We describe the use of an asymmetric feedback ring in an unstable resonator to obtain arbitrarily narrow-linewidth radiation across the full available aperture. We demonstrate its use with an electric-discharge XeCl laser to produce single-line radiation with a linewidth of 0.15 cm-1.
© 1988 Optical Society of America
D. Cooper, L. L. Tankersley, and J. Reintjes, "Narrow-linewidth unstable resonator," Opt. Lett. 13, 568-570 (1988)