STABLE RESONATORS FOR FUNDAMENTAL MODE-OPERATION

A general review of the laser resonator, characterized by its g parame ters, is presented. The stable configurations with one and two active media are considered. The laser rod is considered as a thick lens, wit h refractive power that depends on the pumping level. For the one-rod resonator, fundamental mode operation can be performed in two stabilit y zones. These zones are symmetrical and have the same width as a func tion of the refractive power of the rod. For a resonator with two rods inside, equal and different refractive powers of the rod at the same pump level are considered. By means of the g parameters and the resona tor matrix method, beam characteristics such as the spot size on the m irrors, divergence, beam waists and the positions of the beam waists, and the fundamental mode volume into the rod are described. To obtain fundamental mode operation, plane-plane and convex-concave resonators with one and two Nd:YAG active media are experimentally investigated. The results for energy, beam quality, and divergence are presented. (C ) 1996 Society of Photo-Optical instrumentation Engineers.