Nonlinear optical conversion of Nd:glass laser multimode radiation into the second harmonic in KDP crystal

Abstract

The second-harmonic generation (SHG) of Nd:glass multimode laser radiation in a 3 cm long KDP crystal has been studied both experimentally and theoretically for type I doubling at power densities of up to 2.5 GW cm −2 , radiation divergence of 0.5-3.5 mrad and between 100-1000 transverse modes. The theoretical calculations of SHG were performed in the fixed-field approximation, fixed-intensity approximation and in the nonlinear regime. The maximum experimental conversion efficiency of 52% was obtained for the case of partially polarized radiation with divergence of 0.5 mrad and 100 transverse modes.

High-energy laser facility PHELIX at GSI: latest advances and extended capabilities

“…It already exceeds 50% for 100-J square pulses of 2 ns duration, and saturates above 200 J of input energy. The nominal energy of 200 J in the frequency-doubled pulse is reached for about 270 J of input energy, showing a conversion efficiency of > 70%, close to the design point of the system and also compares well with the design goal of the crystal and with performances found in similar systems [51][52][53][54] . The 200 J SHG output is the upper limit allowed by the beamline design, which is limited by the laser induced damage threshold of the crystal coating and the coatings of the transport optics.…”