Abstract

Semiconductor lasers emitting in the 0.98 µm wavelength regime are promising for pumping optical fiber amplifiers and solid-state lasers. Although the short wavelength lasers are typically observed to have a high characteristic temperature T₀, their differential efficiencies often decrease rapidly with temperature increase. This deterioration of laser performance can cause serious problems in many applications. In this work, we investigate the physical causes of this temperature dependence experimentally as well as theoretically with buried heterostructure InGaAs/InGaAsP/InGaP strained quantum well lasers. Laser bars of various cavity lengths were measured at temperatures between 10°C to 160°C. Testing unbonded laser bars allows us to perform detailed measurements of many lasers with similar conditions. Thus, any unintentional variations due to fabrication or cleaving can be eliminated to achieve robust estimates of general laser characteristics. Results from these measurements show an increase in the internal loss with temperature, which we attribute to free carrier absorption. The internal efficiency is measured to not change significantly for temperatures less than 120°C for this laser design. The differential gain is measured to decrease with temperature, and this along with the increase in internal absorption can account for the increase in the threshold current density.

© 1994 Optical Society of America