Comprehensive above-threshold analysis of antiguided diode laser arrays

The effect of gain spatial-hole burning (GSHB), carrier diffusion and interelement loss on antiguided laser arrays is thoroughly analyzed. Nonresonant devices, due to the nonuniformity of the in-phase-mode near-field intensity profile, experience self-focusing and multimode operation with increasing drive level above threshold, similar to evanescent-wave-coupled devices. Resonant and near-resonant devices (i.e., resonant-optical-waveguide (ROW) arrays) display substantially uniform in-phase-mode near-field intensity profiles at all drive levels, thus not allowing excitation of high-order modes (i.e., adjacent modes) due to GSHB at the array level. However, GSHB at the individual-array-element level eventually allows adjacent-mode lasing at high drive levels: ⩾10× fundamental-mode threshold for devices with relatively small ratio of element to interelement widths (so called fill factor): ~1.1; and ⩾7× fundamental-mode threshold for devices with moderate fill factor (~3) and 60 cm^-1 interelement loss. (The carrier diffusion length is taken to be 3 μm, and the index step, Δn, is moderate: 0.02-0.03). The calculations agree well with many experimental results, and confirm the inherent single-spatial-mode stability of ROW arrays. The model also predicts that high-index-step (Δn⩾0.1) ROW arrays are likely to achieve in-phase-mode stability to drive levels ⩾15× threshold, powers of ≈3W, in beams with ≈70% of the energy in the main lobe. Practical design guidelines are presented