Abstract

A new type of resonator that generates an annular geometric mode by use of spherical mirrors has been developed. The four-element cavity consists of an external confocal unstable resonator with a double-sided 45° coupling mirror and a flat feedback mirror. The Flat feedback mirror is placed on the plane wave side of the confocal cavity to form an annular mode between the feedback mirror and the coupling mirror. A plane annular wave (matched to an annular gain medium) is fed back into the unstable resonator that alternately converges and diverges to produce a diverging annular output beam Experiments were performed on a cw HF laser. Observations of mode. patterns on the flat feedback mirror and the convex mirror and of. Far-field beam quality were made Far-field measurements indicated near-diffraction-limited beam quality far a peak on-axis intensity mode on the convex mirror A nearly uniform annular mode was observed on the flat feedback mirror.

© 1976 Optical Society of America

Annular (HSURIA) resonators: some experimental studies including polarization effects

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