Analysis of grating-coupled emission in lead-tin telluride diode lasers

The use of the grating-coupled emission concept with lead-tin telluride double-heterojunction diode lasers is analyzed theoretically. The GCE configuration is shown to be attractive for producing small divergence-angle emission from fixed-wavelength lead-salt devices, but to be of more limited interest for use with tunable lasers because of the small critical angle characteristic of the PbTe-air interface and because of the variation of the angle of emission with wavelength. The device structure studied is one incorporating a reflecting contact in close proximity to the grating, a feature which leads to resonant enhancement or reduction of the emission, depending upon the wavelength and the device dimensions.