Beam Steering in Photonic Crystal Vertical Cavity Semiconductor Laser Arrays

Coherently coupled arrays of vertical cavity surface emitting lasers (VCSELs) offer the potential of extended area coherent sources with high spectral purity, useful in a variety of applications in the high power (laser radar, optical communications, steerable sources) and low power (image processing, spectroscopic sensing, optical logic) regimes. A recently developed method for providing optical confinement is the introduction of a two-dimensional photonic crystal (PhC) pattern with a defect, etched into the top distributed Bragg reflector, to define multiple defect cavities in a VCSEL. A major achievement of this work is coherent coupling between the defect cavities, with both out-of-phase and in-phase coherent coupling. A qualitative and quantitative understanding of the optical characteristics of PhC VCSEL arrays was developed and demonstrated by the agreement between simulation and experimental results. We show the relative phase difference between the defect cavities can be varied with injection current during both continuous-wave and pulsed operation. This directly leads to the ability to dynamically vary the angular steering of the far field. Electronic beam steering from photonic crystal VCSEL sources are applicable to many communication application