1. Formatvorlage des Untertitelmasters durch Klicken bearbeiten 1/27/15 Passively CEP-stable front end for optical frequency synthesis 1 Ultrafast Optics and X-Ray Division, Center for Free-Electron Laser Science / DESY, Notkestrasse 85, 22607 Hamburg, Germany 2 Department of Physics and the Hamburg Centre for Ultrafast Imaging, University of Hamburg Luruper Chaussee 149, D-22761 Hamburg, Germany 3 Department of Electrical Engineering and Computer Science, MIT-RLE, Cambridge, Massachusetts 02139, USA Hu ̈ seyin C ̧ ankaya1,2, Anne-Laure Calendron1,2 and Franz X. Ka ̈ rtner1,2,3 Pump: - Home-made Yb:KYW regenerative amplifier [6] - λ = 1030 nm, frep= 1kHz - Maximal pulse energy power EP = 4.8 mJ, τp= 700 fs White-Light 1: - 10-mm YAG (X1) - Lens: f = 100 mm (L1) - Collimation, off-axis silver mirror (C1), EFL=101.6 mm White-Light 2: - 3-mm YAG (X4) - Lens: f = 75 mm (L4) - Collimation, off-axis silver mirror (C4), EFL=50.8 mm Motivation Experimental set-up Experimental results References Conclusions High-energy pulses with multi-octave bandwidth are needed for efficient high-harmonics generation to obtain isolated-attosecond X-ray pulses. A laser driver based on frequency synthesis is a well-suited source for its flexibility in spectral shaping and scalability in spectrum and energy, as demonstrated in [1-3] Such a laser source supports efforts in sub-cycle pulse synthesis and coherent X-ray sources [4,5]. Energy scaling by amplification through optical parametric amplifiers (OPA) requires a broadband seed source.  Due to the direct electric field driven processes, carrier envelope phase (CEP) stability of the seed is required. Fig. 1: Layout of the setup consisting two white-light super-continuum, OPA and f-2f setups. [1] A. Wirth et al., " Synthesized Light Transients," Science 34, 195, (2011) [2] S-W. Huang et al., " High-energy pulse synthesis with sub-cycle waveform control for strong-field physics," Nature photonics, 5, 475 (2011) [3] O.D. Muecke, et al., "Millijoule-Level Parametric Synthesizer Generating Two-Octave-Wide Optical Waveforms for Strong-Field Experiments," San Jose, CLEO (2013) [4] G. Cirmi, et al. “High-Energy Sub-Optical-Cycle Parametric Waveform Synthesizer”,UP, Poster, 07.Mon.P1.55, Okinawa (2014) [5] S. Fang et al., “Above-Millijoule Optical Waveforms Compressible to Sub-fs Using Induced-Phase Modulation in a Neon-Filled Hollow-Core Fiber, ”,UP, Poster, 09.Wed.P3.60, Okinawa (2014) [6] A-L. Calendron et al. “High-energy kHz Yb:KYW dual-crystal regenerative amplifier” (manuscript in preperation) Fig. 3: White-light spectra pumped at 1 µm and 2 µm Fig. 4: Spectra out of the 2nd OPA. - We demonstrated passive CEP stable white-light continuum generation from 500 nm to 2 µm using slightly sub-picosecond pulses. - The optimal parameters for white-light generation with long driver pulses has been identified. - This source of CEP stable continuum is ideal for a two-octave wide high energy optical waveform synthesizer. - Outlook: - Amplification via OPA‘s. - Pulse Synthesis. Optical characteristics of OPA stages: Fig. 6: Fringes confirming the CEP stability of the white-light super-continuum in the range 950-1000 nm White-light spectra pumped at 1 and 2 µm: Regen Comp TFPλ/2L1X1 X2 X3 X4 TFPλ/2 TFP L2 L3 L5 Spect. X5 M1 M6 M2 C1 M3 C2 M4 C4 D1 M5 C3 PM L6 M7 BS White-Light 1 OPA 1 OPA 2 White-Light 2 f-2f L4 Fig. 2: Picture of the setup (OPA stages +WL2) White-light spectra pumped at 1 µm with transform- limited and chirped-pulses Long-term stability Δλs=210 nm Δλi=153 nm, Fourier limit 26 fs Eidler=7 µJ ΔEidler<2 % Passive CEP stability f-2f between white-light and SHG of idler CEP drift <200 mrad for 4 hour operation CEP preserved for the white- light continuum with long- driver pulses. Average over 1000 pulses CEP characteristics of White-Light 2: 1 µm driver pulses with 700 fs (FWHM) pulse duration [6] Fig. 7: CEP of the white-light super-continuum over 4 hours Average over 4 pulses OPA 1: - 4-mm BBO, θ=22° (X2) - Lens: f = 500 mm (L2), ωp0x=220 µm, ωp0y=180 µm, Curved mirror (C2, R=1m) - Ep=70 µJ OPA 2: - 6-mm BBO, θ=22° (X3) - Lens: f = 750 mm (L3), ωp0x=285 µm, ωp0y=260 µm, Curved mirror (C3, R=1.5m) - Ep=140 µJ (See poster P1.55) OPA 1 OPA 2 WL 2