High-power optical sources of femtosecond pulses on the base of hybrid laser systems with wide-aperture gas laser amplifiers

Abstract

The multi-stage hybrid laser system producing ultrashort pulses of radiation with peak power ~10¹⁴ - 10¹⁵ W now under developing at the Lebedev Physical Institute of the Russian Academy of Sciences is discussed. The distinctive feature of the laser system is direct amplification of ultrashort pulses produced by solid state laser system, first going through a prism stretcher with negative dispersion, in gas active medium without using a rather expensive and complicated grating compressor of laser pulses. Two hybrid schemes are being developed now based on the amplification of femtosecond pulses of the third harmonic of Ti:Sapphire laser at the wavelength 248 nm in the active medium of KrF laser amplifier, and on the amplification of the second harmonic of Ti:Sa laser at the wavelength 480 nm in the active medium of photochemical XeF(C-A)-laser excited by VUV radiation of an e-beam pumped Xe₂ lamp. The final stage of the laser system is supposed to be an e-beam pumped facility with a laser chamber of 60 cm in diameter and 200 cm long in the case of KrF laser, and with another laser chamber of 30-40 cm in diameter put into the former one in the case of XeF(CA) laser. The parameters of such e-beam facility are close to those of previously developed at the Institute of High- Current Electronics: electron energy ~600 keV, specific input power ~ 300-500 kW/cm³, e-beam pulse duration ~ 100- 200 ns. A possibility of using Kr₂F as an active medium with saturation energy 0.2 J/cm² for amplification of ultrashort laser pulses is also under consideration. There was theoretically demonstrated that the energy of a laser pulse at the exit of the final stage of the laser system could come up to ~ 17 J with pulse duration ~50 fs in the case of KrF laser, and ~75 J with pulse duration of 25 fs in the case of XeF laser. Two Ti:Sa laser systems producing ~50 fs pulses with energy ~0.5 mJ at the wavelength 248 nm and ~5 mJ at the wavelength 480 nm have been already developed and are being now installed at the Lebedev Institute. Preliminary