Cavity design for improved electrical injection in InAlGaP/AlGaAs visible (639–661 nm) vertical-cavity surface-emitting laser diodes

A novel optical cavity design for improved electrical injection in visible vertical-cavity surface-emitting laser (VCSEL) diodes employing an InGaP/InAlGaP strained quantum-well active optical cavity and AlAs/Al0.5Ga0.5As distributed Bragg reflectors (DBRs) is described. The cavity design was determined by measuring the lasing threshold current density of visible edge-emitting laser diodes with AlAs/Al0.5Ga0.5As DBR cladding layers. By inserting InAlP spacer layers between the active region and the DBR cladding, significant improvement in the performance of the edge-emitting lasers was achieved. This approach was then applied to the design of visible VCSEL diodes, and resulted in the first demonstration of room-temperature electrically injected lasing, over the wavelength range 639–661 nm. The visible VCSELs, with a diameter of 20 μm, exhibit pulsed output power of 3.4 mW at 650 nm, and continue to lase at a duty cycle of 40%. The threshold current was 30 mA, with a low threshold voltage (2.7 V) and low series resistance (<15 Ω).