Mapping of local temperatures on mirrors of GaAs/AlGaAs laser diodes

Abstract

Spatially resolved Raman scattering measurements (<1 μm) have been performed to determine the surface temperature distribution on coated and uncoated facets of ridge-waveguided GaAs/AlGaAs single quantum well graded-index separate-confinement heterostructure lasers. A strong nonlinear temperature versus output-power dependence is observed for cleaved, uncoated mirrors (ΔT>100 K for P>1 MW/cm2). Raman line scans show hot spot regions at the facets. Degradation strength correlates with facet heating. Disorder-activated Raman phonon modes indicate strong crystal damage. Laser mirrors with λ/2-Al2O3 coatings withstand up to 4–5 times the power density without significant heating and degradation. Local electroluminescence measurements along the cavity confirm increasing temperatures when approaching the facets and show that the resonator bulk material remains cold (ΔT<5 K).

Low-loss low-confinement GaAs-AlGaAs DQW laser diode with optical trap layer for high-power operation

“…These values are 2.7-3 times higher than those reported for symmetric GRIN structures not optimized for high-power operation [10]. For coated mirrors, these values should scale with a factor of 2.5 [8] or even 4-5 [12] and would correspond to at least about 88 mW/ m, which would be a factor of 2.7-3 times higher than for symmetric GRINSCH devices optimized for low threshold.…”

Improving lifetime of quasi-CW laser diode arrays for pumping 2-micron solid state lasers

“…As noted earlier, the excessive heating and drastic thermal cycling resulting from operation over the long pulse duration of 1 msec are the cause of premature failure and rapid degradation of these LDAs [4][5][6][7][8] . The current LDAs have an electrical to optical efficiency of about 50%.…”

“…Therefore, when running a 6-bar LDA close to full rating, about 600 W of peak power is generated in the form of heat, (7.2W average at 1 msec pulse duration and 12 Hz prf). This excess energy primarily generated in the active area of the bars (light emitting surface), is quite substantial [3][4][5] . For a typical bar with approximately 80% fill factor and 1 mm cavity length, the average heat flux is about 15 W/cm 2 and peak heat flux is over 1 kW/cm 2 .…”

Thermoreflectance spectroscopy—Analysis of thermal processes in semiconductor lasers

“…The scattering of the incident photons by phonons in a crystal leads to shift in energies of the out scattered photons and the creation or annihilation of an optical phonon. The probability of the inelastic scattering is temperature-dependent and is related to the occupation number of optical phonons [8]. Measurement of the crystal lattice temperature is given by the intensity ratio of the Stokes and anti-Stokes lines or by their spectral shift relative to the incident light [9][10][11][12].…”