Mid-infrared angled-grating distributed feedback laser

We report near-diffraction-limited output from an angled-grating distributed feedback type-II W laser emitting near 3.4 μm. For pulsed optical pumping of a 50-μm-wide stripe at 78 K, the far-field beam divergence angle was only 1.4°. The slope efficiency was 64% of that for a conventional Fabry–Pérot laser on the same bar. However, the spectral linewidth decreased by only a factor of 2. The beam quality was substantially better than that for the Fabry–Pérot laser out to stripe widths of at least 800 μm.