The shifts of the wavelength position that a radiation mode jumps from one longitudinal mode to the next in semiconductor lasers have been studied. The variation of the gain curve is found to depend not only on the junction temperature but also on the carrier density. The mode hops occur at different wavelengths and temperatures as the injection current changes. A systematic approach to controlling the temperature and current could extend the wavelength tuning range to a much greater extent. A wider tuning range will provide a free-running diode laser capable of readily reaching the specific atomic or molecular transition.
Ring-Ling Chien, "Shift of Mode-Hopping Wavelength in Single-Mode Semiconductor Lasers," Appl. Spectrosc. 47, 1716-1719 (1993)