turn, energizes the laser medium (Fig. 3(b)). Excess heat is dissipated by a heat exchanger loop and lasing conditions are controlled by a mechanical pump. This scheme is similar to a continuous wave (CW) laser system, except for the energy source and collector. Two aspects of cavity absorbers are important to solar-powered lasers. These are the radiator losses at the receiving aperture and the upper temperature limits imposed by materials used in the system. The advantages here are that heat losses of this body can be reduced by careful design, and the blackbody radiation spectrum at a selected temperature in the range 1500-3000 K for optimum pumping (as determined by the absorption bands and kinetic properties of a lasing medium) is selectively absorbed wherever there is an absorption band or line. Thus, a hole in the blackbody radiation spectrum develops, but the blackbody re-emits the same wavelength which can also be absorbed by the gas. Nearly all of the solar radiation is thus converted into the type of radiation necessary to pump the lasing gas. In this manner, utilization of the sun's energy could be much higher than by direct solar pumping. The use of blackbody radiation as a means of exciting molecular systems was proposed by Bokhan [17]. Laser systems composed of CO2 + N2 and CH4 +buffer gas excited by means of radiation from an oven have been considered; but no experimental work has been done. A demonstration of a blackbody-pumped CO2 laser was reported [18] by the same author, in which blackbody radiation was simulated by the emission from a
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