Abstract

We utilized an intracavity-mode homogenizer to increase the number of transverse modes and improve the temporal stability of a linear phase conjugate resonator (PCR). Unlike conventional resonators in which intracavity lenses can be used to enlarge the mode volume, an equivalent PCR may not produce the same spatial and temporal characteristics. We attribute these effects to the nonuniform reflectivity of the PCM as a function of input angle and to gain competition. We increased the mode volume and improved the stability of the output beam by introducing a 20-cm long rectangular light pipe in conjunction with a phase aberrator. The light pipe mapped each region of the conventional mirror into a large number of spatial modes before striking the PCM. Thus, all regions of the conventional mirror experience the same reflectivity at the PCM. In four-wave mixing experiments, the light pipe increased the angular width of the PCM reflectivity from 10° (with no light pipe) to 25°, FWHM. In resonator experiments with the intracavity light pipe, the oscillation of a 3.5-mm diameter transverse mode could be controlled from on-axis operation to 11-mm off-axis. In addition, temporal instabilities in the output pattern were reduced.

© 1991 Optical Society of America