OPTICAL SWITCHING OF SPATIAL MODES IN LASERS WITH A SQUARE PUMP

We consider a class-A laser operating on the three Gauss-Hermite modes of the frequency-degenerate family m + n = 2, and deliberately break the cylindrical symmetry of the system assuming that the pumped region has a square section. Having identified in the parameter space region s of spatial mono-, bi-, tetra- and esa-stability, we analyze the poss ibility of inducing optical switching between coexisting states, by th e injection both of a signal with the same spatial distribution of the final desired stationary state and of a gaussian signal strategically positioned in the transverse plane. In either cases we demonstrate lo w energy switching, respectively without and with the necessity of con trol on the phase of the injected field.