S. A. Frolov

Coherent combining of femtosecond pulses parametrically amplified in BBO crystals.

We report on the first experimental realization of coherent combining of parametrically amplified femtosecond pulses. The proposed and implemented two-loop active stabilization system allows us to achieve 110 as relative timing jitter between combined pulses, which is necessary for efficient coherent beam combining. In each channel of the two-channel laser setup, pulses were parametrically amplified in β-BaB2O4 (BBO) crystals to 50 μJ energy, compressed to 49 fs duration, and then coherently combined with efficiency as high as 97%. Currently, it is the shortest duration of amplified pulses for which coherent combining is demonstrated.

Coherent combining of multimillijoule parametric-amplified femtosecond pulses

We report on the first experimental realization of the coherent combining of multimillijoule parametric-amplified femtosecond pulses. An original two-channel laser system based on parametric amplification in β-BaB2O4 and LiB3O5 crystals was created. High-contrast laser pulses, with up to 100 mJ of energy and with a pulse duration of 23 fs, were generated in both channels. An original setup for active timing-jitter stabilization was developed. It allowed reduction of the relative timing jitter of the amplified pulses to 40 as, which enabled coherent combining with an efficiency as high as 95%. At the present time, this work demonstrates coherent combining of femtosecond pulses with both the highest energy and the shortest pulse duration.

High-intensity femtosecond laser systems based on coherent combining of optical fields

The basic design principles of high-intensity laser systems based on coherent combining of radiation of multichannel laser facilities are considered. The influence of the instability of parameters of individual beams on coherent combining efficiency is analyzed, and requirements on their values for realization of high-efficiency coherent combining are determined. The fundamental possibility of coherent combining of parametrically amplified femtosecond pulses is experimentally demonstrated for the first time. Combining pulses with an energy of ∼1 mJ (pulse duration of 25–30 fs) with an efficiency exceeding 83% is realized by using a spherical mirror and a specially developed high-precision electro-optical relative time jitter stabilization scheme, which ensures its stability at ∼170 as level. The analysis conducted and the experimental data confirm that there are no fundamental limitations on intensity scaling of the high-intensity laser system based on coherent combining being developed at the Institute of Laser Physics of the Siberian Branch of the Russian Academy of Sciences.

Design of high gain OPCPA for multiterawatt and petawatt class systems on large aperture LBO crystals

Comparative analysis of optimal scheme of non-collinear optical chirped-pulse parametric amplification of fewcycle femtosecond pulses from Ti:Sa laser in LBO and DKDP crystals pumped by picosecond pulses up to petawatt level is presented. A flexible code, based on the extended model of parametric amplification, which takes into account the large set of effects such as saturation, phase self-modulation, influence of beam divergence, thermal effects, and amplification of spontaneous emission was realized. A way of creating nearly 1 PW system based on LBO crystals with transform-limited pulse duration about 9 fs has been demonstrated. Comparison between DKDP and LBO crystal showed that the latter is much better for OPCPA petawatt system design than DKDP.

Ultrarelativistic laser systems based on coherent beam combining

Conceptual design for femtosecond laser system of exawatt class, based on multi-channel amplifier and coherent field combining of petawatt amplifier channels with phase-frequency controlled radiation by optical clock are discussed. The scheme of start petawatt level few-cycle laser system with stable phase-frequency parameters determinated by the accuracy of the optical standard based on parametric amplification in big-size LBO crystals pumped by picosecond pulses is analyzed.

Aberration-free broadband stretcher-compressor system for femtosecond petawatt-level laser system based on parametric amplification

An optimal stretcher-compressor scheme is designed for laser facilities based onbased on optical parametric chirped-pulse amplification under picosecond (∼100 ps) pumping, which enables one to attain petawatt peak power of pulses less than 10 fs with high contrast and low aberrations. The stretcher design is based on an Öfner telescope with spherical mirrors and two diffraction gratings, one being placed at the center of the spherical mirrors. It is shown to be the only possible aberration-free stretcher design. The simulation performed has shown that a compressor consisting of four transmission diffraction gratings with an aperture 112 × 125 mm, a thickness of 3 mm, and chirped mirrors with 100-mm aperture that introduce −4500 fs2 dispersion allows amplified pulse compression down to <10 fs length and 1 PW peak power with the total B-integral lower than 1. The designed stretcher-compressor system is planned to be implemented in the high power femtosecond laser system being developed at ILP SB RAS.

Dual-channel multiterawatt laser system with coherent beam combining

The dual-channel femtosecond laser system with each channel consisting of three BBO and LBO crystals based broadband parametric amplification stages of Ti:Sa laser radiation and relative jitter stabilization system to 110 as level is presented. For the first time coherent combining of two sequences of parametrically amplified femtosecond pulses with energy of ~ 150 mJ, 10 Hz repetition rate is experimentally realized. Coherent combining efficiency of over 90% is reached. Experimental results of parametrically amplified contrast measurement are presented with further comparison with simulation results based on the model of parametric luminescence evolution developed by us. In order to achieve petawatt power level schemes of multibeam pumping of the booster cascade of developed laser system are considered.