Patent ID: 8374208
Filing Date: 2013-02-12
Classification: B82Y,H01S

Abstract:
1. A quantum cascade laser comprising: a semiconductor substrate; and an active layer which is provided on the semiconductor substrate and has a cascade structure formed by alternately laminating quantum well emission layers and injection layers by multistage-laminating unit laminate structures each including the quantum well emission layer and the injection layer, wherein each of the plurality of unit laminate structures included in the active layer has an emission upper level, an emission lower level, and an injection level as an energy level higher than the emission upper level in its subband level structure, light is generated by intersubband transition of electrons from the emission upper level into the emission lower level in the quantum well emission layer, and electrons after the intersubband transition are injected into the injection level in the unit laminate structure of the subsequent stage via the injection layer, and the quantum well emission layer includes n, n is an integer of 2 or more, well layers, and a first well layer closest to the injection layer side of the preceding stage is formed as a well layer for formation of the injection level.