Sub-mA threshold 1.5-μm VCSELs with epitaxial and dielectric DBR mirrors

We report low threshold 1.5-μm vertical-cavity surface-emitting lasers with epitaxial and dielectric distributed Bragg reflector (DBRs). The device consists of a lattice-matched InAlAs-InAlGaAs DBR grown on an InP substrate, an InAlGaAs quantum well active region, a metamorphic GaAs tunnel junction, and a SiO ₂ -TiO ₂ dielectric DBR. The current confinement is achieved by oxidizing an AlAs metamorphic layer grown on top of the active region. Small aperture devices show a minimum threshold of 0.8 mA at room temperature in continuous-wave operation.