From the studies on laser isotope separation by photomigration process, it isfound that pulsed irradiation is more effective than cw irradiation to enrich theobjective isotope. The optimum repetition rate of the pulses is 11. 1ms (90Hz), whenthe duty is 0.5. In this process, isotope compound to be separated is diluted with raregas, and is solidified on a cold plate. By laser irradiation, the selectively excited molecules migrate through rare gas matrix toward the cold plate to form fine crystals. It is confirmed that this enriching procedure can be superposed on a single cold plate. By changing the matrix composition of the Xe-Ar mixture matrix, the absorption peaksof isotope compounds can be shifted linearly in a limited wavenumber range (-6cm^-1).

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A high power 12.08μm NH₃ laser optically pumped by a TEA CO₂Iaser was developed for UF₆laser isotope separation. A rectangular metai waveguide was used to confine efficiently the energy of the pumping CO₂ laser. The output energy of 50 mJ (500kW) with the energy conversion efficiency of about 2% was obtained. The NH₃pressure dependence of the output energy and the characteristics of the polarization of the laser light were studied, and lasing mechanism was discussed from laser pulse shapes.
A 16μm CF₄ laser with the similar waveguide system was also developed. The output energy of 5mJ was obtained.

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The gain and line-narrowing of the amplified spontaneous emissions (ASE) in apartially homogeneous high-gain Xe 3.51 μm laser amplifier were studied theoretically and experimentally with emphasis of saturation effect. The unidirectionally travelling ASE was generated by conveniently using optical isolators and used as a broadband radiation source. It has properties of 10μW/mm² in intensity with fluctuation of less than 1% in 5hours, 43. 5MHz of the linewidth and 1, 0×10^-3 radians of beam diverg-nce. The measured saturation intensity was 4.85μW/mm² and a small signal gain was0.1cm^-1. The theoretical prediction of the line-narrowing shows reasonablly good agreement with the measured one.

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