Recent progress in vertical-cavity laser diodes

Vertical-cavity surface-emitting lasers (VCSELs) have shown considerable improvement in their operating characteristics during the past few years of concentrated investigations. These new laser diodes offer great potential as a compact light source for optoelectronics, optical communications, and optical storage. Among the various designs of surface-emitting laser diodes VCSELs have the lowest threshold currents and provide the highest packing density in two-dimensional arrays. VCSELs of submilliamp threshold currents, 1 above 100-mW cw output power 2 and high electrical to optical conversion efficiency of 15% as well as monolithic high-performance planar two-dimensional arrays of independently addressable VCSELs have been demonstrated. Most efficient VCSELs are being fabricated in the InGaAs-AlGaAs material system with emission between 800 and 1000 nm wavelength. Very recently, VCSELs with red and near-infra-red emission at 670 nm 3 and 1.3 μm wavelength, 4 respectively, have been realized.