Intersubband transitions in semiconductor quantum wells are studied using a density matrix theory that goes beyond the Hartree-Fock approximation by including the full second order electron-electron scattering terms in the polarization equation for the first time. Even though the spectral features remain qualitatively similar to the results obtained with the dephasing rate approximation, signif...

Intersubband transitions from the ground state to the first and second excited states in pseudomorphic AlGaAs/lnGaAs/GaAs/ AlGaAs multiple step quantum wells have been observed. The step well structure has a configuration of two A1GaAs barriers confining an InGaAs/GaAs step. Multiple step wells were grown on GaAs substrate with each InGaAs layer compressively strained. During the growth, a unif...

We present the design, fabrication, and characterization of III-nitride quantum-well waveguides optimized for nonlinear-optical switching via intersubband transitions. A dielectric structure consisting of an AlN lower cladding and a GaN cap layer allows minimizing the propagation losses while maintaining a large modal overlap with the quantum-well active layer. A strong nonlinear saturation of ...

We present the design, fabrication and characterisation of an intersubband detector employing a resonant metamaterial coupling structure. The semiconductor heterostructure relies on a conventional THz quantum-cascade laser design and is operated at zero bias for the detector operation. The same active region can be used to generate or detect light depending on the bias conditions and the vertic...

Temperature dependence of intersubband transitions in AlN/GaN multiple quantum wells grown with molecular beam epitaxy is investigated both by absorption studies at different temperatures and modeling of conduction-band electrons. For the absorption study, the sample is heated in increments up to 400◦C. The self-consistent Schrödinger-Poisson modeling includes temperature effects of the band-ga...

Intersubband transitions in semiconductor quantum wells are studied using a density matrix theory that goes beyond the Hartree-Fock approximation by including the full second order electron-electron scattering terms in the polarization equation for the first time. Even though the spectral features remain qualitatively similar to the results obtained with the dephasing rate approximation, signif...

In this study, refractive index changes associated with intersubband transitions in a spherical quantum dot, GaAs/AlxGa1−xAs, have been theoretically calculated in the presence of impurity. In this regard, the effect of dot radius, stoichiometric ratio, impurity and incident optical intensity on the refractive index changes have been investigated for the transitions between higher energy states...

Semiconductor quantum wells are human-made quantum mechanical systems in which the energy levels can be designed and engineered to be of any value. Consequently, unipolar lasers based on intersubband transitions (electrons that make lasing transitions between subband levels within the conduction band) were proposed for long-wavelength sources as early as the 1970s. However, because of the great...

Most vapor molecules have a unique absorption spectrum in the mid-IR region, so this range is of particular interest for trace gas analysis and chemical sensing. And quantum cascade (QC) lasers are ideal candidate light sources for mid-IR spectroscopy: Their emission wavelength reaches from the midto the far-IR with good power efficiency. QC lasers are based on the intersubband transitions betw...

A theoretical study has been made to compare the quantum efficiencies of interwell and intrawell radiative transitions in quantum cascade lasers based on AlxGa1 xAs/GaAs technology. Radiative and non-radiative intersubband transition rates were calculated for a range of temperatures between 4 K and 300 K at an applied electric field of 4 kVcm 1 for structures designed to emit in both mid-infrar...