Visible-range hybrid femtosecond systems based on a XeF(C-A) amplifier: state of the art and prospects

Results of experimental and theoretical investigations of the hybrid (solid state/gas) visible-range femtosecond systems THL-100 (IHCE SB RAS) and THL-30 (P.N. Lebedev Physics Institute) based on a Ti : sapphire front end and a photochemical XeF(C-A) amplifier are reported. The front end generates 50-fs optical pulses with the second-harmonic (475 nm) energy of up to 5 mJ. The active medium of the amplifier is produced in a mixture XeF2-N2 subjected to VUV radiation of xenon excited by an electron beam. The computer model is developed for calculating parameters of the XeF(C-A) amplifier, which is in a good agreement with experiments. In the THL-100 system with the 25-cm output aperture of the XeF(C-A) amplifier, a record visible-range femtosecond radiation peak power of 14 GW was obtained in a 50-fs pulse with the time contrast of above 108. The measured power of an amplified spontaneous emission of the XeF(C-A) amplifier in the angle of 0.2 mrad was 32 W. The result obtained testifies that the hybrid approach to the development of ultrahigh-power systems provides a high time contrast of radiation (greater than 1012 for the projected peak power of 100 TW). In the THL-30 system, prospects for shortening an amplified femtosecond pulse are studied and it is experimentally shown that by compensating a third-order dispersion in a hybrid system one can obtain pulses with duration of at least 27 fs with a recompression of amplified pulses in bulk glass. Also, a new phenomenon was observed of spectrum broadening and self-compression of negatively chirped femtosecond pulses in the visible range under a nonlinear interaction of wide-aperture beams with fused silica. This result opens prospects for development of the new methods of self-compression for femtosecond pulses that are lacking physical limitations on pulse energy and realisation of self-compression of amplified pulses in the output window of the XeF(C-A) amplifier.