Broad-stripe near-diffraction-limited mid-infrared laser with a second-order photonic-crystal distributed feedback grating

Electron-beam lithography was used to pattern a second-order photonic-crystal distributed feedback grating onto an antimonide type-II "W" laser emitting at /spl lambda//spl ap/3.7 μm. For pulsed optical pumping, the output beam was essentially diffraction-limited up to a stripe width of 150 μm, and remained no worse than eight times the diffraction limit for stripes as wide as 600 μm. This represents a considerable improvement over all previous mid-infrared semiconductor lasers with such broad stripes.