Abstract

We report a simple technique for generating single frequency operation in an extended linear cavity. The technique requires the selection of a material with a strong absorption coefficient and a cavity mirror deposited on the surface of the solid state medium. If all the pump power is absorbed in a short distance from the mirror, all the longitudinal modes overlap spatially, thus each mode sees the same population inversion. The modification of the population inversion due to gain clamping by the first mode and the lower cross sections of other cavity modes prevents threshold. However, at some pump power, the contributions to the gain due to the spatial dephasing is large enough for other cavity modes to reach threshold. An analytical expression has been developed modeling this effect. In a nearly hemispherical laser cavity formed by a 2-mm sample of Nd:YVO4 and a 50-mm radius output coupler, pumped by a laser diode array, the threshold for laser emission is 40 mW. At 180 mW of incident pump power from a laser diode array, the single frequency output power is 35 mW.

© 1989 Optical Society of America