Patent ID: 9484715
Filing Date: 2016-11-01
CPC Classification: H01S

Claim Text:
1. A quantum cascade laser comprising: a semiconductor substrate; a first active layer provided on the semiconductor substrate and having a cascade structure in which quantum well emission layers and injection layers are alternately stacked in the form of a multistage lamination of first unit laminate structures each of which comprises the quantum well emission layer and the injection layer; and a second active layer provided in series to the first active layer on the semiconductor substrate and having a cascade structure in which quantum well emission layers and injection layers are alternately stacked in the form of a multistage lamination of second unit laminate structures each of which comprises the quantum well emission layer and the injection layer, wherein the first unit laminate structure of the first active layer has a subband level structure having an emission upper level and an emission lower level, and is configured so as to be able to generate light of a first frequency ω the second unit laminate structure of the second active layer has a subband level structure having a first emission upper level, a second emission upper level of a higher energy than the first emission upper level, and a plurality of emission lower levels, and is configured so as to be able to generate at least light of a second frequency ω light of a difference frequency ω between the first frequency ω the second unit laminate structure of the second active layer is configured so as to be able to generate the light of the first frequency ω the quantum cascade laser being provided with a distributed feedback type oscillation mechanism by a diffraction grating for selecting the light of the second frequency ω