Abstract

We report the first experimental observation of a progression of allowed eigenmodes in a 10-element gain-guided diode laser array. By injection-seeding the array using the single-frequency output from a tunable cw dye laser, a sequence of eigenmodes of order 1–15 are selectively excited as the injected frequency is increased. Our results, in the form of observed near- and far-field intensity distributions emitted from these arrays, provide strong corroborative evidence for a model that views these devices as spatially gain-perturbed broad-area lasers whose characteristics are dominated by plane-wavelike interactions.^1,2 Consistent with this picture we find that lower-order (v < 10) modes can only be excited by optically injecting the entire width of the device. In contrast, the higher-order (v ≥ 10) modes, which exhibit larger tilts in their emission phase fronts with respect to the resonator axis, are more strongly coupled across the gain stripes of the device. These are thus easily excited by injecting the proper frequency radiation into a small region (≤ 5 μm) near the center of the array. From these studies the highest-gain eigenmodes are seen to be those for which v = 10 or 11. Indeed, these modes have been observed with the device operating in free-running conditions (i.e., no injection) near threshold. Our experimental results for both the free-running and injected arrays are compared to theory.

© 1986 Optical Society of America