Abstract
The linewidth enhancement factor α has been determined in GaInSbAs/GaSb lasers emitting near 1.8 μm (2 μm at RT) from the spontaneous emission spectra below threshold. For type-I lasers, where a p-n junction was located at the GaAlSbAs/GaSb heteroboundary, the measured α is 3.1 at the lasing wavelength at 82 K. In type-II lasers with the p-GaSb/GaInSbAs heterojunction α was estimated to be at least 2 times lower, that can be attributed to the formation of a quantum well structure at this heteroboundary under lasing conditions.