PT  - JOURNAL ARTICLE
AU  - Faist, Jerome
AU  - Capasso, Federico
AU  - Sivco, Deborah L.
AU  - Sirtori, Carlo
AU  - Hutchinson, Albert L.
AU  - Cho, Alfred Y.
TI  - Quantum Cascade Laser
AID  - 10.1126/science.264.5158.553
DP  - 1994 Apr 22
TA  - Science
PG  - 553--556
VI  - 264
IP  - 5158
4099  - http://science.sciencemag.org/content/264/5158/553.short
4100  - http://science.sciencemag.org/content/264/5158/553.full
SO  - Science1994 Apr 22; 264
AB  - A semiconductor injection laser that differs in a fundamental way from diode lasers has been demonstrated. It is built out of quantum semiconductor structures that were grown by molecular beam epitaxy and designed by band structure engineering. Electrons streaming down a potential staircase sequentially emit photons at the steps. The steps consist of coupled quantum wells in which population inversion between discrete conduction band excited states is achieved by control of tunneling. A strong narrowing of the emission spectrum, above threshold, provides direct evidence of laser action at a wavelength of 4.2 micrometers with peak powers in excess of 8 milliwatts in pulsed operation. In quantum cascade lasers, the wavelength, entirely determined by quantum confinement, can be tailored from the mid-infrared to the submillimeter wave region in the same heterostructure material.