| 摘要 |
A quantum cascade laser is configured by comprising a semiconductor substrate, and an active layer which is provided on the substrate, and which has a cascade structure in which a unit laminate (16) composed of a light emission layer (17) and an injection layer (18) is laminated in a multi-stage. The quantum cascade laser is also configured in such a manner that the unit laminate (16) has a first light emission upper level (Lup1), a second light emission upper level (Lup2) with higher energy than that of the first light emission upper level, a light emission lower level (Llow), and a relaxation level (Lr) with lower energy than that of the light emission lower level in the sub-band level structure, wherein light is generated by the transition of the electrons from the first and second upper levels to the lower level between sub-bands, and the electrons which have passed the transition between the sub-bands are relaxed from the lower level to the relaxation level, and are injected from the injection layer (18) to a light emission layer (17b) in the subsequent stage via the relaxation level. As a result, the quantum cascade laser capable of suitably obtaining light emission in a wide wavelength range is implemented. |
