Vertical cavity surface emitting laser

A vertical cavity surface emitting laser comprising:

• a multilayer film reflector, a first clad layer, an active layer, a second clad layer, and a second reflector in this order on a substrate, wherein the multilayer film reflector includes a first photonic crystal layer, a second photonic crystal layer formed on the first photonic crystal layer, and a third photonic crystal layer formed on the second photonic crystal layer, the first, second, and third photonic crystal layers each include a first medium and a second medium so as to have a refractive index changing periodically in in-plane directions of the substrate, the first medium is arranged in the first, second, and third photonic crystal layers such that the first medium has a diameter that is larger in the second photonic crystal layer than in the first photonic crystal layer, and that is larger in the third photonic crystal layer than in the second photonic crystal, the diameter in each of the photonic crystal layers being gradually diminishing as the distance to the second clad layer decreases, in each of the first, second, and third photonic crystal layers, light resonates in an in-plane direction and exits in a perpendicular direction, wherein the first, second, and third photonic crystal layers each contain no defect, wherein the first photonic crystal layer and the second photonic crystal layer are different from each other in composition, wherein the second photonic crystal layer and the third photonic crystal are different from each and wherein light exits in an output direction and wherein the third photonic layer is farther from the substrate in the output direction than the first photonic layer and the second photonic layer.