Abstract

Unstable resonators have always been an attractive configuration to extract efficiently the energy stored in a high-gain laser medium. However, this configuration gives an output beam with a hole in its center, which is inappropriate for frequency conversion or dye laser pumping. Polarization coupling can be used to avoid the presence of the hole, but the output beam uniformity is then very sensitive to thermally induced birefringence.

© 1988 Optical Society of America