Electron Beam Pumped Tunable Excimer Lasers.

Laser characteristics were studied extensively for the broadband rare gas halide excimers Xe(,2)Cl, Kr(,2)F, and XeF (C(--->)A). The trimer Kr(,2)F was first observed to lase during these investigations, while Xe(,2)Cl and XeF (C(--->)A) had been previously demonstrated. Since all three excimers have unbound ground states, a spectrally wide emission bandwidth is available for wavelength tuning. Other excimers with wide band fluorescence emissions--Ar(,2)F and KrF (C(--->)A) at 290 nm, XeCl (C(--->)A) at 345 nm, and Xe(,2)F at 630 nm--were studied but had gains too small to achieve laser threshold in a 10 cm transversely pumped laser cavity.\nSeveral system parameters were studied for each of the lasers. These included mixture optimization, variation of optical resonator configuration, and influence of different halogen donors and buffer gases. Tuning was accomplished by using cavity mirrors with different center wavelengths. Littrow prisms were not suitable as dispersive elements because of the relatively high insertion loss and the low gain-length product of the 10 cm cavity.\nThe trimer Xe(,2)Cl had a nominal peak wavelength of 518 nm, with a tuning range of ('(TURN))15 nm and a (DELTA)(lamda) of 20 nm (FWHM). Laser pulse widths were about 36 nsec, and were delayed by 35 nsec from the e-beam excitation current pulse. This delay was observed in the other lasers as well, and can be attributed to transient absorptions by molecular argon. Atomic absorptions by xenon metastables to Ryberg levels were identified in the laser spectrum. Kinetics of Xe(,2)Cl* were also studied, with the following results: a radiative lifetime of 135 (+75 -60) nsec; a CCl(,4) quenching constant of 6 (+OR-) 1 x 10('-10) cm('3) sec('-1); a xenon quenching constant of )A) had the largest laser output intensity. The peak wavelength was 486 nm, with a (DELTA)(lamda) of 10 nm and a tuning range of 30 nm. Pulse duration was ('(TURN))30 nsec. Xenon absorption lines were identified which belonged to the same series as observed for the Xe(,2)Cl laser.