@article { ISI:000179399000011,
	title = {Minimal group refractive index dispersion and gain evolution in ultra-broad-band quantum cascade lasers},
	journal = {IEEE PHOTONICS TECHNOLOGY LETTERS},
	volume = {14},
	number = {12},
	year = {2002},
	month = {DEC},
	pages = {1671-1673},
	publisher = {IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC},
	type = {Article},
	address = {445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA},
	abstract = {The group refractive index dispersion in ultra-broad-band quantum cascade (QC) lasers has been determined using Fabry-Perot spectra obtained by operating the lasers in continuous wave mode below threshold. In the wavelength range of 5-8 mum, the global change of the group refractive index is as small as +8.2 X 10(-3) mum(-1). Using the method of Hakki and Paoli, the subthreshold gain of the lasers has furthermore been measured as a function of wavelength and current. At the wavelength of best performance, 7.4 mum, a modal gain coefficient of 16 cm(.)kA(-1) at threshold and a waveguide loss of 18 cm(-1) have been estimated. The gain evolution confirms an earlier assumption that cross-absorption restricted laser action to above 6 mum wavelength.},
	keywords = {mid-infrared, quantum cascade (QC) laser, semiconductor lasers, Semiconductor waveguides, waveguide measurements},
	issn = {1041-1135},
	doi = {10.1109/LPT.2002.804677},
	author = {C. Gmachl and Soibel, A and Colombelli, R and Sivco, DL and F. Capasso and Cho, AY}
}
