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Proceedings Paper

Superlattice quantum cascade lasers
Author(s): Alessandro Tredicucci; Federico Capasso; Claire F. Gmachl; Deborah L. Sivco; Albert L. Hutchinson; George Chu; Alfred Y. Cho
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Paper Abstract

Novel approaches to the design of inter-miniband quantum cascade lasers with undoped active regions are presented. The applied electric field is compensated across the superlattices, either by exploiting the field generated by extrinsic charges in special modulation-doped injection regions, or with an effective 'quasi-electric field' obtained by varying the superlattice period and duty-cycle so that a flat miniband condition is reached. Broadening mechanisms and optical losses introduced by the otherwise needed dopants in the superlattices are thus reduced, dramatically lowering the threshold current densities and improving the temperature performance of the lasers. At the same time the appealing properties of inter-miniband based devices, i.e. automatic population inversion and high current carrying capabilities, are preserved. Room temperature record-high peak (approximately 0.5 W) and average (14 mW) powers are observed for a (lambda) equals 7.6 micrometer laser. The lowest threshold current densities reported up to now in quantum cascade lasers at 300 K (Jth equals 4.5 kA/cm2) are also obtained, which translates in very large maximum temperatures for continuous wave operation (160 K).Inter- miniband superlattice structures prove particularly useful in extending laser operation towards longer wavelengths, where the increased optical absorption losses and the reduced radiative efficiency require larger driving currents. This is shown by the realization of a laser with chirped superlattice active regions operating at (lambda) equals 17 micrometer, well beyond the longest wavelength ((lambda) equals 13 micrometer) so far demonstrated for conventional quantum cascade lasers based on inter-subband transitions.

Paper Details

Date Published: 1 April 1999
PDF: 9 pages
Proc. SPIE 3628, In-Plane Semiconductor Lasers III, (1 April 1999); doi: 10.1117/12.344534
Show Author Affiliations
Alessandro Tredicucci, Lucent Technologies/Bell Labs. (Italy)
Federico Capasso, Lucent Technologies/Bell Labs. (United States)
Claire F. Gmachl, Lucent Technologies/Bell Labs. (United States)
Deborah L. Sivco, Lucent Technologies/Bell Labs. (United States)
Albert L. Hutchinson, Lucent Technologies/Bell Labs. (United States)
George Chu, Lucent Technologies/Bell Labs. (United States)
Alfred Y. Cho, Lucent Technologies/Bell Labs. (United States)

Published in SPIE Proceedings Vol. 3628:
In-Plane Semiconductor Lasers III
Hong K. Choi; Peter S. Zory, Editor(s)

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