@article { ISI:000186285800001,
	title = {Optimized second-harmonic generation in quantum cascade lasers},
	journal = {IEEE JOURNAL OF QUANTUM ELECTRONICS},
	volume = {39},
	number = {11},
	year = {2003},
	month = {NOV},
	pages = {1345-1355},
	publisher = {IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC},
	type = {Article},
	address = {445 HOES LANE, PISCATAWAY, NJ 08855 USA},
	abstract = {Optimized second-harmonic generation (SHG) in quantum cascade (QC) lasers with specially designed active regions is reported. Nonlinear optical cascades of resonantly coupled intersubband transitions with giant second-order nonlinearities were integrated with each QC-laser active region. QC lasers with three-coupled quantum-well (QW) active regions showed up to 12 muW of SHG light at 3.75 mum wavelength at a fundamental peak power and wavelength of 1 W and 7.5 mum, respectively. These lasers resulted in an external linear-to-nonlinear conversion efficiency of up to 1 muW/W-2. An improved 2-QW active region design at fundamental and SHG wavelengths of 9.1 And 4.55 mum, respectively, resulted in a 100-fold improved external linear-to-nonlinear power conversion efficiency, i.e. up to 100 muW/W-2. Full theoretical treatment of nonlinear light generation in QC lasers is given, and excellent agreement with the experimental results is obtained. For the best structure, a second-order nonlinear susceptibility of 4.7 x 10(-5) esu (2 x 10(-4) pmN) is calculated, about two orders of magnitude above conventional nonlinear optical materials and bulk III-V semiconductors.},
	keywords = {intersubband transitions, mid-infrared, multiple-wavelength emission, nonlinear optics, Quantum cascade laser, Quantum wells, second-harmonic generation},
	issn = {0018-9197},
	doi = {10.1109/JQE.2003.818315},
	author = {C. Gmachl and Belyanin, A and Sivco, DL and Peabody, ML and Owschimikow, N and Sergent, AM and F. Capasso and Cho, AY}
}
