Laser mode selection in multiarm grazing-incidence cavities

A four-arm grazing-incidence cavity (GIC) is demonstrated. It ensures stable single-made operation in a pulsed laser system by interferometrically enhancing mode selection; the corresponding standard GIC operates on five modes. We show that the four-arm GIC gives the best overall performance in terms of mode selectivity and threshold when compared with the standard GIC or with three-arm GIC's. In addition, an analysis of the interference effect is detailed that allows the four-arm GIC to be optimized for mode selection. Threshold gain and cavity losses are calculated, and the predicted mode spacing and complex reflectance are experimentally verified. (C) 1998 Optical Society of America.