Abstract

The localized temperature at the facet of GaAlAs semiconductor diode lasers is of critical importance to laser degradation phenomena including catastrophic optical damage (COD). The spatial temperature distribution in the facet region of GaAlAs diode lasers was investigated with Raman microprobe spectroscopy. The thermal profiles and the heating and cooling dynamics of the facet areas were measured with 1-µm probe laser spots and 1-µs time resolution as a function of diode laser power and injection current. The 514-nm radiation from an Ar-ion laser was focused through a microscope onto the diode laser facet. The facet temperatures were determined by analyzing the Stokes-anti-Stokes ratio of the transverse optical phonon at ~270 cm^–1 in the Ga_1–xAl_xAs material. The high sensitivity of our custom-designed Raman system permitted the use of low Ar laser power (~1 mW) and time-resolved measurements at low duty cycle so that the perturbation of the temperature profiles by the probe light is minimized. Steep temperature gradients in excess of 100 K/µm were observed across the facet region with ambient temperature reached <5 µm away from the active region. When current pulses are injected in the GaAlAs diode laser the facet temperature appears to heat up on a microsecond time scale.

© 1989 Optical Society of America