A vertical microcavity (1) has a layer structure perpendicular to a vertical axis z, the layer structure comprising: a first reflector (100) and a second reflector (200), each comprising one or more material layers (111-131, 211-231) and being preferably a Bragg reflector, a confinement layer (10) separating the first and second reflectors, wherein an electromagnetic wave can be substantially confined, and wherein, the confinement layer comprises a body (12) and a defect (20), said defect delimited by two surfaces, a first surface (si) and a second surface (s 2 ), each of said two surfaces being perpendicular to the vertical axis z, wherein, one (si) of said two surfaces is contiguous with said body (12), the other one (s 2 ) of said two surfaces being contiguous with a layer (211) of the first or second reflector, and wherein one (s 1 ) of said two surfaces is curved, such as to have a curved profile (21, 21', 22) in at least a plane section ((y, z), (x, z)) perpendicular to the layer structure, said curved profile having a vertex (25), which defines a maximal thickness h 0 of the defect between the first surface and the second surface in said plane section, said maximal thickness h 0 being less than a thickness of said contiguous layer (211).