Efficient parametric conversion of infrared into ultraviolet radiation using sodium vapor

Reference is made to the work of Bloom et al. (1974), where the quasi-resonance parametric conversion (PC) in infrared pulses of wavelength 10.6 microns into ultraviolet light in sodium vapor is reported. It is noted that the energy efficiency of conversion per pulse in that study was rather low (approximately 8%), even though special measures were taken to heat the cell containing the nitrogen vapor uniformly and the interacting beams were focused with high accuracy. It is shown that it is possible to achieve a much higher (23%) conversion efficiency by using an axially nonuniform metal-vapor-buffer-gas medium; the pumping dye laser used has distributed feedback (DF laser) and the amount of underfocusing of the interacting beams is slight.