Proposal to PAL from SPring-8~ Pulse-stacker-based square pulse (>10ｐｓ) shaping system ~Hiromistu Tomizawa
Accelerator Division,Japan Synchrotron Radiation Research Institute (SPring-8)

0. Intro. ~ Recent progress in UVUV-pulse (>10(>10 ps) shaping ~1. Macro-pulse (15~20 ps) generation withUV-pulse stacker
2. Passive micro-pulse preparation- Prism-pair UV-stretcher + Pulse Stacker

3. Adaptive micro-pulse preparation- UV- & IR-DAZZLER feedback sys.+ Pulse Stacker

4. Summary for generation of 15~20-ps
UV- Square laser pulse

０. ~10-ps pulse-shaping development in UV (~263 nm):In the year 2006, UV-shaping technologies are matured!

1. PAL developed Prism-pair UV-pulsestretcher (up to 6 ps with nice shape)
Korea
2. UV-pulse stacker was developed by
SP8 and commercialized for industry.
Japan
3. UV-Dazzler (AO) was completed (upto 5 ps) by Fastlite (L’ Ecole polytechnique) and commercialized.
France1. Macro-pulse (15~20 ps) generator(Pulse stacking to reach longer square pulse)
1-1. UV-Pulse Stacker

Sλ/2 waveplate

2～3 ｐｓPSP

4～5 ｐｓSPSPSPSP

16～20 ｐｓ

※ Entrance window should be double AR-coated !
※ Not utilize Brewster Window !
※ The polarization of the input UV-laser is rotated
45 degrees by the half lambda waveplate.
※ UV-laser is split into two equal portions by the each
cubic polarizer. But, consider QE deference between
S and P!!

SPSP SPSP

16～24 ｐｓ

1. Macro-pulse (15~20 ps) generator
1-2. Chirped pulse with deferent compressor length(in the case of SPring-8)
Changing compressor length,2.5-ps original pulse is generated！
Not that, laser pulse will bepositively chirped & stretchedthrough the silica material !

PSPSPSPTo avoid interferences on the plateau of stacked
macro pulse, S- and P- polarized pulses arealternatively positioned!

Positive⇨

S⇨

Negative

20 ps

1. Macro-pulse (15~20 ps) generator
1-3. Time chart of pulse stacking
3 stages for generation of 20 ps square pulse+45°
2.5 pstime

1/2 waveplate
10 ps

1st Stage:

SP
+45°

-45°

1/2 waveplate

S5 ps

2nd Stage:

S

5 ps
P+45°

S-45°

P+45°

-45°

P1/2 waveplate
2.5 ps

3rd Stage:S

2.5 psPS

2.5 psPS

2.5 psPSP

1. Macro-pulse (15~20 ps) generator
1-4. Developed & commercialized UV-Pulse Stacker~ Combining with DM, the system generates ideal 3D laser pulse ~1. Macro-pulse (15~20 ps) generator
1-5. 3D- Laser Beam Shaping system~ present status at SPring-8 ~UV- Laser source (total stability!)

Spatial Profile:

Laser Pulse Energy : 1.4% @THG

Distribution: Flattop

Pointing Stability & Reproducible
Timing Jitter < 1 ps

Deformable Mirror

Temporal Profile:
Pulse duration: 2.5 ~ 20 ps

Gaussian

UV- Pulse Stacker
Pulse duration: 2.5 ps
Pulse duration: 10 ps
Diameter：1 mm
Deformable Mirror
Pulse Stacker

Streak Image ofstacked pulses

10 ppsDeformableMirror

Flattop

Pulse Stacker (3 stages)

2. Passive micro-pulse preparation- Prism-pair UV-stretcher + Pulse Stacker

2-1. THG-Stretching system~ Combining with Pulse stacker,
it generates ideal square laser temporal pulse ~THG & UV-Stretcher (prism pair)

THG & Stretcher

240 μJ @ 266 nm

2.5 mJ @ 800 nm
X 10% efficiency=250 μJ @ 266 nm

300 μJ @ 266 nm
2 J @ 800 nm

X 50% Loss=125 μJ=>1 nC from Cathodewith 10 −5 Q.E.

Courtesy of C. Kim

2. Passive micro-pulse preparation- Prism-pair UV-stretcher + Pulse Stacker

2-2. Prism-Pair Dispersion

Courtesy of C. Kim

2. Passive micro-pulse preparation- Prism-pair UV-stretcher + Pulse Stacker

2-3. UV-Stretcher (Prism-Pair)
400 nm

800 nm

266 nmStretched
266 nmX-tal

THG
Residual 800 nm

Courtesy of C. Kim

2. Passive micro-pulse preparation- Prism-pair UV-stretcher + Pulse Stacker

2-4. UV-pulse measurement (Cross Correlator)
Correlator
X-tal

266nm <10ps
Input pulse
800nm, <100fs
1kHzDetector

UV pulsestretcher

THG (3w)

400nm DFG
Cross correlation

800nm, <150fs
Residual 800nm

111−=
266 800 400

Optical delay
Slow scan

DFG intensity
δtStretched 266nm

800nm

Optical delay
Optical delay

δt measurement -> UV 266nm pulsewidth calculation

Courtesy of C. Kim

2. Passive micro-pulse preparation- Prism-pair UV-stretcher + Pulse Stacker

2-5. UV-pulse duration (with Cross Correlator)
Correlator

Up to 6 ps, it possible
to shape nicely.

Input UV-laser
Should be perfectly
collimated to prism-pair.

Courtesy of C. Kim

3. Adaptive micro-pulse preparation- UV- & IR-DAZZLER feedback sys.+ Pulse Stacker
3-1. Candidates of SLM for UV-Laser pulse shaping
3-1-1. DAZZLER (Acousto-optics)
Simultaneously and independently performing
both spectral Phase & Amplitude of ultrafast
laser pulses. (FASTLITE)

3-1-2. Fused-silica based SLM
BimorphPiezo actuatorUtilizing silica plates◆

Directly shaping for UV-Laser◆ Higher Laser power threshold◆ Possible to shape ~ms pulse train~ However long-term drifting (At present status,very sensitive to temperature fluctuation) ~Silica plate
holder
Axis
Reflector
Laser light~ Computer-controllable silica plates complex ~Simulated Annealing Algorisms (SA)Silica plate

Compared with other type SLM
Maker nameCyber Laser Inc.

CRI

Meadlark

Jenoptik

Hamamatsu

FASTLITE

Product name

SP8 test SLM

SLM-128

SSP -256 - λ

SLM640/12

X8267

T-UV200-300

wavelength

200 nm～ limitedby gratings & optics

400 nm～

400 nm～

400 nm～

350 nm～200~300nm

transparency

99%

94%

90%

95%

90% (Reflective)

50%

Total efficiency(0.1 nm/pixel)

Damagethreshold for
amplifiedpulses (10 Hz)
Operatingspeed
Pixel number
others

20% in IR~ 40% in IR~ 70% in IR~ 70% in IR~ 70% in IR

depends on input
bandwidth (20 nm)

depends on input
bandwidth (20 nm)

input bandwidth(< 26nm)input bandwidth(< 64 nm)input bandwidth(< 100 nm)

depends on shaping

1TW/cm2(100mJ/pulse)

500MW/cm2(50μJ/ pulse)

500MW/cm2(50μJ/ pulse)

2 GW/cm2(100μJ/ pulse)

2GW/cm2(200μJ/ pulse)

1GW/cm2(100μJ/ pulse)

50ms

100 ｍs

100 ｍs

100 ｍs

500 ｍs0.04ms48

1282566401024

None (No deadspace)

Whole systemis packaged

Only SLM

Only SLM

Only SLM

Only SLM

Whole systemis packaged

Electricaladdressedtype

AOPDF type

Fused silica type:Mechanical control

Liquid crystal type30-50% in UVPrinciple of Acousto Optic (AO) ~ DAZZLER ~TeO2 crystal
Acoustic wave
Input optical beam
1°Reflection on
the input face

3.6°

14°
transducer
Reflection on
the output face

Directbeam

Diffracted
beam

Adaptation
circuitry

SMA plug

V (θ ) cos2 θoα = = Δn. a .
c cos(θ −θ )νo af

D.Kaplan and P.Tournois

J.Phys.IV France 12 (2002) Pr5-69

Principle of AO Programmable Dispersive
Filter: DAZZLER
Courtesy of Fastlite
Eout (t ) ∝ S (t / α ) ⊗ Ein (t ) où α =f ac≈ 10 −7 ⇒ Eout (ω ) ∝ S (αω ) Ein (ω )f optTransmitted pulse equals convolution ofinput pulse and acoustic wave:-single crystal design (few cm3)-quantitative shaping in phaseand amplitude-up to few ps shaping ability.
-several wavelength available(from IR to UV)Example of 4ps square pulse
made with UV DAZZLER

But Damage threshold problem In the UV!

3. Adaptive micro-pulse preparation- UV- & IR-DAZZLER feedback sys.+ Pulse Stacker
3-2. Difficulty of UV-Laser pulse measurements
3-2-1. Streak camera (Hamamatsu fesca-200)
In IR temporal resolution of 200 fs,
but…..
◆◆

Temporal resolution of 700 fs in UV
Possible to measure up to 800 ps

3-2-2. FROG or SPIDER
Possible to measure just in IR (normally, <5 ps)

FROG: 0.05 nm
500 fs -20ps◆Specially ordered FROG for 20 ps◆ UV-Dazzler as FROG or SPIDERPHAZZLER (normally, <5 ps) can be one
solution for micro-pulse measurement!

FROG: 0.3nm
200 fs -2ps

3. Adaptive micro-pulse preparation- UV- & IR-DAZZLER feedback sys.+ Pulse Stacker
3-3. Combination with DAZZLER shaping in IR,and UV pulse measurement with feedback loop.
Oscillator
DazzlerStretcher

AmplifierCompressor

THGPulse stacker

UV PHAZZLER

Courtesy of Fastlite3. Adaptive micro-pulse preparation
3-4. Features of PHAZZLER MEASUREMENTS• Design based on a single beam geometry– Exceptional stability, reproducible results, user
independent– Extreme ease of use ( no calibration, verystraightforward alignment procedure)• FROG, SPIDER, AUTOCORRELATION within the same
instrument by simply flipping a computer switch– Single shot, non iterative spectral phase and amplitude
characterization with the SPIDER method– FROG ( Intensimetric and Interferometric available)
traces for complex pulse shapes (multiple pulses,large Time Bandwidth products)– Interferometric AutoCorrelation and Intensimetric
Autocorrelation available• Tunable wavelength range

3. Adaptive micro-pulse preparation- UV- & IR-DAZZLER feedback sys.+ Pulse Stacker
3-4-1. Conventional AUTOCORRELATOR & SHG－FROG
Replace Detector to Spectrometer for FROGAUTOCORRELATOR

http://www.physics.gatech.edu/
gcuo/images/others/
AC_fig01.gif ; FROG_fig05.gif

SHGSHG-FROG

3. Adaptive micro-pulse preparation- UV- & IR-DAZZLER feedback sys.+ Pulse Stacker
3-4-2. BASEBAND INTERFEROMETRIC AUTOCORRELATIONPULSE MEASUREMENTS with DAZZLER ~ PHAZZLER ~Spectrometer for FROG

Diffracted Signals
1.4

Laser
pulse

Diffracted
beam

2nd replica
τAOPDFt0

τ variabledelay

Two-photon
detector

00.25 π0.5 π0.75 ππ1.25 π1.5 π1.75 π1.2

T w o -P h o to n S ig n a l (V )1st replica

10.8
0.6
0.4
0.2
0-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600 700 800
Time (fsec)

Courtesy of Fastlite

3-4-3. SPIDER as a perfect pulse characterization~ Conventional SPIDER CONFIGRATION ~Courtesy of N.H. Matlis
Department of Physics
University of Texas*Based on work by C. Iaconis & I.A. Walmsley (Opt.Let. /Vol. 23 No.10/May 15 1998)

3-4-4. SPIDER for characterization of macro-pulse(stacked pulse train) & micro-pulse (SP8-future plan)~ Measuring the spectral phase: Conventional SPIDER~
Modified presentation of Walmsley group, Oxford

Spectral Interferogram

790 nmFeed backing with SPIDER,,
Pulse stacking can be
optimized!

395 nm263 nmInterference term

3. Adaptive micro-pulse preparation- UV- & IR-DAZZLER feedback sys.+ Pulse Stacker
3-4-5. TIME DOMAIN SPIDER MEASUREMENTS withDAZZLER~ PHAZZLER ~Diffracted Signals

124

Diffractedbeam

τ

10Spectrometer

AOPDFt0τ variable
delay

3Intensity (AU)

Laserpulse

2nd replica

862
4

2

1

Quasi-monochromatic pulse
ς1 generated at t0
ς2= ς1+δς generated at t0+δtPhase (Rad)

1st replica

00
365

370

375

380-2
385

Frequency (THz)

A.Monmayrant et al. Optics Letters, 28, 4, p278-280 (Feb. 15, 2003)

4. Summary for generation of 15~20-ps
UV- Square laser pulse- Pulse Stacker (Macro-pulse) + Micro-pulse preparation• 15~20-ps temporal shaping with pulse stacking could
generate Square pulse!! Its flatness of the plateau
depends on optimization of micro pulses!!

• Preparation & Characterization of micro-pulse (2~5 ps)
It’s very fine to shape : You have to exactly measure
the shape of aimed laser pulse.
– Grating compressor: It’s characterized by SPIDER (SP8).
– Prism-pair: It’s characterized by Cross Correlator (PAL).
– Adaptive DAZZLER(AO): It’s characterized by itself (Fastlite).

• For 3D-laser pulse shaping, the complex system withadaptive DAZZLER & adaptive Deformable Mirror
might have a lot of possibilities with fine tuning.

• For arbitrary 3D-laser pulse shaping, the complex systemwith adaptive Silica-SLM & adaptive DM should be thegoal for any case. Especially, It can be utilized for multibunch beam shaping.
A) Computer-aided Silica-SLM (Spatial Light Modulator)
Rectangular Pulse shaping (Arbitrary Shape)B) Computer-aided DM (Deformable mirror)
Flattop spatial profile (Arbitrary Shape)
SLM

DM

Automatic Control Optics• Spatial shaping (DM)• Pulse shaping (SLM)• Wave front Control (DM))))
2 ~ 12 ps Fundamental
2 ~ 5 ps THG (263 nm)