FLASH-LAMP-PUMPED HO-TM-CR-YAG AND HO-TM-ER-YLF LASERS - MODELING OF A SINGLE, LONG-PULSE LENGTH COMPARISON

Two methods of producing the long pulse lengths that promote efficient extraction of energy from low-gain, quasi-four-level lasers are analy zed. A long pulse length output can mitigate laser-induced damage effe cts and can be generated in quasi-four-level lasers by two disparate m ethods. One method utilizes Q-switching techniques in resonators desig ned to extend the pulse length and another utilizes the first pulse in a relaxation oscillation pulse train. Models for quasi-four-level las ers are derived here taking into account the nonnegligible thermal pop ulation of the lower laser level. Closed-form expressions are derived for both modes of operation of quasi-four-level laser systems so the p arametric dependencies of both forms of operation become obvious, allo wing facile comparison. In addition, a combined absorption and quantum efficiency, germane for flash-lamp pumping, is calculated for both Cr and Er sensitizers. Although the former has the advantage of broad ab sorption bands, the latter has the advantage of a quantum efficiency a pproaching 3. (C) 1997 Optical Society of America.