Abstract

A multipass optical amplifier is described which makes use of the properties of a coupled pair of approximately confocal resonators. The departures of each resonator from the confocal condition, the relative orientation of the resonators, and the direction and convergence of the incident beam to be amplified can be varied to select a particular multipass arrangement. In general, these adjustments cause an incident light beam to pass alternatively through the two resonators and finally emerge after a number of traversals, which depends on the particular small departures of each resonator from the confocal condition. There are two basic configurations. In one configuration all the successive beam paths pass through one common crossing point which also coincides with the beam waists of the two resonators. In the second basic configuration, there are two spatially separated common crossing points, each of which coincides with the beam waist of one of the two resonators. A typical round trip transit time is ~2 ns. A number of variations of these basic configurations are discussed. Some allow a progressive change in the beam waist at the common crossing points, and some include dispersive elements which allow spectral filtering and group velocity dispersion correction.

© 1987 Optical Society of America