Effects of an aperture on transverse pattern stability and dynamics in a laser

Abstract

In studies of a model for transverse-mode interaction and spatiotemporal dynamics in a laser, three types of simple pattern formation have been found: the lowest-order transverse mode, temporally stable transverse patterns involving many empty cavity modes (known as a cooperative-frequency-locked state1 because all modes are locked to a common optical frequency), and the beating of two cooperative-frequency-locked states.2 The aperture affects laser operation most strongly in those regions in the parameter space (e.g., laser detuning from the material resonance and transverse-mode spacing) in which the time-dependent solutions are found in the absence of the aperture. In this case the aperture works primarily to suppress the beating and to compel the formation of frequency-locked states that are made up of many empty-cavity spatial mode patterns. Surprisingly, a lesser effect is that the aperture tends to force the laser to operate simply on the lowest-order transverse cavity mode. Results of our analysis indicate that the aperture may also distort the intermode spacings for different transverse modes and that this may also affect the tendency toward single-mode or single-frequency operation.