Photonic crystal laser diodes are characterized by low divergence angle and high brightness, but thermal effects have become a major obstacle to further improvement of output power and efficiency. The thermal characteristics of highpower photonic crystal laser diodes are of great importance to improve the output power and increase the lifetime. In this paper, the physical heat dissipation model of a single photonic crystal laser diode with CS-mount package is established. Steady-state thermal characteristics simulations are performed using the finite element method (FEM) and the influences of different parameters, such as solder, transition heat sink and heat sink on the thermal characteristics are analyzed. The simulation results show that the thickness and thermal conductivity of the heat sink materials are the main factors impacting the heat dissipation of the laser. The thermal resistance of the laser can be reduced effectively by using heat sink materials of high thermal conductivity. On the premise of ensuring wettability and reliability, the thickness of the solder layer should be decreased. A photonic crystal laser diode with a cavity length of 4 mm and a stripe width of 350 µm based on an optimized heat dissipation structure is designed and fabricated. The CW output power of 41.9 W, the vertical divergence angle of 18.48°and the thermal resistance of 1.54 K/W are obtained under the injection current of 50 A at 20 ℃.

The application of high-performance VCSELs is extending from consumer electronics to automotive applications. Wet oxidation is an important technology in the fabrication of VCSELs. In this paper, we studied the wet oxidation process and mechanism in order to accurately control the oxidation aperture and improve the power and the conversion efficiency. Current density distributions of VCSELs with different oxide apertures are simulated based on COMSOL Multiphysics. In the experiment, the output power, conversion efficiency and threshold current of single junction and five-junction 940 nm VCSELs varying with oxide apertures are measured. Five-junction VCSELs exhibit maximum power conversion efficiencies are more than 60% and slope efficiency are more than 5.28W/A with oxide aperture from 9 to 15 μm under room temperature pulse condition (50 µs pulse width, 0.5% duty cycle). In addition, 385-element five-junction VCSEL array exhibits maximum power conversion efficiency of 53.45%. The five-junction VCSELs can be used as the basic laser source for the automotive applications.

Photonic crystal laser diode bars have the advantages of low vertical divergence angle and high resistance to catastrophic optical mirror damage. However, with the increase of output power, the waste heat problem is becoming more serious, affecting the further improvement of laser performance. Therefore, it is of great significance to study the thermal characteristics of bars. In this paper, the fluid-solid coupling conjugate heat transfer model of a microchannel cooled photonic crystal laser diode bar is established through the finite element method (FEM) and computational fluid dynamics (CFD) numerical methods. The transient thermal behavior, steady-state characteristics, and temperature distribution of photonic crystal laser diode bars under continuous (CW) operating states are studied in detail. The simulation results show that the junction temperature is 55.48°C, and the thermal resistance is 0.48 K/W. The closer the emitter is to the bar center, the easier the thermal crosstalk occurs. In the experiment, the continuous output power of the photonic crystal laser bar is 112.13 W at 120 A, the junction temperature is 57.14 °C, and the thermal resistance is 0.50 K/W. The simulations of bars are consistent with the experiment.