| 摘要 |
PROBLEM TO BE SOLVED: To provide a quantum cascade laser capable of improving characteristics such as injection efficiency of electrons into a light emission upper level. SOLUTION: This quantum cascade laser is formed by including a semiconductor substrate, and an active layer where unit laminated bodies 16 each composed of a luminescent layer 17 and an injection layer 18 are laminated in multiple tiers. A sub-band level structure of the unit laminated body 16 includes light emission upper level L<SB>up</SB>and lower level L<SB>low</SB>, an injection level L<SB>i</SB>on a high energy side, a relax level L<SB>r</SB>on a low energy side; electrons having passed through light emission transition from the upper level to the lower level are injected into the injection level of the luminescent layer at a rear stage from the injection layer 18 through the relax level, and electrons are supplied from the injection level to the upper level. Energy spacing between the injection level and the upper level is set larger than 10 meV and smaller than energy of an LO phonon, and light emission intensity from the injection level to the lower level is set smaller than the light emission intensity from the upper level to the lower level. COPYRIGHT: (C)2011,JPO&INPIT
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