Indirect Temperature Measurement for Quasi-continuous-wavelength High Power Laser Diode Bars

High power laser diode bars (HPLDB) of quasi-continuous-wavelength operation mode with central wavelength 808nm are widely used in sensitive applications to the optical spectrum of emission. One such application is pumping of solid-state laser systems. HPLDB optical spectrum strong temperature dependence pushes engineers to use systems of thermal stabilization that always contains a thermal sensor. Nowadays the most popular thermal sensors are thermistors but there are also alternative approaches to measure the temperature of HPLDB is based on temperature dependences of HPLDB electrical and optical performance parameters. Thermistors need to be precisely mounted on the HPLDB submount far from the active laser zone so they aren’t able to detect fast thermal processes during injection current pulses because of large response time values. In this article some results of experimental research are presented. The results include temperature dependences of HPLDB optical spectrum, optical power and voltage drop both average and transient. Evaluations of transient temperature rise based on parameters values changes are made. The difference in independent approaches is less than $0.3^{\circ}\mathrm{C}$ which means that these methods can be used practically as an alternative to thermistors in HPLDB thermal stabilization systems. The method based on measuring voltage drop on HPLDB has an advantage in comparison to others, it doesn’t need any additional optical devices and aligning procedures. However, it is hard to measure absolute values of HPLDB temperature due to the complexity of epitaxial layers structure, cooling system considerations and non-ideality of the semiconductor manufacturing process. A calibration procedure can be performed during the tests for precise measuring of absolute temperature values of HPLDB.