Beam quality issues for mid-infrared angled-grating distributed feedback lasers

Summary form only given. Considerable effort has been expended to develop semiconductor lasers that simultaneously exhibit both high output power and good beam quality. A promising approach is the angled-grating distributed-feedback laser (/spl alpha/-DFB), in which a diffraction grating is etched into the laser cavity at an angle /spl theta/ with respect to the facets. We illustrate the /spl alpha/-DFB geometry alongside a simple broad-area Fabry-Perot laser configuration. Both the cavity facets and the grating are necessary to produce angular-selective optical feedback in the /spl alpha/-DFB laser. We recently reported the first /spl alpha/-DFB lasers emitting in the mid-IR. We discuss optically-pumped mid-IR (/spl lambda/=3.4, 4.6 /spl mu/m) /spl alpha/-DFB (/spl theta/= 16/spl deg/) lasers with antimonide type-II "W" active regions, which display near-diffraction-limited far-field characteristics for stripes as wide as 50 /spl mu/m.