Ultrawideband regenerative amplifiers via intracavity acousto-optic programmable gain control

Transcription

1 Ultrawideband regenerative amplifiers via intracavity acousto-optic programmable gain control Thomas Oksenhendler, Nicolas Forget, Daniel Kaplan, Pierre Tournois Fastlite, Bât 403, Ecole Polytechnique, Palaiseau, France Pierre-Mary Paul, Gregory M. Greetham, Frederic Estable Amplitude Technologies, 2, rue du Bois Chaland, EVRY, France

2 Ultrawideband regenerative amplifiers Goals : regenerative amplifier with : sub-20fs pulses at 800 nm, mj-level, high temporal pulse contrast. Problems : gain narrowing => spectrum FWHM < 35nm reliability, pre/post pulses, ASE, stability.

3 Ultrawideband regenerative amplifiers Regenerative amplification Input spectrum Output spectrum Polarizer Pockels cell Ti:Sa Spectral gain Spectral gain narrowing laser amplification Transmission/reflectivity of intracavity elements pass 1 pass 2 pass N

4 Ultrawideband regenerative amplifiers Spectral gain narrowing => spectrum FWHM < 35nm Solution : Regenerative pulse shaping 1,2 Spectral filter Optical elements Laser spectral gain Transmission Transmission Transmission Global transmission λ x x = λ λ flat spectral gain λ 1 C.P.J. Barty, G.Korn, F.Raski, C.Rose-Petruck, J.Squier,A.C.Tien, K.R.Wilson, Y.V.Yakovlev, K.Yamakawa, Regenerative pulse shaping and amplification of ultrabroadband optical pulses, Opt.Lett. Vol.21, No.3, pp (1996) 2 C.P.J. Barty, T.Guo, C.LeBlanc, F.Raski, C.Rose-Petruck, J.Squier, K.R.Wilson, Y.V.Yakovlev, K.Yamakawa, Generation of 18-fs multiterawatt pulses by regenerative pulse shaping and chirped-pulse amplification, Opt.Lett. Vol.21, No.9, pp (1996)

5 Ultrawideband regenerative amplifiers Spectral filter Regenerative pulse shaping Thin etalon Spectral mask Birefringent filter Multiple dielectric layers Drawbacks: pulse replica, cavity instability, lack of programmability

6 Ultrawideband regenerative amplifiers Regenerative pulse shaping Spectral filter Acousto-Optic Programmable Gain Control Filter (AOPGCF) acoustic wave non-diffracted beam diffracted beam - similar to AOPDF uses non diffracted beam - Brewster incidence angle low passive losses - collinear interaction geometry efficiency and resolution - very easy calibration crystal physical constants and 1 spectral point

7 Acousto-Optic Programmable Gain Control Filter Advantages : low residual losses, high spectral resolution (1nm) no spurious pulses, complete software programmability, easy installation and calibration Drawbacks : low damage energy threshold : 1mJ/1mm 2, dispersion of the TeO2 crystal : => > fs 3 to compensate Acousto-Optic Programmable Dispersive Filter (AOPDF)

8 Experimental setup Oscillator Stretcher AOPDF regen with AOPGCF Öffner type with grating 1200mm -1 (110nm bandwidth) Dazzler HR800 Fastlite (phase control) Compressor Spectrometer Photodiode + oscilloscope High dynamic third order cross-correlator SPIDER HR4000, Ocean optics Tektronix Sequoia, Amplitude Technologies APE, 20-80fs

9 Ultrawideband amplification experimental results Spectrum enlargement : 1 w AOPGFC (80 nm) Intensity (a.u.) w/o AOPGFC (35 nm) Wavelength nm

10 Ultrawideband amplification experimental results Temporal profile : 1 Intensity (a.u w AOPGFC (18 fs) w/o AOPGFC (29 fs) 1.01 x FT limit 1.02 x FT limit Time (fs)

11 Ultrawideband amplification experimental results Pulse contrast : 1.E+00 1.E-01 Intensity (a.u 1.E-02 1.E-03 1.E-04 1.E-05 w/o AOPGFC w AOPGFC 1.E-06 1.E-07 1.E Delay (ps)

12 Conclusions Summary : spectral enlargement from 35nm to 80nm shorter pulses duration 29fs to 18fs FWHM no ASE-contrast degradation (10 7 ) high contrast stability of 18fs pulses is 1.2%rms reliability energy limitation to about 0.5 mj [without post amplification] 200 TW laser chain system

13 200 TW laser system Normalized Intensity (a.u.) E-3 1E-4 1E-5 1E-6 1E-7 1E-8 1E-9 1E-10 1E-11 1E-12 1E-13 1E-14 1E-15 Temporal pulse contrast Time Delay (ps) Intensity (a.u.) Wavelength (nm) Time amplitude and spectral phase >5 J 23 fs Time (fs) 8 Spectral Phase (Rad)