Photothermal approach to local heating imaging: application to laser degradation

We use various probes to measure local temperature induced by internal or external heating of active or passive devices: Mirage detection can reveal heating of few ppb of the input power, whereas photothermal microscopy provides sub-micron spatial resolution. Temperature distribution is measured through periodic deflection or reflectivity mapping at frequencies high enough to confine heating near the source. Scanning InGaAsP/InP lasers facets, shows the weak influence of nonradiative recombination, in agreement with the high output power of these lasers before degradation. On strained-layer InGaAs quantum well lasers we obtained a drastic temperature rise, that we explain through simple model based on line heating for the laser cavity and point heating located at the facet. On a damaged laser the result, demonstrate clearly the existence of heating zones far from the facet along the laser cavity.