

Time-aperture: optical bandwidthDispersion: sign of chirp

1.25G 2.5G 5G

61

Fast RF waveform measurement

Reversed thinking: time frequency mapping Different temporal samples impressed onto different spectral components Resolve and detected using grating + detector array

Optical modulator

62

Other pulse shaping:Time-lens shaping

fdd imgobj

111

fimgobj

ttimgobj

)()(

11

63

gj )(2

)(2

Time microscope Analogy to spatial lens Mt=100

G t f i l h t l t!2)(

2 176.0 psobj Great for single shot pulse measurement! 2)(

2 6.17 psimg

64Bennett, Kolner, Opt. Lett. 24, 783 (1999)

Optical oscilloscope on Si chip

Time-lens concept 1 nm shift 5.2 ps shift

65

Foster et.al., Nature 456, 81 (2008).

Other pulse shaping:Movable and deformable mirrors

66

Rapid scanning optical delay line

Roughly kHz rate Optical phase and delay decoupled

Same control used for Ti:S combs!!

Time-space coupling

Same control used for Ti:S combs!!

67

Pulse compression

68

Selected applications:Communications and coherent control

69

Planar lightwave circuit shaper

Silica based devices

70

Wavelength domain multiplexing

71

Dark solitons in optical fiber

1.4 m fiber

72

Millimeter-wave generations

73

Spectral tailor of UWB

Duration: RF BWCycle: RF center frequency

74McKinney, Lin, Weiner, IEEE Trans. Microwave Theory and Tech, 54, 4247 (2006)

Rapid reprogrammable RF-AWG

Rapid switching between two waveforms 2 CW lasers

2 intensity modulators (BERT to select) 2 intensity modulators (BERT to select) Comb generator (phase modulator + line-by-line pulse shaper) 60 GHz bandwidth photo-detector Monitor optical spectrum, RF time-domain waveform, RF spectrum

-21

23-1 0

-21

23-1 0

{-2,1,2,3}=

5dB

/DIV

-3 1 31 0 -3 1 31 0

1540.8 1541.2 1541.6 15425

a b

75

Wavelength (nm)

Huang, Leaird, Weiner, Opt. Lett. 32, 3242 (2007).

10-GHz programmability results-(I)

Q=[1111 0000]

8

-4

0

-16

-12

-8Extinction

~16 dBPhase modulation

-500 0 500t (ps)

5dB

/DIV

1541 1542Wavelength (nm) Frequency modulation

(a.u

.)

(a.u

.) Ia(t) Ib(t)

nten

sity

nten

sity

5dB

/DIV

76

In

-500 0 500In

Time (ps)

1541 1542Wavelength (nm)

10-GHz programmability results-(II) Triangular waveform updates

Dual-modulation scheme Cubic spectral phase Cubic spectral phase

V a.u.

)28 lines per comb

5dB

/DIV

nten

sity

(aIn

y (a

.u.)

y (a

.u.)

Inte

nsity

Inte

nsity

77

Goal: remote MMW carrier generation

Radio-over fiber (low loss) Photonic MMW generator

Sub-ps pulses > 300 GHz repetition-rates Dispersion pre-compensation to arbitrary SMF link length Dispersion pre compensation to arbitrary SMF link length

EndArbitrary SMF length-users

MMWsignal

ti

Remote photonic MMW

t generationgenerator

78

These targets are also challenges

Remote photonic MMW generator

Phase-modulated CW laser frequency comb Line-by-line optical pulse shaper: {amplitude, phase}-controls

f(frep)-1

f

ff

LCM Lens

frep

f

Reflective line-by-line pulse shapert

( p)

Line-by-LinePulse Shaper

CWLaser

PhaseModulator

fMirror

G iSpectral

f

frepPA

(Nf )-1 Free Space

GratingSpectralLines

Collimator

TelescopeCirculator

PCInput

Polarizer

SMF

t

(Nfrep) Free SpaceFiberShaped

Output

Shi H d P NPG A i M t 3 41 (2011)

79Shi, Huang, and Pan, NPG Asia Materials 3, 41 (2011)

t Shi, Huang, and Pan, NPG Asia Mat. 3, 41 (2011)

Repetition-rate multiplication (RRM) Amplitude filtering Phase filtering

P i di h t l lf i i t l T lb t ff t Periodic phase: temporal self-imaging, temporal Talbot effect

Huang and Lai, Photon. Technol. Lett. 12, 167 (2000)2( ) s k T0

Azaña and Muriel, J. Sel. Topics Quantum Electron. 7, 728 (2001)( )k kN

0TN RRM condition

breaksSMF

Mode-lockedlaser

FBGRRM train

SMF

laser

80

Short pulse delivery: dispersion issue

Residual β3 term

Dispersion compensation fiber

SMF

Mode-locked

DCF

Mode-lockedlaser

2 332( ) [ ]L

β3 term compensated DCF + Pulse shaper

( ) [ ]2 6SMF L

β3 term compensated50 kmSMF DCF

Mode-lockedlaser

Pulseshaper

81Jiang, Yang, Leaird, and Weiner, Opt. Lett. 30, 1449 (2005)

Line-by-line pulse shaping

Jiang, Huang, Leaird, and Weiner, Nat. Photonics 1, 463 (2007)

Independent control over each comb line

( ) 2 ( )N

DCF needed?

( ) 2 ( )SMF k k rem kN Integer Talbot effect

500

600

ase

(2)

200

300

400

500

Pha

0

100

-10 0 10Line number

Severely broadened single pulseDemands high

source temporalcoherence

82

t t

Experimental results

31GHz PMCW Comb

0 ,25( ) ( ) ( )LCM rem km 0( ) ( )LCM

31GHz PMCW Comb

0 93 ps0.93 psDe-convoluted

83

Remote ultrahigh rate pulses

124GHz Shaper-RRM

π π π

0 ,25( ) ( ) ( ) ( )LCM rem RRMkm

4x-RRMPhase: 0 , 0 , π , 0

00 0 0 0

0ππ

2x-RRMPhase: 0 , π

2

00 00

π

2

π

2

π

2 π

2

2

Huang and Lai, Photon. Technol. Lett. 12, 167 (2000)

84

Impulsive stimulated Raman scattering

Single pulseexcitationPhase only shaping

85

Coherent control on TPA yield

2Asymmetric phase: no change! 200

2 )]}2

()2

([exp{ djS Asymmetric phase: no change!

Cs: 6S1/2 8 S1/2

86

Soft X-ray generation

Solid: optimizedy Solid: optimized

inte

nsity phase

87

Polarization shaping

Brixner, et.al, Appl. Phys. B 74, S133 (2002)

88Aeschlimann, et.al, Nature 446, 310 (2007)

Summary

Shaper basics F-T shaper using fixed and programmable masks

Theoretical derivations Group-of-line vs. line-by-line

Other shaping methods Other shaping methods Theoretical derivations and examples

Applications in various diverse fields

89