We report a narrow divergence angle in a blue gallium-nitride-based visible vertical-cavity surface-emitting laser (GaN-VCSEL) with a curved mirror. This device exhibited continuous-wave operation at a wavelength of 450.9 nm. The full-width at half-maximum divergence angle of the 8 μm-aperture VCSEL was 3.9° when the device was operated at a current of 1.2 × Ith, where Ith is the threshold current. In this type of cavity, the radius of curvature (ROC) of the curved mirror determines the near-field pattern (NPF) and far-field pattern (FFP). The authors fabricated devices aving ROC up to 988 μm, which is more than 10 times greater than the ROC of the mirror used in the previously reported structures, allowing this narrow emission. The I–L characteristics showed that the Ith value increased with increasing ROC. The present study investigates the mechanism behind this tendency in detail.
