Red laser diode development for automotive applications

In recent years, red laser diodes (LDs) have been considered for automotive applications. The limitation of high temperature performance of AlGaInP-based red LDs has been one of the technological bottlenecks. Since the most important challenge was electron leakage from the active layer to the p-cladding layer, the p-cladding layer was applied AlInP with the highest band gap material and applied higher doping to minimize electron leakage. We fabricated two types of LDs, single-mode for high temperature operations and multi-mode for high power operations. Single-mode 642 nm 200 mW CW LDs were demonstrated. Optical output power at 350 mA reached 110 mW at 85°C and 90 mW at 90°C. Life test results showed stable operation in 2,000 hours at 85°C, 50 mW CW, and at -40°C, 200 mW CW. This red LD meets the high reliability requirements for automotive components. Also, Multi-mode 638 nm 4.2 W pulsed LDs were demonstrated. Optical output power at 6.0 A reached 4.6 W at 45°C and 3.5 W at 55°C. The estimated life time exceeding MTTF 20,000 hours at 45°C, 4.2 W pulse, frequency 240 Hz, duty 40%. In addition, 4.2 W at 45°C and WPE 45.6% at 25°C under pulsed operation are the world highest optical output power and WPE to the best of our knowledge. We believe that these excellent red LDs will be utilized for automotive applications in the future.