Spatially resolved self-heating and thermal impedance of laser diodes using CCD-TR imaging

The spatial distribution of the surface temperature of single and multi-section slotted semiconductor laser diodes with surface gratings is investigated experimentally with CCD-thermoreflectance imaging. The lasers are single frequency devices, operating at approximately 1550 nm. High resolution temperature maps of the laser ridge are obtained, with spatial resolution near 1 µm. The temperature profile in the direction lateral to the ridge is presented and a rapid decay in temperature away from the ridge is observed. Acquisition of the temperature maps takes about 8 minutes, with three maps required for a 400 µm device. The ridge temperature rise is shown to be linear with the power consumed by the diode. The temperature profile along the laser ridge is shown to be uniform within a section of the multi-section laser. The thermal impedance of the single section slotted laser and the various sections of the multi-section slotted laser were determined. It was found that the thermal impedance ridge length product (ZthL) was 40 ± 6 ° C µm/mW for all section lengths. Between sections a rapid decay is also observed.