Epitaxial surface‐emitting laser on a lattice‐mismatched substrate Available to Purchase

We have demonstrated continuous‐wave, room‐temperature, photopumped operation of a vertical‐cavity surface‐emitting laser having a 0.8% lattice mismatch with its GaAs substrate. Such mismatch provides flexibility in designing resonators with new lasing wavelengths. The laser resonator comprises lattice‐matched In_0.12Ga_0.88As and In_0.10Al_0.90As quarter‐wave layers for mirrors and a strained‐layer superlattice of In_0.23Ga_0.77As/Al_0.35Ga_0.65As for an active region. The structure lases in the range 1.05–1.10 μm under continuous‐wave photoexcitation in the wavelength range 900–950 nm. The differential power efficiency is as high as 68% and the threshold is 2 kW/cm² (1.8 kA/cm² injection current‐density equivalent). Dislocation line densities observed by photoluminescence microscopy are about 6×10²/cm in both the active region and the uppermost mirror layers. The lines predominate along one 〈110〉 direction along which the laser light is preferentially polarized. These observations suggest a way of polarizing surface‐emitting lasers by intentional patterning of grating lines on the wafer surface.