Light Wave Synthesizer 20, a versatile front end for multi-PW few-cycle laser systems

Complete text of publication follows. The Light Wave Synthesizer 20 (LWS-20) is the first optical parametric chirped pulse amplifier (OPCPA) system with few-cycle pulse duration and 16 TW power worldwide. In LWS-20 pulses from an ultra-broadband oscillator, producing ∼ 5.5 fs pulses with 80 MHz repetition rate, are split for optical synchronization and one part of them is wavelength shifted to 1064 nm to seed a commercial pump laser producing up to 1 J, 80 ps, 10 Hz pulses at 532 nm. The main part of the oscillator energy is amplified in a Femtopower Compact Pro 1 kHz laser to 900 μJ energy and 25 fs duration. The broad seed spectrum for the optical parametric amplification (OPA) is generated by focusing into a tapered-hollow-core fibre filled with 2 bar neon. The cross-polarized wave generation technique is implemented after the compression of this broadened bandwidth to increase the temporal contrast by 4 orders of magnitude. The pulses are stretched in a specially designed grism stretcher to about 25 ps and amplified in two consecutive noncollinear OPCPA stages based on BBO nonlinear optical crystals. The supported wavelength range of the OPA is from 700 nm up to 980 nm, which corresponds to a Fourier limited pulse duration of sub-8 fs. The amplified pulses are compressed in a high transmission compressor containing bulk glasses of SF57 and quartz and by four chirped mirrors to about 8 fs. The pulse duration is optimized and tuned by an acousto-optical dispersive filter (DAZZLER). After the compressor a pulse energy of up to 130 mJ is reached with > 10 orders of magnitude contrast in the ± 25 ps temporal window and many orders of magnitude better outside this window. A Shack-Hartmann wavefront sensor and an adaptive mirror in a closed loop configuration are used to optimize the focusing properties of the laser to reach >> 1018 W/cm2 relativistic intensity on target. An upgrade in in progress to reach sub-5 fs pulse duration. Due to its practical spectral range, relative high energy, and good contrast the system id ideally suited as a front end for further amplification by Ti:Sa amplifiers into the multi-10-Joule range to reach ∼ 10 fs pulse duration and multi-Petawatt peak powers. After the sub-5-fs upgrade a further amplification by consecutive OPCPA amplifiers offers to reach a quasi-single-cycle, multi-Joule, multi-Petawatt OPCPA system to extend the attosecond physics to relativistic laser-plasma environment. Acknowledgements. We thank the supply of the tapered-hollow-core fibre to M. Scharrer and P.S.J. Russell.