Gallium nitride (GaN) vertical cavity surface emitting lasers (VCSELs) have attracted attention with their ability to emit in visible and ultraviolet (UV) wavelengths, affording a wide swath of exciting new applications in displays, solid-state lighting, sensing, and communications. Visible light communications (VLC) is a particularly attractive application for GaN VCSELs where they can be coupled with a phosphor to act as both a light source and data transmission device simultaneously. With the extensive proliferation of devices that can access networks, efficient data transmission has become a high priority, especially as bandwidths are becoming overcrowded. Realizing data transmission at visible wavelengths would greatly expand current bandwidth capabilities, but achieving this task will require solutions to the device degradation caused during lens growth and absorption loss within the long cavities of GaN VCSELs.
Researchers at the University of California, Santa Barbara have produced a GaN VCSEL that achieves high efficiency, high peak power, and long device lifetimes by eliminating degradation to the active region, improving emission intensity, and significantly reducing absorption loss within the cavity. Key to the invention is the topside dielectric p-side lens which provides the mode control characteristics. Topside fabrication eases pain points with processing and alignment in addition to putting more distance between the active region and the planar DBR. The topside lens allows for the active region to be farther up in the cavity, increasing the maximum width of the beam and current aperture. The use of wider apertures enables higher packing densities, positioning this VCSEL design especially well for high-power directional lighting applications or other applications where an array of VCSELs with a wide divergence angle is of interest.
III-nitride-based VCSEL, Vertical cavity surface emitting laser, GaN VCSEL, Dielectric p-side lens, Efficiency improvement, High peak power, Long device lifetimes, Active region degradation, Emission intensity improvement, Absorption loss reduction, Topside fabrication