large-scale laser spectral compression and its …...2012/03/26 · 2012/4/6 1 amo seminar,...

2012/4/6

1

AMO Seminar, Department of Physics, National Tsing Hua University

Chen-Bin Huang (黃承彬)

Large-scale laser spectral compression and its applications

Institute of Photonics Technologies

National Tsing Hua University, Taiwan

March 26, 2012

Ultrafast Photonics Lab

2

2012/4/6

2

Ultrashort optical pulse

Electric field

Carrier

Envelope function a(t)

( ) Re{ ) }xp( e oj ta tE t

0.8

1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

2( ) ( )I t a t

I(t) t

3

Ultrafast optics

Full-width half-maximum pulse duration t < 1ps

-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2

-1

pst

Optical pulse shaping

We can shape the optical waveform however you like

-200 -100 0 100 200Time (ps)

0 3 0 3

0

1Measurement

Calculation

Inte

ns

ity (

a.u

.)

4

-100 -50

0.1

0.2

0.3

Time (ps) 0 50Time (ps)

0.1

0.2

0.3

Jiang*, Huang*, Leaird, Weiner, Nat. Photon. 1, 463 (2007)Chuang and Huang*, Opt. Express 18, 24003 (2010)

2012/4/6

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Outline

Ultrafast 3rd-order nonlinear optics

Self-phase modulation

Optical solitonsp

Raman scattering

Self-steepening

Supercontinuum generation

Spectral compression

5

Summary

Nonlinear wave propagation equation

The inclusion of nonlinear polarization

22

0 2( )

DE E E

t

22 22

0 (1) 02 2 2NL

T

PE EE

z t t

0 (1) (1) LNL ND E P P D P

6

Scalar treatment

20 0 0 (1) 0 (1) 0 0( 2 2 ) ( 2 )NL NLD n n n n n E n n E

0 02NL NLnP n E

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Nonlinear propagation equation in waveguide

Basic formulation

222

1 20

2 2

ja a aj a a a

z t t

2

20 0

20 eff

nn

c A

optical Kerr term

NonLinear Schrödinger Equation

Lossless

Generalized NLSE

0 eff

222

2 20

0' 2

ja aj a a

z T

7

2 22 32

2 32 30

1

2 2 6 R

a a aA j a a jA j a a T a

z T T T T

( ) ( )

dispersion

SPM Raman

Self-steepening

Self-phase modulation (SPM)

No dispersion 2aj a a

z

2( , ) (0, ) exp[ (0, ) ]a z t a t j a t z Gives broadened spectrum

instantaneous frequency:

0.8

1

ectr

a

2( )( , ) ( )z t a z

t t

instantaneous frequency:

I(t)

t

8

-5 0 50

0.2

0.4

0.6

(THz)

Opt

ical

spe

in

st

t

max

max

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Optical solitons

For anomalous dispersive materials: 2 < 0

Dimensionless NLSE

Solution: solitons

22

2

1

2

a aj a a

Complete balance between dispersion and SPM

Pulse energy

22

0 0

( , ) sech( )exp[ ]2c

j zta z t P

T T

22U

9

gy

Soliton order

2

0

UT

02

2

peakT PN

Adiabatic soliton temporal compression

Dispersion control

Energy conservation

2

0

2U

T

0 2

0 2

(0) (0)

( ) ( )

T

T z z

Gives broadened spectrum

0


10

-60 0 60-40

-30

-20

-10

0

(ps)

SH

G (

dB

) 298 fs

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Higher-order solitons

N=2peakj P

N

jNP

2

2)122(

0T3500


L=z0/2 1220

jN

TTj

-3 -2 -1 0 1 2 30

500

1500

2500

3500

t (ps)

Pow

er (

W)

107

11

-1 -0.5 0 0.5 1x 104

0

0.5

1

1.5

2

2.5 x 107

Frequency (GHz)

Pow

er (

W)

Higher-order solitons

N=3

L=z0/4 L=z0/212000


-3 -2 -1 0 1 2 30

1000

2000

3000

4000

5000

t (ps)

Pow

er

(W)

6x 10

7

-3 -2 -1 0 1 2 30

2000

4000

6000

8000

10000

12000

t (ps)

Pow

er (

W)

6x 107

12

-1 -0.5 0 0.5 1

x 104

0

1

2

3

4

5

6

Frequency (GHz)

Pow

er

(W)

-1 -0.5 0 0.5 1x 10

4

0

1

2

3

4

5

6x 10

Frequency (GHz)

Pow

er (

W)

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Raman response

Delayed nonlinear phase delayed instantaneous frequency

Red-shift of the pulse power spectrum

Time-domain view


13A. M. Weiner, Ultrafast Optics (Wiley, 2009)

Fourier-transform properties

Raman response real F(-)=F*()

A single-sided function

Im{F()} < 0 for > 0

Frequency-domain view

Im{ ( )}F

200

300ReIm

Im{F()} > 0 for < 0

0 8

1

F()

Im{ ( )}s pF

14-0.5 0 0.5 1

-200

-100

0

100

0 10 20 30 40 500

0.2

0.4

0.6

0.8

f(t)

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Self-steepening

Gives rise to intensity-dependent group velocity

Dispersionless, only electronic response

a j 2

0

1 0'

a jj a a

z t

2

0

30

'

a aa

z t


0.6

0.8

1)

15

)'(v

ztfa 2

0

3 av

-4 -3 -2 -1 0 1 2 3 40

0.2

0.4

t/T0

I(t)

Soliton fission

Nth-order solitons will break into N fundamental solitons

Raman: soliton self-frequency shift (SSFS)

Self-steepening Gives broadened spectrum

Anomalousdispersion

red

Shorter,red-shifted

pulse


16Dudley et.al, Nat. Phys. 3, 597 (2007)

redslower

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Supercontinuum generation Supercontinuum generation


Summary

17

SC: Definition

What is SC?

Coherent light source having large bandwidth

Broadened input spectrum by nonlinear optical processes

Applications

Metrology, spectroscopy, sensing, ultrashort pulse……

18

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SC: History

Historical evolution

19www.bath.ac.uk/physics/groups/ppmg/research_pcf_scg.html

birth ofoptical frequency comb

tightly linked

SC: Major Nonlinear Processes

SPM

t

ALinst

2||

FWM

4321

2

SRS

ASSp 2

Elasticprocesses Inelastic

ProcessAlong with

SSFS+ SS

20

pI S

ISp 2

kM+kWG+kNL=0 p

AS

S

p

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Microstructured Fibers

Photonic Crystal Fibers(PCF)

Guided by photonic band-gapConfined within air

Effective indexConfined within material

Photonic Band-gap Fibers(PBF)

Microstructured Fibers(MF)

21Russel, Science 299, 358 (2003)

Variable MF Properties

Small effective modal area

Large nonlinearities!

Endlessly single-mode

Cladding index engineering

2 222.405eff co clV n n

Lattice pitch, not core diameter!

1500nm400nm 800nm

22G. Genty, Ph.D. Dissertation, (Helsinki University of Technology,2004).

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Variable MF Properties

Zero-dispersion wavelength (ZD) Core size

Dispersion relation Air-hole diameter Lattice

23Reeves et. al., Nature 424, 511 (2003) G. Genty, Ph.D. Dissertation

Comparison of MF Properties

Fiber\Properties SMF DSF DCF HNLF MF

Attenuation (dB/km) 0.2 0.2 0.45 0.7 80-240( )

Modal area (um2) 85 50 19 12 3

(1/W/km) 1.8 2.7 5 15 50

24

Much lower power is required to generate SC

Ability to tune L and NL properties

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First SC Generated using MF

Ranka, Windeler and Stentz (2000)

MF

PM

p = 790 nm

SMF

25Ranka et. al., Opt. Lett. 25, 25 (2000)

ZD=767nm

p

ZD = 767 nmt = 100 fsPp = 8 kWPav = 64 mWL = 75 cm

SC Generation in MF

Defining pumping modes

Anomalous

Normal Normal pumping

ersi

on (

ps/n

m/k

m)

0

-100

Anomalous pumping

Higher-orderS lit

26Wavelength

Dis

pe -200

-300

ZD

Solitons

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Anomalous pumping flow chart

Higher-order soliton formation

Soliton fission

Linear radiation wave (RW)

Stimulated Raman scattering (SSFS)

Later broadening

FWM + SRS for anomalous dispersion regime

SPM for normal dispersion regime

27wavelengthZD

p

Higher-order soliton: anomalous pumping

Effect of pump power

Wider, flatter

tP k

1.5kW

1.3 kW

N=40T

p = 850 nmZD = 806 nmt = 200 fs

L = 6 m

665.12

tPN peak

N=2

N=31220

jN

TTj

RW

28Ortigosa-Blanch et. al., JOSA-B 19, 2567 (2002)

SSFS

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Brief history

Our approach

Numerical and experimental results

29

Summary

Nonlinear processes spectral broadening

Self-phase modulation


Higher-order solitons: SPM, dispersion, FWM, SSFS, soliton fission

A. M. Weiner, Ultrafast Optics (Wiley, 2009)

30J. K. Ranka et.al., Opt. Lett. 25, 25 (2000)

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Applications

Highly spectrally bright coherent sources

Optical metrology, linear/nonlinear spectroscopy

ps pulse trains

Narrow-band, CARS

Different compared to spectral filtering

Energy re-distribution

Ideally loss-less

31

Spectral narrowing/compression

Earliest experimental observation

R. H. Stolen and C. Lin, Phys. Rev. A 17, 1448 (1978)

Physical insight explained

S. A. Planas et.al, Opt. Lett. 18, 699 (1993).

M. Oberthaler and R. A. Höpfel, Appl. Phys. Lett. 63, 1017

(1993).

SPM

( )inst

t

t

Instantaneous frequency

Pulse chirp, SPM and dispersion

32

Down-chirped pulse spectral compression

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Prior works

Various fiber types and input chirp conditions

Compression ratio

PublicationsFiber type (sign of 2)

Input chirp

Compression ratio

Shen et.al, JLT 17, 452 (1999) SMF (-) + 2

Washburn et.al, OL 25, 445 (2000) SMF (+) - 3.5

Limpert et.al, APB 74, 191 (2002) Yb-doped (+) - 16

Andresen et.al, OL 30, 2025 (2005) PCF (~0) - 21

33

Sidorov-Biryukov et.al., OE 16, 2502 (2008) HNPCF (-) X 7

Fedotov et.al., OL 34, 662 (2009) HNPCF (-) X 6.5

Nishizawa et.al., OE 18, 11700 (2010) CPF (-) X 25.9

Andresen et.al., OL 36, 707 (2011) HNPCF (+) - 5

solitonschirp-free, below soliton Ppeak

Soliton effect for spectral compression

Comb-profile fiber

19 segments of SMF and DSF

Large compression ratio of 25.9

Excellent side-lobe suppression

34N. Nishizawa et.al., Opt. Express 18, 11700 (2010)

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Adiabatic soliton temporal compression

Dispersion-decreasing fiber

Fundamental soliton

60 times pulse compression

outout in

in

D

D

35C.-B. Huang et.al., Opt. Express 16, 2520 (2008) K. R. Tamura et.al., Opt. Lett. 26, 762 (2001)

Our idea

Simply run the adiabatic soliton temporal compression in reverse!

Adiabatic soliton spectral compression

Simple idea, never realized!

DDF dispersion-increasing fiber (DIF)

Short pulse (wide spectrum) in, broad pulse (narrow spectrum) out

36

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Split-step Fourier method

Input pulse envelope

Spectral envelope

222

22

ja aj a a

z t

0a t( , )

F.T.

0A ( ) Spectral envelope

Dispersed spectral envelope

Dispersed pulse envelope

0A ( , )

220

2D

zA z A j

( , ) ( , )exp[ ]

I.F.T.

a z t( )

37

Dispersed pulse envelope

Dispersed, SPM pulse envelope

Now do iterations all the way to the output

Da z t( , )

2

D SPM D Da z t a z t j a z t z , ( , ) ( , )exp[ ( , ) ]

Adiabatic soliton spectral compression

Dispersion-increasing fiber

Ideal compression ratio = Dout/Din=22.5

5

10x 10

4

1 km in lengthDin=0.60 ps/nm/km

Dout= 13.5 ps/nm/kmLoss: 0.4 dB/km= 3.5 (W km)-1

TR=3 fsCompression ratio=4.5

205 fs input pulseBW: 13 nm

38

1540

1550

1560

1570

1580

0

0.2

0.4

0.6

0.8

1

0

Wavelength (nm)z (km)

NLSEby SSF

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Large spectral compression ratio

Positively chirped 305 fs input pulse

Explanation

Stability

20

Time-domain

4x 10

5

Spectral-domain Compressionratio= 12.5

39

-50

0

50

0

0.2

0.4

0.6

0.8

1

0

10

Time (ps)z (km)

1540

1550

1560

1570

1580

0

0.2

0.4

0.6

0.8

1

0

2

Wavelength (nm)z (km)

Experiment: setup

1 km in lengthDin=0.60 ps/nm/km

Dout= 13.5 ps/nm/kmLoss: 0.4 dB/km= 3.5 (W km)-1

MLFL

EDFA

DIF

DCF2

DCF1

90% Intensitycross-correlator

10%

PM5%

95%OSA

TR=3 fs

40

0

1

Delay (ps)-0.8 -0.4 0 0.4 0.8

350 fs

Wavelength (nm)1540 1560 1580

0

1

13 nm

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Experiment: results

Spectral compressionratio=15.5

41

Intensitycross-correlation

Experiment: wavelength tuning

Control of input power

Soliton order N: 1~1.4

aliz

ed s

pec

tra

42

No

rma

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Summary

Adiabatic soliton propagation in a dispersion-increasing fiber is a

simple means in achieving spectral compression

Positively chirped pulse provides better spectral compression ratio Positively chirped pulse provides better spectral compression ratio

if dispersion ramp is too large

Experiments for the first time: 350 fs chirped pulse in a 1-km DIF

Spectral compression ratio of 15.5

Temporal broadening

43

30 nm of wavelength tuning ability

H.-P. Chuang and C.-B. Huang, Opt. Lett. 36, 2848 (2011)

large-scale laser spectral compression and its …...2012/03/26 · 2012/4/6 1 amo seminar,...

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