Highly-reliable operation of 638-nm broad stripe laser diode with high wall-plug efficiency for display applications

Laser based displays, as pico to cinema laser projectors have gathered much attention because of wide gamut, low power consumption, and so on. Laser light sources for the displays are operated mainly in CW, and heat management is one of the big issues. Therefore, highly efficient operation is necessitated. Also the light sources for the displays are requested to be highly reliable. 6 3 8 nm broad stripe laser diode (LD) was newly developed for high efficiency and highly reliable operation. An AlGaInP/GaAs red LD suffers from low wall plug efficiency (WPE) due to electron overflow from an active layer to a p-cladding layer. Large optical confinement factor (Gamma) design with AlInP cladding layers is adopted to improve the WPE. The design has a disadvantage for reliable operation because the large Gamma causes high optical density and brings a catastrophic optical degradation (COD) at a front facet. To overcome the disadvantage, a window-mirror structure is also adopted in the LD. The LD shows WPE of 35% at 25 degrees C, highest record in the world, and highly stable operation at 35 degrees C, 550 mW up to 8,000 hours without any catastrophic optical degradation.