Techniques de mesure et de stabilisation des Amplificateurs CEP Ti:S. J F. Hergott, O. Tcherbakoff, CEA/DSM/IRAMIS/SPAM/SLIC

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1 Techniques de mesure et de stabilisation des Amplificateurs CEP Ti:S J F. Hergott, O. Tcherbakoff, CEA/DSM/IRAMIS/SPAM/SLIC / / /

2 CEP stabilized Ti:S laser: different steps or le oscillato CEP stabl Step 1: Synergy Pro + Verdi V6 D. J. Jones, et al. Science 288, 635 (2000). A. Polonski, et al. PRL 85, 740 (2000). Phase Stabilization is processed by Menlo XPS800 CEP in loop error signal RMS noise ~80 150mrad Step 2: high ratio grating based stretcher/compressor ultra stable mounts to reduce vibrations sensitivity Stretcher < 300ps 5ps/nm Step 3: reducing vibration sources due to cooling systems (pump lasers_cryohead ) Step 4: shot to shot khz rep rate for efficient slow feedback loop for CEP control compressor E. Gagnon, et al. OL. 31, 1866 (2006). C. Li, et al. OE 14, (2006). A. Baltuška, et al. Nature 421, 611 (2003). T. Fordell, et al. OE 17, (2009). L. Canova et al. OL 34,, 1333 (2009). S.Chen, et al. App. O. 48, 5692 (2009). M. Kakehata, et al., OL 26, 1436 (2001) M. Kakehata, et al. OE 12, 2070 (2004). M. Takeda, et al., JOSA 72, 156 (1982)

3 CEP stabilized laser scheme oop Slow fe eedback l Fast feedback loop Oscillator Synergy XPS 3.4 m CEP stretcher Element dispersif Regen amplifier 4 pass amplifier APS 800 compressor 3 4W output f 2f CEA 4 pass Cryogenic Amplifier 6 20W 1.5 m EO Slow feedback loop E. Gagnon, et al. OL. 31, 1866 (2006). M. Kakehata, et al., OL 26, 1436 (2001) C. Li, et al. OE 14, (2006). T. Fordell, et al. OE 17, (2009). f divider Genpulse Pu ump 20W Pu ump 20W Pu ump 20W Pump 30 0W

4 CEP measurement: spectral interferometry successive e shots Δω τ Spectrometer (slit imaging) ω Techniques de mesures de la dérive de CEP Δϕ 0 Δϕ 0 Beam splitter Fixed mirror Dephasing object Laser large spectrum (short pulse duration) Moving mirror Time delay τ Between two pulses Not self referenced technique (1 arm is the reference) f f q ( f ) Stability problems when dephasing object is a laser chain

5 CEP measurement: f to 2f interferometry Based on Mach Zehnder ou colinear interferometer (Kakehata et al. 26 OL (2001)) Different steps: 1 White Light generation filament has to be stable (σ laser < 1% RMS) & spectrum large enough 2 interference between high frequences & doubled low frequences of the WL fundamental spectrum Issu de Baltuska et al. IEEE Journal of selected Topics in Quantum Elec. 3 shot to shot acquisition and treatment I ( ω ) I ( ω ) + I ( ω ) F SH ( 0 ) + 2 I ( ω) I ( ω) cos ω. Δ τ + θ + ϕ F SH shift frequency 1µm frequency shift and superimposition Spectral fringes Spectral fringes Fringe position at ϕ 0

6 Treatment for CEP determination Takeda et al. JOSA 72 (1982) Dorrer et al. JOSA B 15&16 (1998&1999) FTSI Algorithm (Fourier Transform spectral interferometry) I(ω) ( ) ( ) ( ) 1) Spectral I ω IF ω + ISH ω fringes + 2 I ( ω) I ( ω) cos ω. Δ τ + θ + ϕ ( ϕ 0 ) F SH shift ω TF 2) Temporal domain TF(I(ω)) filtering TF 1 filter 3) Temporal shift τ 0 τ ωτ ϕ ϕ 0 ω ψ ω CEP drift by shot to shot FTSI treatment Su uccessive las ser shots Ψ = ϕ ( ω ) ωτ 0 (

7 MC: focusing mirror M: plane mirror Ag L: lens fto 2f experimental set up Spectrometer f=300mm 3 gratings: grooves/mm Acquisition Signal processing MC R=1m M5 L2 multi khz acquisition M1 M2 polariser BBO e=300µm Focused IR M4 Calcium fluoride or Sapphire plate e=2mm Diagnostic i experimental setup White light CEP drift measurement NO absolute CEP value MC R=0,25m M3 L1

8 Carrier Envelope Phase drift CEP related to the position of the oscillating field in the temporal envelop of the pulse. Non fixed position group velocity phase velocity (Δn=n g n 0) (dispersion) Δφ 0 Δφ Δφ 0 2Δφ E(t) T rep temps Dispersive materials (optics, crystals, prisms, gratings, air etc ) induces CEP drift due to pointing, energy instabilities or vibrations Controling the dispersion (different elements) CEP drift control and correction Different ways to succeed AOM pump energy in oscillator Beam path in dispersive material Grating dispersion control Dispersive media (AOPDF, 4f SLM, EO crystal)

9 CEP stabilization in grating based lasers Electroni cs Oscillator f-2f XPS Stretcher Regen. amplifier N-pass amplifier F-2F Compressor Main amplifier (cryocooled) Grating based laser systems more sensitive to vibrations but CEP compatible Etienne Gagnon Opt. Lett.,31,1866 (2006) 1,4mK,1kHZ,>35fs Masayuki Kakehata, Opt. Express 12,2070(2004) 3,5mJ (before comrpession),1khz,50fs Slow CEP drift has to be corrected for grating based systems or not

10 CEP slowloop on oscillator 1/2 Electroni cs Δφ 0 Oscillator f-2f XPS Stretcher Regen. amplifier N-pass amplifier Slow feedback loop F-2F Δφ 0 Compressor Main amplifier (cryocooled) Δφ 0 Oscillator pump power modulation by AOM/EOM Small pump energy variation converted in CEP shift (Kerr shift n = n linear + n 2.I) Same effect as for fast loop secondary slow loop A. Poppe et al., App. Phys B 72, 373 (2001)

11 CEP slowloop on oscillator 2/2 A. Baltuska, Nature 421, 611 (2003) 1mJ,1kHZ,20fs1kHZ Not grating based g systems Low stretching factor (bulk) Femtolasers Gmbh (CLEO Munich 2011) Up to 5mJ,1kHZ,20fs Transmisssion gratings compression Phase noise 195mrad RMS 2mJ,1kHZ,35fs, CEP Noise 350mrad single shot 220mrad 10ms average (Hergott et al. CLEO Munich 2011) grating based systems High stretching Slow correction ~few Hz T. Imran, Opt. Express, 15,104 (2006) 4,2mJ,1kHZ,25fs, CEP Noise 180mrad 20ms average T. Fordell, Opt. Express 17, (2009) 6mJ,1kHZ,30fs, CEP Noise 490mrad single shot

12 CEP slowloop with wedges Electroni cs Δφ 0 Oscillator f-2f XPS Prismes /wedges pair Stretche r Regen. amplifier N-pass amplifier Slow feedback loop F-2F Δφ 0 Compressor Main amplifier (cryocooled) Δφ 0 Not grating based systems Low stretching factor (bulk) Transmisssion gratings compression Efficiency: 160mrad/mm (for chosen materials) Phase noise 195mrad RMS Up to 5mJ,1kHZ,20fs C. Grebing et al.appl. Phys. B 97(3), ( 575 (2009) Femtolasers Gmbh (CLEO Munich 2011)

13 Stretcher/compressor effect on CEP 1/3 C. Li, Opt. Lett. 31, 3113 (2006) C. Li, Appl. Phys. Lett. 92, (2008) Grating Strecher Grating Compressor Beam pointing instability R2 ϕ CE θ d θ i Θi=65 G=470cm 1500t/mm R1 ϕ CE Z. Chang, Appl. Opt. 45, 8350 (2006) Stretcher & compressor are in 2 pass configuration => CEP drift due to 1st pass compensated by 2 nd pass => low CEP noise induced ±60µrad => 100mrad CEP noise BUT.

14 CEP slowloop on stretcher/compressor grating Electroni cs Δφ 0 Oscillator f-2f XPS Stretcher Regen. amplifier N-pass amplifier Slow feedback loop F-2F Δφ 0 Compressor Main amplifier (cryocooled) Δφ 0 Stretcher & compressor are in 2 pass configuration => CEP drift due to 1st pass compensated by 2 nd pass => low CEP noise induced ±60µrad => 100mrad CEP noise BUT. Gratings can be used to apply a CEP correction slow loop

15 Slow loop grating angle Angle variation slow loop R2 ϕ CE θ d θ i R1 ϕ CE Z. Chang, Appl. Opt. 45, 8350 (2006) 0, deg 300mrad CEP shift (corresponds to 1, µrad pointing instability) Big correction range Drawback: not very fast t(technique applied on Coherent tinc. Systems), vibrations if too fast

16 Slow loopgratings separation Grating separation slow loop R ϕ CE CEP shift (rad) θ d θ i -2 R1 ϕ CE -8 Z. Chang, Appl. Opt. 45, 8350 (2006) 2,5mJ,1kHZ,25fs, 2mJ,1kHZ,27fs, CEP CEP single average shotover 320mrad 50ms C. Li, Opt. Exp. 14, KMLabs 11468(2006) Inc ΔG (nm) 100nm movement 300mrad CEP shift with big correction range Drawback: not very fast (15Hz), vibrations if too fast

17 AOPDF slow loop Electroni cs Δφ 0 Oscillator f-2f XPS Stretche r AOPDF Regen. amplifier N-pass amplifier Slow feedback loop F-2F Δφ 0 Compressor Main amplifier (cryocooled) Δφ 0 DAZZLER ϕ acc relative timing between acoustic carrier and envelope Is controlled CEP can be controlled to a fixed value (See N. Forget talk) 2mJ,1kHZ,25fs Loop < 15 HZ 6mJ,1kHZ,30fs Loop < 6 HZ 130 mrad10 shots average? N. Forget, Opt. Lett. 34, 3647 (2009) 510 mrad single shot T. Fordell, Opt. Express 17, (2009)

18 4f line SLM slow loop Instead of DAZZLER use of an adaptive phase modulator: grating based 0 dispersion 4fsystem M. Kakehata, CLEO 2005 H. Wang et al., Appl Phys. B 98, 291 (2010) 2mJ,1kHZ,30fs, CEP 50ms average Drawback: very slow vibrations in Drawback: very slow, vibrations in 4f line bad CEP correction

19 CEP slow loop by Electo Optic effect 1/2 Δφ 0 Electroni O. Gobert et al., Optics Express 19, (2011) cs Oscillator f-2f XPS Stretcher EO Regen. amplifier N-pass amplifier Slow feedback loop Δφ 0 HV Δφ 0 F-2F Compressor Main amplifier (cryocooled) 8 7 Phase shift (radian) d LiNbO3 crystal L E HV (U) O X Y Z CEP shift (rad) Linear regression Measured slope 3.5rad/kV Theoretical slope 3.1rad/kV Very good agreement between Applied voltage (V) experimental results and calculations

20 CEP control by Electo Optic effect 2/2 LiNbO3 crystal: 4cm long, 4mm thick Placed in 2 pass configuration after stretcher bigger correction range Shot to shot CEP@500Hz, 10ms 100Hz acquisition Up to 20mJ(before compression), 1kHZ, 35fs teo loop Withou loop Time (min) With EO σ=440mrad shot to shot and 250mrad 10ms averaged with loop σ 100Hz shot and to 60Hz shot and No remaining 120mrad 10ms jumps averaged with Higher noise due to lower energy stability? Or small vibrations of the head? 100Hz and 60Hz No remaining jumps Moon et al. Laser & Photon. Rev 4, 160 (2010)

21 CONCLUSION f 2f CEP measurements: no absolute value but relative drift Simple to use but energy fluctuation dependent (absolute measurements based on physical process like stereo ATI, HHG complicated) f 2f detection can be very fast (all analogical), the faster the CEP measurement the faster the correction important for high rep rate laser (>1kHz) Shot to shot meausrement are important average values just give an idea Different techniques enable CEP correction in amplified systems (AOPDF and EOCEP device promising i for highh rep rate CEP correction) it is better to have a slow loop independent from oscillator for long term stability The better the oscillator is stabilized the better the ampliedpulseswill be even The better the oscillator is stabilized the better the amplied pulses will be, even with large stretching ratio systems

22 THANK YOU FOR YOUR ATTENTION!

23 Electo Optic effect Some details on the calculation: group velocity phase velocity (Δn=n g n 0) (dispersion) g => Difference between group delay and time delay Difference between group delay and time delay with & without HV field applied ΔL= d 32 EL, d 32 is the piezoelectric constant (size increase of the crystal) & is 50 times lower than r 33 electro optic coefficient => negligible

24 Pointing instability in bulk material Some details on the calculation: group velocity phase velocity (Δn=n g n 0) (dispersion) g => Difference between group delay and time delay Pointing instability of 20µrad 100µrad CEP shift due to additional path in a 10 mm thick plate at 1 incidence and 1mrad for 7 incidence Very low incidence in bulk material Can become significative for brewster angle window pair 10mmthick and 4passes Can become significative for brewster angle window pair 10mm thick and 4passes (cryo cooler) with a 60µrad pointing stability mrad