High-Brightness and Ultranarrow-Beam 850-nm GaAs/AlGaAs Photonic Band Crystal Lasers and Single-Mode Arrays

Lasers with a waveguide based on a longitudinal photonic band crystal designed for 850 nm emission are investigated. They demonstrate ultranarrow vertical beam divergence of about 7deg full-width at half maximum without using corrective optics. A high internal efficiency of 93% is achieved. Broad-area 50-mum-wide stripe lasers with unpassivated facets show a high total output power of about 20 W in pulsed mode with far-field divergences of 9.5deg and 11.3deg of the slow and fast axis, respectively, equivalent to an ultrahigh brightness of 3×10⁸ Wmiddotcm^-2 middotsr^-1 and a low aspect ratio of only 1.2. Narrow ridge lasers with 5 mum stripes demonstrate more than 1.5 W maximum output power in continuous-wave operation. Large arrays with up to 256 uncoupled single-mode laser diodes demonstrate low threshold currents of about 70 mA per laser, independent of the number of lasers in the array.