Pulsed single-mode laser in four-arm grazing incidence cavity

A four-arm grazing-incidence cavity (GIC) is demonstrated. It ensures stable single-mode operation in a pulsed-laser system by interferometrically enhancing mode selection; the corresponding standard GIC operates on five modes. We compare the four-arm GIC with the standard GIC and with two other multiple-arm GICs and show that it gives the best overall performance in terms of mode selectivity and threshold. An analysis has been developed that allows cavity parameters to be optimized for mode selection. The analysis has been verified experimentally.