Polarization and Modes control of GaN-based VCSELs with curved mirror

Abstract

VCSELs have attracted much attention in recent years and, particularly, GaN-based VCSELs, which allow visible laser emission, have potential applications as light sources for displays, illuminations, biosensors, and atomic clocks. The author’s group has been working on development of blue and green VCSELs having a unique structure where one side of mirror is curved [1]. This talk will report the past and the latest progress of the research. We already have reported kinds of results for blue VCSELs, such as a low threshold current of 0.25 mA [2], single transverse operation up to four mill-watts [3] and narrow emission angle of 3.9 degree [4] with precise control of curvature of the mirrors. We also have reported single longitudinal operation with SMSR of 40dB through modulating the mirror reflectivity [5]. Green VCSELs are one of the authors scopes with which we previously reported continuous wave operation of green VCSELs grown over {20-21} semi-polar plane that provide high efficiency of 3.6% [7] and white light generated only by VCSELs (See figure 1 left).As the latest results, we report unique mode controls through introduction of side facet (see figure 2 left) to the curved-mirror cavity that drastically impacts the status of transverse modes and polarization direction. For example, we obtained 50-µm-wide spatial coherence across 14 dots of vertical-cavity surface-emitting modes [8] (See figure 1 right) and stabilization of polarization modes [9] (See figure 2 right). We also report progress around efficiency and/or output power of these VCSELs that rewrite previous records of these kinds of devices.