We will present a detailed investigation of intersubband transitions process in core-multi shells quantum dots. The confined wave functions and eigenenergies of electrons in quantum dots have been calculated under the effective-mass approximation by solving a three-dimensional Schrodinger equation. Excellent dependence is found between size effects, time relaxation and degenerate four wave mixi...

The tunable terahertz intersubband Landau level transitions in resonant tunneling cascade quantum well structures are considered. The way of lifting the selection rule forbidding the inter-Landau level terahertz transitions of interest by applying a magnetic field tilted with respect to the structure layers is proposed. The importance of asymmetric structure design to achieve considerable value...

we will present a detailed investigation of intersubband transitions process in core-multi shells quantum dots. the confined wave functions and eigenenergies of electrons in quantum dots have been calculated under the effective-mass approximation by solving a three-dimensional schrodinger equation. excellent dependence is found between size effects, time relaxation and degenerate four wave mixi...

Frequency combs based on quantum cascade lasers (QCLs) are finding promising applications in high-speed broadband spectroscopy in the terahertz regime, where many molecules have their "fingerprints." To form stable combs in QCLs, an effective control of group velocity dispersion plays a critical role. The dispersion of the QCL cavity has two main parts: a static part from the material and a dyn...

We report on AlGaN/GaN multi-quantum-well structures displaying intersubband absorption in the THz spectral range. Firstly, we theoretically analyze the weaknesses of the state-of-the-art GaN-based step-quantum-well architecture from an optoelectronic standpoint. We then propose a modified geometry with improved structural robustness considering the uncertainties associated to the growth. This ...

The refractive-index nonlinearities of intersubband transitions in GaN/AlN quantum-well waveguides are investigated. A large spectral broadening of TM-polarized near-infrared pulses is observed after propagation through these devices due to intersubband self-phase modulation. From the measured data, a nonlinear refractive index n2 of 1.8 10 −12 cm2 /W is estimated at the operating wavelength of...

We investigate the spectral line shape of radiative intersubband transitions in a quantum well as determined by two factors: the electron scattering rate from states of given energy and the mass difference between the two subbands involved. The interplay between these factors leads to an essentially non-Lorentzian form of the spectral line. We develop an analytic theory of the line shape and ca...

This paper discusses the concept of enhancing semiconductor laser performance through tailoring of scattering rates of confined polar-optical phonons. Studies of optically pumped intersubband scattering in coupled quantum-well lasers have demonstrated that interface-phonon-assisted transitions are important in such structures; furthermore, simple analytical expressions have been derived that in...

The ideal performance of cascade and noncascade intersubband and interband laser active regions is directly compared in a cavity-insensitive way. For devices not limited by series resistance or series voltage ~such as can in principle be accomplished by cascading! the relevant figure of merit is the net material gain per unit volumetric power dissipation density in the active region. This figur...