A photonic crystal surface-emitting laser (100, 200), comprising: a first substrate; an n-type cladding layer disposed over the first substrate; an active layer disposed over the n-type cladding layer; and a photonic crystal structure disposed over the active layer; wherein the photonic crystal structure surface emitting laser (100, 200) is configured such that the light emitted by the active layer resonates in the photonic crystal structure and thereby produces a laser beam output from top of the photonic crystal structure along a direction normal to a plane of the photonic crystal structure; characterized in that: the photonic crystal surface-emitting laser (100, 200) further comprises an index matching layer disposed over the n-type cladding layer, wherein the index matching layer is arranged peripherally around the active layer and is in contact with a side surface of the active layer, wherein the index matching layer is electrically insulating, wherein the index matching layer is transparent to light emitted by the active layer, and an effective refractive index of the index matching layer is substantially identical to an effective refractive index of the active layer; wherein the photonic crystal structure is also disposed over at least part of the index matching layer, wherein a lateral length of the active layer is smaller than a lateral length of the photonic crystal structure, the active layer is located in an orthogonal projection area of the photonic crystal structure onto the n-type cladding layer, and the index matching layer is at least partially also located in the orthogonal projection area of the photonic crystal structure onto the n-type cladding layer. a first substrate; an n-type cladding layer disposed over the first substrate; an active layer disposed over the n-type cladding layer; and a photonic crystal structure disposed over the active layer; wherein the photonic crystal structure surface emitting laser (100, 200) is configured such that the light emitted by the active layer resonates in the photonic crystal structure and thereby produces a laser beam output from top of the photonic crystal structure along a direction normal to a plane of the photonic crystal structure; characterized in that: the photonic crystal surface-emitting laser (100, 200) further comprises an index matching layer disposed over the n-type cladding layer, wherein the index matching layer is arranged peripherally around the active layer and is in contact with a side surface of the active layer, wherein the index matching layer is electrically insulating, wherein the index matching layer is transparent to light emitted by the active layer, and an effective refractive index of the index matching layer is substantially identical to an effective refractive index of the active layer; wherein the photonic crystal structure is also disposed over at least part of the index matching layer, wherein a lateral length of the active layer is smaller than a lateral length of the photonic crystal structure, the active layer is located in an orthogonal projection area of the photonic crystal structure onto the n-type cladding layer, and the index matching layer is at least partially also located in the orthogonal projection area of the photonic crystal structure onto the n-type cladding layer. the photonic crystal surface-emitting laser (100, 200) further comprises an index matching layer disposed over the n-type cladding layer, wherein the index matching layer is arranged peripherally around the active layer and is in contact with a side surface of the active layer, wherein the index matching layer is electrically insulating, wherein the index matching layer is transparent to light emitted by the active layer, and an effective refractive index of the index matching layer is substantially identical to an effective refractive index of the active layer; wherein the photonic crystal structure is also disposed over at least part of the index matching layer, wherein a lateral length of the active layer is smaller than a lateral length of the photonic crystal structure, the active layer is located in an orthogonal projection area of the photonic crystal structure onto the n-type cladding layer, and the index matching layer is at least partially also located in the orthogonal projection area of the photonic crystal structure onto the n-type cladding layer.