Abstract: Provided is a vertical cavity surface emitting laser diode (VCSEL) with a small divergence angle. The VCSEL includes a multi-layer structure on a substrate. The multi-layer structure includes an active region and current confinement layers. Each of the current confinement layers has an optical aperture (OA). When the area of the OA of the current confinement layer outside the active region is larger than the areas of the OAs of the current confinement layers inside the active region, such that the VCSEL has a small divergence angle in the short pulse mode.

Abstract: Provided is a vertical-cavity surface-emitting semiconductor laser diode, including a substrate and an epitaxial stack structure disposed on the substrate. The epitaxial stack structure includes an active region, a current confinement layer and a mode filter layer. The mode filter layer includes an optical aperture, and the mode filter layer is able to be oxidized. Accordingly, the optical aperture of the mode filter layer is formed by oxidizing the mode filter layer.