Local mirror temperatures of red-emitting (Al)GaInP quantum-well laser diodes by Raman scattering and reflectance modulation measurements

Temperature rises were measured on cleaved, uncoated mirror facets of junction-side-up mounted (Al)GaInP laser diodes as a function of the injection current by Raman spectroscopy via the Stokes/anti-Stokes phonon line intensity ratio and the phonon line shift as well as by reflectance modulation as a novel application for laser mirror characterization. Below the threshold current the temperature rise is due to Joule heating of the drive current across the ohmic resistor and is ΔT≅35 K at threshold. Above threshold a significant power-dependent heating caused by absorption of laser radiation is superimposed. In this regime the temperature increase is considerably high, i.e., ΔT≥100 K at 4 mW for 5-μm-wide ridge lasers. The different measurement techniques have produced consistent data.