Thermal properties of high-power diode lasers investigated by microthermography

摘要

Thermal properties of 808 nm emitting high-power diode lasers are investigated by means of micro-thermography.A thermo-camera equipped with a 384x288 pixel HgCdTe-detector (cut off wavelength at 5.5 micron) and IR-microobjectiveis used, which allows for thermal imaging with a spatial resolution of 5 μm. A novel methodological approachfor data re-calibration for absolute temperature measurements is proposed. We present steady-state thermal distributionsfrom broad-area devices. The remarkable agreement of this data with the results of modeling work has been reached.Cross-calibration of the micro-thermographic results is obtained by complementary micro-Raman data that giveinformation about facet temperatures with a spatial resolution of about 1 micron.Transient thermal properties are monitored with a temporal resolution of 1.4 ms. Such thermal transients illustratethe heat flow trough the device after turning on the operation current. Special experiments are done in order to detectand localize hot spots at the facet and within the devices. Moreover, we show that the analysis of thermal images can beused as a recognition method of defects hidden inside the cavity, even if they are not detectable by visual inspection.These activities are paving the way towards a novel screening methodology.