Wavelength tuning of the stimulated emission from GaAs and CdSe electron-beam-pumped lasers

The wavelength at which the stimulated output from a number of electron-beam-pumped semiconductor lasers peaks is a function of the time after the start of the pumping pulse. In general, the output intensity reaches a maximum at short wavelengths considerably before it peaks at the longest. Detailed observations of the wavelength shifts of the peak output as a function of both time and pumping current are reported here for both CdSe and GaAs laser crystals. It is found that the rate of shifting of the wavelength peak (tuning rate) as a function of electron-beam pumping current is very similar in both functional form and magnitude in the two materials. Furthermore, the behavior of the tuning rate is dependent on whether or not lasing action occurs in the crystal under examination. For a crystal in which lasing action is obtained, the tuning rate saturates for pumping current densities above threshold. In contrast, for a nonlasing crystal, the tuning rate is a linearly increasing function of the pumping current density. The implications of these results are discussed with reference to previously reported work concerning shifts with respect to the band edge of the stimulated emission from semiconductor lasers.