| 摘要 |
<p>A quantum cascade laser is configured so as to include a semiconductor substrate and an active layer which is provided on the substrate and has a cascade structure including multistage-laminated unit laminate structures 16 each including a quantum well emission layer 17 and an injection layer 18. Moreover, the unit laminate structure 16 has, in its subband level structure, an emission upper level 3, a lower level 2, and an injection level 4 of higher energy than the upper level 3, and light hv is generated by intersubband transition of electrons from the level 3 to the level 2 in the emission layer 17, and electrons after emission transition are injected into the injection level 4 of the subsequent stage via the injection layer 18. In addition, the emission layer 17 includes two or more well layers, and the first well layer closest to the injection layer of the preceding stage is used as a well layer for injection level formation. Accordingly, a quantum cascade laser capable of operation with high efficiency at high temperature can be realized.</p> |
