Mode confinement in VCSEL-based photonic heterostructures

Summary form only given.Arrays of coupled vertical cavity surface emitting lasers (VCSELs) were previously shown to have a coherent photonic mode with high immunity against structural imperfections. In such periodic arrays the photonic mode stability depends on disorder in the position or size of the pixels, injection current, and boundary conditions. In the present work, we show that nonuniform VCSEL arrays with a properly designed variation in the lattice parameters can exhibit a new type of photonic confinement, namely confinement of the envelope function of the lattice modes. The resulting novel structures, that we term photonic heterostructures, confine photon modes much like semiconductor heterostructures that confine the envelope functions of charge carriers. The photonic heterostructures are fabricated in a similar way as other types of coupled arrays of VCSELs. They are based on GaAs/AlGaAs/InGaAs structures emitting through the substrate at 940-nm wavelength. Each photonic heterostructure consists of several rows of a lattice with larger, square pixels surrounded by a lattice of smaller pixels. The pixels are defined by covering their surface with gold acting as a reflection enhancing layer. The region between the pixels is covered with chromium.