Transverse mode selection by means of a convex-concave resonator in a
large-bore laser is investigated. The resonator parameters are calcula
ted and also measured experimentally. It has been shown that the reson
ator of this type is easier to construct and more convenient to use an
d under certain conditions has a better selectivity than conventional
telescopic resonators. Single-mode generation is achieved using the Ar
++ lines in the UV range.