Single transverse mode operation of GaN-based vertical-cavity surface-emitting laser with monolithically incorporated curved mirror

Abstract

We report single transverse mode operation of a blue GaN-based vertical-cavity surface-emitting laser (GaN-VCSEL) with a monolithically incorporated curved mirror. For a device with a 4 μm current aperture diameter and a curved mirror with a radius of curvature (ROC) of 51 μm, single transverse mode operation was confirmed up to an output power of 3.2 mW under continuous wave operation at 20 °C. For a device with a smaller ROC of 31 μm, multi transverse mode operation was confirmed, indicating that the transverse mode can be controlled by the cavity design of such GaN-VCSELs.

Narrow Emission of Blue GaN-Based Vertical-Cavity Surface-Emitting Lasers With a Curved Mirror

“…2(d) shows the relation between the ROC of the concave mirror and the FWHM of obtained FFP profiles. The relation between them is almost the same as one calculated through gaussian optics by Nakajima et al [16]. An FFP less than 5°was obtained when the ROC was greater than 170 μm, and an FFP of 3.9°was obtained when the ROC was 988 μm.…”

“…The ROC of the mirrors in these devices was 70-1000 μm, and all aperture diameters for current injection were 8 μm. A single transverse mode was obtained for devices with ROC values greater than 170 μm, indicating the modal width of the higher order modes overlapped sufficiently with the area outside the aperture to prevent lasing [16]. Conversely, for ROC values of approximately 70 μm, a multitransverse-mode behavior was observed due to the smaller beam size.…”

“…Moreover, since the concave-mirror provides strong lateral light confinement, the transverse mode can be stabilized even at a high optical output. Nakajima et al demonstrated single-mode operation at 6 × Ith or a light output power of 3.2 mW under room-temperature CW operation for a device with an aperture diameter of 4 μm [16].…”

“…For the curved mirror structure, the full-width at halfmaximum (FWHM) of the FFP has been reported to depend on cavity dimensions, for example, the radius of curvature (ROC) of the concave mirror [16], such that a larger ROC gives weaker optical confinement and a smaller FWHM of the FFP. It has been reported that the ROC value is controlled by changing dimensions of resins discs used for sacrificial mask for etching to obtain lens formation.…”

Electrically Injected GaN-Based Vertical-Cavity Surface-Emitting Lasers with TiO2 High-Index-Contrast Grating Reflectors

“…For III-nitride VCSELs, a challenge is to realize DBRs with proper optical, electrical, and thermal characteristics. Several implementations of DBRs have been reported, including epitaxial DBRs, − air-gap DBRs, nanoporous DBRs, , and dielectric DBRs, − but high contrast grating (HCG) reflectors have seldom been considered for GaN-based VCSELs. However, there have been many reports on HCGs and zero contrast gratings (ZCGs) in infrared-emitting VCSELs or vertical-cavity in-plane emission lasers (VCIELs) in the mature material systems, such as GaAs and InP, where lasing under electrical injection has been demonstrated. − …”