Abstract: The invention relates to a VCSEL structure based on a novel grating reflector. The grating reflector (1) comprises a grating layer (20) with a contiguous core grating region having a grating structure, wherein an index of refraction of high-index sections (21) of the grating structure is at least 2.5, and wherein an index of refraction of low-index sections (22) of the grating structure is less than 2. The core grating region defines a projection in a direction normal to the grating layer. The grating reflector further comprises a cap layer (30) abutting the grating layer (20), and an index of refraction of the cap layer within the projection of the core grating region onto the cap layer is at least 2.