s. karsch-the petawatt field synthesizer – current status and recent progress
TRANSCRIPT
The
Petawatt Field Synthesizer
Current status and recent progress
Laboratory for Attosecond and High-Field PhysicsMax-Planck-Institut für Quantenoptik
Garching, Germany&
Ludwig-Maximilians-Universität München, Garching
ELI-BEAMLINES SCIENTIFIC CHALLENGES WORKSHOP, PragueApril 26-27, 2010
Stefan Karsch
Dienstag, 27. April 2010
Coworkers
current:
I. Ahmad, S. Klingebiel, M. Siebold, C. Wandt, Zs. Major, S. Trushin, Ch. Skrobol, M. Mero, A. Popp, J. Irlinger, F. Krausz
former: M. Siebold, J. Hein, J. Osterhoff, J. Fülöp, S. Kruber
Dienstag, 27. April 2010
ELI Beamlines - PFS
Dienstag, 27. April 2010
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ELI beamlines facility
Dienstag, 27. April 2010
ELI Beamlines Laser
Peak intensity: 1023 W/cm2
Plasma formation threshold: 1010 W/cm2
⇒ Temporal contrast: ≈ 1013 W/cm2
Pulse shaping capabilities directly benefit from spectral bandwidth ⇒ High energy, broadband seed for power amplifiers is desirable
log(I)
time
plasma formation threshold
0
-10
-15
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Max-Planck-Institutfür Quantenoptik
Ludwig-MaximiliansUniversität München
5 fs 3 J 10 Hz
High bandwidth(OPCPA) Large crystals High – rep.
pump
Yb:YAG CPA pump laserLarge aperture DKDP OPCPAbulk/chirped mirror compression
Diode pumpingThin KDP or DKDP
CPAHigh pump intensityps pulse duration
MPQ project PFS: Strategy
Dienstag, 27. April 2010
Basic concept and layout
Dienstag, 27. April 2010
OPCPA design
~20 J, 1-2 ps @ 515 nmfrom pumplaser
in several beams
ultrabroadband seedfrom frontend
700 nm – 1400 nm
Dienstag, 27. April 2010
Zs. Major et al., Review of Laser Engineering, 37, 431 (2009)
OPCPA design
• Large aperture DKDP crystals Lozhkarev et al. Laser Phys. Lett. 4, 421 (2007)
• Total pump energy: 20 J @ 515 nm• 1D modelling with saturation (pump depletion)• no dispersion included
stage pump energy
ampl. signal energy
crystal length
1 2.5 mJ 500 µJ 3.8 mm
2 20 mJ 3.5 mJ 3.8 mm
3 200 mJ 40 mJ 3.5 mm
4 1 J 169 mJ 3.0 mm
5 3 J 722 mJ 2.8 mm
6 5 J 1.7 J 2.4 mm
7 5 J 2.8 J 1.7 mm
8 5 J 3.8 J 1.5 mm
Dienstag, 27. April 2010
frontend
1. CPA pump laser seed: - 30 % of oscillator output- soliton self-frequency shift in a photonic crystal fiber to 1030 nm C.Y. Teisset et al., Opt. Exp. 13, 6550 (2005)- Yb:Glass fiber amplifier: 1W at 70 MHz (14 nJ)
21
2. OPA chain seed: - 70 % of oscillator output – stretched – amplified- compressed- cascaded hollow-core fiber (HCF) scheme for spectral broadeningAhmad et al., Appl. Phys. B, in press (2009)
Dienstag, 27. April 2010
frontend• Ti:Sa oscillator • Ti:Sa 10-pass (modified Femtopower CompactPro): up to 2 mJ, 60 nm, 1 kHz• prism compressor: ~23 fs
spectral shifting for pumplaser seed
broadband seed generation
Dienstag, 27. April 2010
frontend
2
1
50 µJ in the range of 700 – 1400 nm
Dienstag, 27. April 2010
26 HD mirrors (1” dia.) , 2-pass configuration (52 reflections), ~ -500 fs2/reflection, angle of incidence: 10°, separation: 96 mm
- stretched pulse duration: 4.8 ps (FWHM)- throughput ~ 90 %- output energy 1.2 mJ- pulse duration after compressor: 19.1 fs
frontend
High-dispersive mirrors instead of prism compressor in CPA systemPervak et al., Opt. Exp. 16, 10220 (2008) Pervak et al., Opt. Exp. 17, 19204 (2009)
Dienstag, 27. April 2010
frontend
High-dispersive mirrors instead of prism compressor in CPA systemPervak et al., Opt. Exp. 16, 10220 (2008) Pervak et al., Opt. Exp. 17, 19204 (2009)
FROG-trace
hybrid compressor all-dispersive mirror compressor
Dienstag, 27. April 2010
frontend
High-dispersive mirrors instead of prism compressor in CPA systemPervak et al., Opt. Exp. 16, 10220 (2008) Pervak et al., Opt. Exp. 17, 19204 (2009)
excellent beam quality
far field near field
Dienstag, 27. April 2010
pump laser
Dienstag, 27. April 2010
pump laser
6.5 m grating separation
300 mJ, 3.5 nm, 10 Hz
Dienstag, 27. April 2010
pump laser
300 mJ, 3.5 nm, 10 Hz
Dienstag, 27. April 2010
pump laser
300 mJ, 3.5 nm, 10 Hz
Dienstag, 27. April 2010
Pumplaser
Pulse compression:
• 1.4 ± 0.3 ps• remaining higher orders resulting
in temporal wings• spectrum of ~ 3.5 nm could
support ~ 800 fs TL pulses
→ more careful alignment for cleaner compressed pulse
→ received Dazzler for fine tuning
Single-shot FROG
Dienstag, 27. April 2010
Next steps: pump laser design
New simulations of amplification in diode-pumped Yb:YAG amplifiers:• include multipass pumping scheme• wavelength dependence of pump
Dienstag, 27. April 2010
Next steps: pump laser design
2 × 240 mJ 4 × 1 J 4 × 12 J
• Yb:YAG crystals in stock• setup is under way
Dienstag, 27. April 2010
Timing jitter between pump and seed
Dienstag, 27. April 2010
- total path difference ~ 400 m- max. jitter: ~ 100 fs = 30mm- stabilization to 10-7 needed
Timing jitter between pump and seed
Dienstag, 27. April 2010
Timing jitter between pump and seed
Dienstag, 27. April 2010
Timing jitter between pump and seed
Sum frequency generation in 120 µm BBO
spectrometer
I
l
spectral gating techniqueT. Miura et al. Opt. Lett. 25, 1795-1797 (2000)
Dienstag, 27. April 2010
Timing jitter between pump and seed
Sum frequency generation in 120 µm BBO
spectrometer
I
l
- resolution depends on pulse chirp and spectral resolution of spectrometer
spectral gating techniqueT. Miura et al. Opt. Lett. 25, 1795-1797 (2000)
Dienstag, 27. April 2010
20
jitter problems I
(shot-to-shot)
Dienstag, 27. April 2010
21
how to produce annoying jitter issues® Take a vacuum pump® Connect it to an unused part of the optical table ® Hide it behind a laser protection wall® Switch it on and off from time to time...
Dienstag, 27. April 2010
jitter problems II
(shot-to-shot)
Dienstag, 27. April 2010
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active stabilization
® significantly reduced point-to-point jitter® large, but slow drift still present can be
compensated at 10 Hz
spectral acquisition = jitter
average
difference > limit?
reference shot 2 shot 3 shot 4
move delay stage by difference
Sum frequency fluctuations - inacceptable before stabilization
- now 10% fluctuation- start OPA experiments
Dienstag, 27. April 2010
24
active stabilization
stabilized
stabilized not stabilized
-stabilized with av 2, limit 100 fs - std =105 fs
Dienstag, 27. April 2010
finally: first broadband OPCPA gain
25
shot-to-shot-amplification stability 11% RMS
Gain from 750 to almost 1400 nm:However, strong modulations
due to large spectral intensity variations and over-saturation in too thick crystal.
Next experiments will use 3 mm crystal
Dienstag, 27. April 2010
26
Comparison with simulations
We seem to understand what is happening...Dienstag, 27. April 2010
26
Comparison with simulations
We seem to understand what is happening...Dienstag, 27. April 2010
26
Comparison with simulations
We seem to understand what is happening...Dienstag, 27. April 2010
Summary and next steps
• Frontend to produce optically synchronized seed pulses is complete.
• Pump laser chain: - ~100 mJ compressed to ~1.4 ps - large timing jitter from air fluctuations and mechanical instabilities can be reduced to below ~100 fs by → permanent beam tubes → automated slow drift correction - feasible design for next amplification stages to reach ~50 J
→ First OPCPA experiments show bandwidth for efficient short pulse generation
Dienstag, 27. April 2010
5 fs 1 J 1 kHz
ELI strategy
High bandwidth(OPCPA) Large crystals High – rep.
pump
Yb:YAG CPA pump laserLarge aperture KDP OPCPAbulk/chirped mirror compression
Diode pumpingThin KDP or DKDP
CPAHigh pump intensity
Dienstag, 27. April 2010
Towards ELI frontend
Schemes for upscaling the pumplaser repetition rate
• thin-disk approach: Max-Born-Institut, Berlin 100 Hz, ~300 mJ, 1.5 ps (@ several tens of mJ)
Max-Planck-Institut für Quantenoptik, Garching 3 kHz, ~30 mJ, 1.6 ps
→ limited total energy that can be extracted due to transverse lasing if disk size is too large→ CW pumping technology is expensive
• gas-cooled slab approach: e.g. Mercury project
→ higher demands on pump-beam quality for efficient pumpingDienstag, 27. April 2010
MPQ - Current System (T. Metzger)
• regenerative amplifier (CPA)• Ti:sa osc, fiber preamp. @1030nm • 25 mJ @ 3 kHz (32 mJ before comp.)• 1.6 ps pulse duration • total gain of 3 x 1010 (inc. fiber amp)• 1 nm bandwidth• 280 W Pump power (5.2 kW/cm²)• pump spot Ø 2,6 mm• round trip gain 1.2 (inc. losses)• round trip losses 6%• disk gain in V-pass 1.13• disk thickness 1/10 mm• < 0.7 % pulse-to-pulse stability (RMS)
Dienstag, 27. April 2010
Multipass in Constructionmirror holder 4-f imaging
vacuum chamber
Yb:YAG disk amplifier head
2 x 10 V-passes via the disk
Dienstag, 27. April 2010