Page 52 - Tunable Lasers Handbook

Lox ;Ilornos National Laboratory
Los Alamos. Neu, Mexico

D. G. Harris
Rochell inrernational
Canoga Park. California

1, INTRODUCTION

Excimer lasers are pulsed gas lasers that intrinsically offer efficient and pow-
erful broadband emission at several spectral regions throughout the ultraviolet.
The spectral widths are typically 2 nm. An exception to this categorization is the
XeF laser urith its broadly tunable C+A transition (approximately 50 nm) in the
visible. The broad tunability results from the steeply repulsive A state.
Excimer lasers have two primary formation channels for the excited state:
(1) recombination of positive rare gas ions with halide ions and (2) reactions of
excited rare gas atoms with halogen compounds [ 11.
The primary laser excitation techniques are high-energy electron beams.
electron beam sustained discharge, preionized avalanche discharges, neutron
pumping from reactors, and microwave excitation. The most useful of these have
been the pulsed electron beam and preionized avalanche discharge techniques.
The primary loss mechanism for a high-energy electron bseam (0.1 to 5
MeV) through a high-pressure gas is the creation of ion/electron pairs. Some
simple relationships may be used to relate the ion creation rate to the ionic reac-
tion channel for the formation of the upper laser state.
The details of electron beam devices have been reviewed by several authors
(see Ref. [l] for example) so only a brief description is given here. The electrons

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