Inter and intra band impurity-related absorption in (In,Ga)N/GaN QW under composition, size and impurity effects

In this paper, we theoretically investigate the impacts of Internal well composition, size and impurity's position on the inter valence-conduction bands and intra conduction band optical absorption in GaN/(In,Ga)N/GaN hetero-structure. Based on the numerically finite element method (FEM), the impurity's related Schrödinger equation is solved for the finite potential barrier considering the dielectric constant and effective-mass mismatches between the well and its surrounding matrix. Our results show that the absorption is strongly governed by the dipole matrix element and initial and final implied states transition energies. For a fixed barrier width, the absorption spectra are found red-shifted (blue-shifted) with increasing the well width (In-concentration). It is also shown that the impurity's absorption phenomenon is more pronounced for the off-center case compared to the on-center one. We conclude that the proper control of these parameters is required to best understanding of the optical absorption for solar cell applications.

Waveguide-induced dispersion interaction between two two-level atoms with orthogonal in-transverse-plane dipoles

We study the dispersion interaction between two ground-state two-level atoms near a cylindrical vacuum-clad optical waveguide. We focus on the case where the electric-dipole matrix-element vectors of the atoms are perpendicular to each other and to the interatomic axis. When these atoms are in free space, the dispersion interaction between them vanishes. In the presence of a waveguide aligned parallel to the interatomic axis, the energy of the dispersion interaction between the atoms may become nonzero and comparable to the average energy of the dispersion interaction between two atoms with arbitrarily oriented dipoles in free space. This waveguide-induced dispersion interaction is a consequence of the anisotropy of the medium around the atoms.

Nonparabolic effects in multiple quantum well structures and influence of external magnetic field on dipole matrix elements

We present a method of modeling of nonparabolic effects (NPE) in quantum nanostructures by using second order perturbation theory. We apply this model on multiple quantum well structures and consider the influence of external magneticfield on dipole matrix element which is usually considered constant. The dipole matrix element directly influences the optical gain, and our model can provide a better insight to how NPE and magnetic field influence the gain of quantum nanostructures.

Analysis of dipole matrix element in quantum well and quantum cascade laser under the influence of external magnetic field

We present a method for modeling nonparabolicity effects (NPE) in quantum nanostructures by using second order perturbation theory. We will analyze application of this model on a quantum well without external electric field and a quantum cascade laser (QCL). This model will allow us to examine the influence of magnetic field on dipole matrix element in QCL structures which will give better insight how NPE can disrupt gain of QCL structures.

An analytical approach for the energy spectrum and optical properties of gated bilayer graphene

An analytical approach is developed to access the exact energy spectrum, wave functions, dipole matrix element (Mfi) and absorption spectra (A(ω)) of gated Bernal bilayer graphene.