Nonlinear properties of silica for picosecond ultraviolet pulse

The development of excimer lasers has led to the generation of very high power pulses in the UV. There is a potential for large increases in currently achieved power levels and a great deal of interest in conducting experiments with such ultrahigh power short duration pulses. As at longer wavelengths UV lasers are ultimately power-limited devices, the limit on power being due to optical nonlinear processes occurring in the materials of the laser and experimental arrangement, induced by the beam itself and degrading the quality or reducing the energy of the beam. Measurements of two-photon absorption at 249, 266, and 351 nm have been carried out on several materials, and the nonlinear refractive index has been measured at 351 nm. However, there is a need for further evidence to enable a proper design of UV lasers and on assessment of their power-limited performance

Nonlinear properties of silica and air for picosecond ultraviolet pulses

The nonlinear power limiting processes in silica and air are investigated for picosecond pulses at the KrF wavelength. The two-photon absorption coefficient and the nonlinear refractive index in silica are measured to be 0.06cm / GW and 1.7 x 10-13 e.s.u. respectively. A mechanism for the rapid spectral broadening in air based on Raman-enhanced four-wave mixing is proposed. Experimental evidence supporting this hypothesis is presented