Low-threshold-current 670 nm multi-quantum-well laser diodes

There are increasing demands for low-power-consumption 670nm-band red-light-emitting laser diodes (LDs) in applications such as handy bar-code scanners, etc. In this paper the authors have developed low-threshold-current multi-quantum-well (MQW) LDs with a short-length-cavity and a high-reflectivity (HR) rear facet. Marked reduction in threshold currents has been achieved by using MQW as an active layer and by optimizations of cavity lengths considering temperature characteristics in a trade-off relation between low-threshold-currents and high-temperature-operations. Moreover, the reflectivity of a rear facet was increased to a maximum value (80%) where necessary monitor currents for an automatic-power-control could be maintained. For 150μm-long LDs, threshold current was reduced to 12.6mA (1/3 of conventional LDs), maintaining sufficient temperature characteristics for 50°C use. For 350μm-long LDs, consumption power was reduced to 1/2 of conventional LDs and long lifetimes at 60°C have been obtained