The reliability of packaged laser diodes is heavily dependent on the quality of the die attach. Even a small void or delamination may result in a sudden increase in junction temperature, eventually leading to failure of the operation. The contact thermal resistance at the interface between the die attach and the heat sink plays a critical role in thermal management of high-power laser diode packages. This paper focuses on the investigation of interface contact thermal resistance of the die attach using thermal transient analysis. The structure function of the heat flow path in the T3ster thermal resistance testing experiment is utilized. By analyzing the structure function of the transient thermal characteristics, it was determined that interface thermal resistance between the chip and solder was 0.38 K/W, while the resistance between solder and heat sink was 0.36 K/W. The simulation and measurement results showed excellent agreement, indicating that it is possible to accurately predict the interface contact area of the die attach in the F-mount packaged single emitter laser diode. Additionally, the proportion of interface contact thermal resistance in the total package thermal resistance can be used to evaluate the quality of the die attach.

High-power, broad-area, semiconductor lasers are attractive sources for material processing, aerospace, and laser pumping. The design of the active region is crucial to achieve the required high power and electro-optical conversion efficiency, since the temperature significantly affects the performance of the quantum well, including the internal quantum efficiency and mode gain. In this work, the temperature effects on the active region of a 808 nm high-power semiconductor laser were investigated theoretically and experimentally. The simulations were performed with a Quasi-3D model, which involved complete steady-state semiconductor and carrier confinement efficiency combined with a new mathematical method. The critical aluminum content of the quantum barrier was proposed and the relationship between temperature and various loss sources was disclosed in the temperature range of 213 to 333 K, which provides a reliable reference for the design of epitaxial structures of high-power semiconductor lasers in different operating conditions. Subsequently, the optimized epitaxial structure was determined and used to fabricate standard laser bar chips with a cavity length of 2 mm. The experimental electro-optical conversion efficiency of 71% was demonstrated with a slope efficiency of 1.34 W/A and an injection current of 600 A at the heatsink temperature of 223 K. A record high electro-optical conversion efficiency of 73.5% was reached at the injection current of 400 A, while the carrier confinement efficiency was as high as 98%.

Laser Power Transmission is emerging as a highly promising method for wireless energy transfer, particularly for extending the operational endurance of small unmanned aerial vehicles and supporting the construction of space-based solar power stations. This study investigated the optimal operational parameters of single-junction gallium arsenide (GaAs) photovoltaic (PV) cells under laser diode irradiation to enhance the efficiency of LPT systems. A detailed theoretical analysis was conducted to examine the effects of incident light intensity and spot size on the photoelectric conversion efficiency of GaAs PV cells across different temperature ranges. Experimental results demonstrated that as the temperature decreases from 55 °C to 5 °C, the incident intensity required for the photovoltaic cells to achieve peak efficiency rises from 0.35 W cm⁻² to 0.65 W cm⁻². Consequently, higher incident intensities are necessary for optimal efficiency when PV cells operate at lower temperatures. The 2 cm photovoltaic cells can attain a conversion efficiency exceeding 50% only when exposed to a 2 cm incident light spot. Therefore, high efficiency in photovoltaic cells is attainable solely when the size of the incident light spot is as closely matched to the cell’s size as possible. Additionally, this study provides an in-depth discussion of factors limiting photoelectric conversion efficiency and the underlying mechanisms at various temperature conditions.