1. High energy, high repetition rate pump laser system for OPCPAs A.-L. Calendron 1,2,3, L. E. Zapata 1,4, H. Çankaya 1,2, H. Lin 4 and F. X. Kärtner 1,2,3,4 1 Center for Free-Electron Laser Science, DESY, Hamburg, Germany 2 The Hamburg Centre for Ultrafast Imaging 3 Physics Department, University of Hamburg 4 Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, MIT, Cambridge, MA, USA 26. August 2014

2. Why is high energy needed ? E 1,  1 E 2,  2 E 3,  3 E 4,  4 E 5,  5 E 6,  6 E 7,  7 E 8,  8 Waveform Nonlinear Optics: study and control of strong-field light-matter interactions in atoms, molecules and solids on a sub-cycle time scale multi-mJ IR pulses for phase-matched long-wavelength HHG Parallel synthesis Ti:Sapphire frequency syntheziser: Results Cirmi et al., LPHYS (2014) Rossi et al., CLEO (2014)

3. Pump chain for OPCPA pumping Cryo- Yb:YAG Amplifier 60 mJ 0.6 nm, 0.4 ns 1 kHz Cryo- Yb:YAG amplifier 1.1 J 0.7 nm, 0.8 ns 1 kHz Yb Master Osc. 1 nJ 200 fs duration 42.5 MHz Yb:KYW Regen > 5 mJ 3 nm, 2 ns 1 kHz MLD grating Compressor ~ 1 J 10 ps, 1 kHz CFBG Stretcher 0.6 nJ 10 nm stretched (0.65 ns/n m) MLD grating Compresso r 4.2 mJ, 700 fs, 1 kHz CEP Stable front-end ~10 nJ, 570 nm- 2.5 µm, 1 kHz OPCPA +Frequency Synthesis ~ mJ, TL: <3 fs, 1 kHz

4. Pump chain for OPCPA pumping Cryo- Yb:YAG Amplifier 60 mJ 0.6 nm, 0.4 ns 1 kHz Cryo- Yb:YAG amplifier 1.1 J 0.7 nm, 0.8 ns 1 kHz Yb Master Osc. 1 nJ 200 fs duration 42.5 MHz Yb:KYW Regen > 5 mJ 3 nm, 2 ns 1 kHz MLD grating Compressor ~ 1 J 10 ps, 1 kHz CFBG Stretcher 0.6 nJ 10 nm stretched (0.65 ns/n m) MLD grating Compresso r 4.2 mJ, 700 fs, 1 kHz CEP Stable front-end ~10 nJ, 570 nm- 2.5 µm, 1 kHz OPCPA +Frequency Synthesis ~ mJ, TL: <3 fs, 1 kHz

5. Experimental setup E out LD M3M2 M1 DC XTAL LL λ/2 M7 M6 λ/4PCTFP M5 M4 LPB S S Regenerative amp. FI Osc E seed E osc CFBG1 FA1 CFBG2 FA2 CFBG3CFBG4 C2 C1 C3 Stretcher λ/2 TFP M8 FM1 &2 RM G1 G2 Compressor To cryo-multi- pass amp. To Front- end Yb:KYW – 42.5 MHz 210 fs, nJ CFBG + 2 YDGA 0.6x ns/nm nm bandwidth Eout = 0.6 nJ Dual crystal Yb:KYW 1 kHz Multi-layer dielectric grating Double pass

6. Regenerative amplifier Calendron et al., Opt. Expr. (submitted) -E out = 6.4 mJ @ 1 kHz, from 0.6 nJ seed Long term stability Caustic: M 2 < 1.1 Comparison with simulations

7. Pump chain for OPCPA pumping Cryo- Yb:YAG Amplifier 60 mJ 0.6 nm, 0.4 ns 1 kHz Cryo- Yb:YAG amplifier 1.1 J 0.7 nm, 0.8 ns 1 kHz Yb Master Osc. 1 nJ 200 fs duration 42.5 MHz Yb:KYW Regen > 5 mJ 3 nm, 2 ns 1 kHz MLD grating Compressor ~ 1 J 10 ps, 1 kHz CFBG Stretcher 0.6 nJ 10 nm stretched (0.65 ns/n m) MLD grating Compresso r 4.2 mJ, 700 fs, 1 kHz CEP Stable front-end ~10 nJ, 570 nm- 2.5 µm, 1 kHz OPCPA +Frequency Synthesis ~ mJ, TL: <3 fs, 1 kHz

8. Gain narrowing and compression -Stretching ratio: 0.65 ns/nm -Compression of the 3.6 nm broad spectrum to <700 fs -Energy in the pedestals: 16%

9. Pump chain for OPCPA pumping Cryo- Yb:YAG Amplifier 60 mJ 0.6 nm, 0.4 ns 1 kHz Cryo- Yb:YAG amplifier 1.1 J 0.7 nm, 0.8 ns 1 kHz Yb Master Osc. 1 nJ 200 fs duration 42.5 MHz Yb:KYW Regen > 5 mJ 3 nm, 2 ns 1 kHz MLD grating Compressor ~ 1 J 10 ps, 1 kHz CFBG Stretcher 0.6 nJ 10 nm stretched (0.65 ns/n m) MLD grating Compresso r 4.2 mJ, 700 fs, 1 kHz CEP Stable front-end ~10 nJ, 570 nm- 2.5 µm, 1 kHz OPCPA +Frequency Synthesis ~ mJ, TL: <3 fs, 1 kHz

10. White-light generation Regen Comp TFPλ/2 L1 X1 X2 X3 X4 TFPλ/2 TFP L2 L3 L5 Spect. X5 M1M1 M6M6 M2M2 C1 M3M3 C2 M4M4 C4 D1 M5M5 C3 PM L6 M7M7 BS White-Light 1 OPA 1 OPA 2 White-Light 2 f-2f L4

11. Pump chain for OPCPA pumping Cryo- Yb:YAG Amplifier 60 mJ 0.6 nm, 0.4 ns 1 kHz Cryo- Yb:YAG amplifier 1.1 J 0.7 nm, 0.8 ns 1 kHz Yb Master Osc. 1 nJ 200 fs duration 42.5 MHz Yb:KYW Regen > 5 mJ 3 nm, 2 ns 1 kHz MLD grating Compressor ~ 1 J 10 ps, 1 kHz CFBG Stretcher 0.6 nJ 10 nm stretched (0.65 ns/n m) MLD grating Compresso r 4.2 mJ, 700 fs, 1 kHz CEP Stable front-end ~10 nJ, 570 nm- 2.5 µm, 1 kHz OPCPA +Frequency Synthesis ~ mJ, TL: <3 fs, 1 kHz

12. Cryogenic Yb:YAG amplifier: Gain Composite disk with fashioned edges Control disk Zapata et al., ASSL 2013, talk AF3A.10 Zapata et al., Opt. Lett. (submitted) Out  Spatial filter Cryogenic CTD Heat Laser Fluorescence THE PREDICTED INCREASE IN GAIN HOLD-OFF WAS REALIZED

13. Chirped pulse amplification 13 68 mJ pulse energy Maximum intensity ~ 10 GW/cm 2 The output was stable at all rep. rates 28% slope eff. Pulse energy [mJ] Absorbed energy [mJ]  Franz-Nodvik calc. verifed gain/loss measurements Frantz-Nodvik T = 93% G = 3.3x ~ 5.2 dB Frantz-Nodvik T = 93% G = 3.3x ~ 5.2 dB

14. Results with optimized seed laser Limitations in seed energy and stretching overcome now with the new seed: E seed = 5.5 mJ and τ = 2.35 ns With only 6 passes, >30mJ extracted from the disk, compared to 23 mJ with limited seed. Output energy for 6 passes through the disk:

15. Summary Demonstration of a high energy pump-line for OPCPA pumping Yb doped laser systems => scalability to high energies – Suitable for pumping OPCPA´s up to high energies Outlook: – Compression of the high energy pulses – Parametric amplification of the front-end

16. Thank you for your attention !

17. Backups

18. Simulations: differential equations Evolution of the population inversion: Evolution of the pump fluence through the crystal: Evolution of the laser fluence through the crystals: Evolution of the laser fluence through the cavity: With: and:

19. Simulations

20. Yb:KYW: CW characterization 19.4 W 1031 nm Cavity dumped:

21. Pointing stability: after compressor

22. Cryo Yb:YAG: Bandwidth measurements Fluorescence bandwidth measured for different temperatures by adjusting the heat load on the cold head

23. Cryo Yb:YAG: Bandwidth measurements Spectral bandwidth for different pump power:

24. Summary Demonstration of a high energy pump-line for OPCPA pumping – Stretcher: CFBG, S-R = 0.65 ns /nm – Regenerative amplifier: Yb:KYW, dual crystal cavity E max = 6.5 mJ @ 1 kHz τ = 700 fs after compression with MLD gratings – Power amplifier: Cryogenic Yb:YAG composite thin-disk 6 passes: 30 mJ – 12 passes: 64 mJ Outlook: – 100 mJ after the power amplifier – Compression of the high energy pulses – Parametric amplification of the front-end