Optimized second-harmonic generation in quantum cascade lasers

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 2 W of SHG light at 3.75 m wavelength at a fundamental peak power and wavelength of 1 W and 7.5 m, respectively. These lasers resulted in an external linear-to-nonlinear conversion efficiency of up to 1 W/W 2. An improved 2-QW active region design at fundamental and SHG wavelengths of 9.1 and 4.55 m, respectively, resulted in a 100-fold improved external linear-to-nonlinear power conversion efficiency, i.e. up to 100 W/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 10 5 (2 10 4 pm/V) is calculated, about two orders of magnitude above conventional nonlinear optical materials and bulk III-V semiconductors.

Influence of doping density on electron dynamics in GaAs∕AlGaAs quantum cascade lasers

“…1 However, more than 20 years passed until the experimental realization was demonstrated by Faist et al at Bell Laboratories on an InP substrate. 2 Since then tremendous progress in QCL research has resulted in bidirectional, 3 multiwavelength, 3,4 ultrabroadband, 5 above room temperature continuous-wave ͑cw͒ operation, [6][7][8] sum-frequency and higher order harmonic generation, [9][10][11] and fully integrated electrically pumped Raman lasers. 12 Moreover, laser operation has been reported on other material systems, i.e., AlGaAs on a GaAs substrate 13 and Al͑Ga͒Sb on InAs.…”

Genetic algorithm applied to the optimization of quantum cascade lasers with second harmonic generation

“…(2), while at the same time the active region continues to match the existing injector/collector regions described in Ref. 19. The energy difference DE 21 , defined by the LO phonon energy together with the transition energies between the levels constituting the cascades, DE 32 , DE 43 , and DE 54 , should remain unchanged.…”

“…19, i.e., 1000 lm 2 . n x ¼ k x c/x and n 2x ¼ k 2x c/x are refractive indices of the fundamental and second harmonic mode, Dk ¼ 2k x À k 2x the phase constant mismatch, and a 2x is the total loss including both the waveguide a w 2x and the mirror loss a m 2x .…”

“…II-IV, we wish to address the optimization of the resonant second-order susceptibility in a two-QW active region mid-infrared (MIR) QCL. 19 The optimal potential profile that maximizes the product of dipole matrix elements (DMEs) relevant to x ð2Þ associated with SHG is obtained via the Genetic algorithm (GA). The output properties of the reference and optimized structure are calculated by using the full self-consistent rate equation model, similar to the one used in our previous work described in Ref.…”

Aspects of the internal physics of InGaAs∕InAlAs quantum cascade lasers

“…[1][2][3] The first experimental realization of a QCL was demonstrated in 1994 by Faist et al at Bell Laboratories, Lucent Technologies, 1 some 20 years after the theoretical predictions by Kazarinov and Suris 4,5 of electrically pumped intersubband optical amplifiers. Since then there has been tremendous progress in QCL research, which has resulted in bidirectional, 6 multiwavelength, 6,7 ultrabroadband, 8 above room-temperature continuous operation, [9][10][11] operation in the terahertz region, 12 sum-frequency and higher order harmonic generation, [13][14][15] and fully integrated electrically pumped Raman lasers. 16 For further improvements a detailed knowledge of the crucial design parameters, as well as an understanding of the relevant physical limitations of particular designs, it is highly desirable to investigate the influences of the relevant physical and technological parameters.…”