Optical response of layers of embedded semiconductor quantum dots

Abstract

The influence of the surrounding semiconducting matrix upon the polarizability of embedded nanoobjects ͑quantum dots͒ has been investigated. The previously proposed hybrid model has been extended to accommodate the influence of embedding. It turns out that excess discrete dipoles having an excess polarizability against a uniform background identical to the dielectric host material build the basis for a modified discrete dipole model, suited to describe the optical response of this system. The individual dipoles are described by means of dielectric embedded oblate ellipsoids as to their static response. An efficient description of the electrostatics of these ellipsoids has been given in terms of explicit functions using cylindrical coordinates and compatible with similar derivations for spherical dielectric objects. The dynamic contribution, responsible for frequency dependence is determined quantum mechanically and added to the embedded bare polarizability. The result of the model for the particular InAs quantum dot GaAs host combination investigated is a slightly decreased internal reflectance as compared to vacuum and an overall strong increment of the absorbance, the structure in the reflectance and of the ellipsometric angles.

Optical response of quantum dot multilayer structures

“…In the last equations: N u {u = x, y, z} and V denote the depolarization factor and the volume of the quantum dot, respectively. The inter-planar transfer tensor f is defined for two dimensional lattice of the quantum dots as: f x = f y = -f z /2, fz = 9.03362 [4],  EB,uu () is the polarizability of an isolated quantum dot defined in [4,5]. The polarizability includes the static and dynamic parts and the last one depends on the optical transition energies (E = ħ) [4,5,6].…”

“…Generally the metamaterials are designed as artificial multilayered structures. Optics of isolated layers of semiconductor quantum dots, quantum rings and quantum dot molecules was studied in details recently (see [4,5,6] and references therein). Therefore a proper modeling of the optical response from multilayered structures is on demand.…”

“…In this study we performed simulations of multilayered structures made from InAs lens-shaped quantum dots embedded in infinite GaAs matrix. In our model each layer is characterized by the reflection and transmission coefficients obtained in [5,6]. Based on the propagation-matrix approach [7] the overall reflection and transmission coefficients of multilayered structures are derived.…”

Low temperature and high magnetic field spectroscopic ellipsometry system

“…For example, nonmagnetic semiconductor nano-object based artificial materials have been proposed to exhibit magnetic-material-like collective optical responses which can be revealed by low-T and high-B ellipsometric measurements. [4][5][6][7][8] Another area of interest is the spatial dispersive exciton-polariton related problems, [9][10][11][12][13] for which the obliquely incident geometry of ellipsometry and high-B fields provide extra information of the momentum space parallel to the interfaces and the effect of spin configurations. We believe such a comprehensive study will help to develop the microscopic theory of exciton-polariton behaviors in magnetic fields.…”

Superluminality phenomenon at a femtosecond laser pulse propagation in a medium containing nanorods

“…[1][2][3][4][5][6] A large number of investigations deal with the optical response of a large ensemble of metal nanoparticles embedded into a medium and focus their attention on nonlinear refractive index changing and the third-order susceptibility changing in dependence of a nanoparticles concentration. [7][8][9][10][11][12] Obviously, a clarification of the physical mechanism for nanoparticle optical response dependence on the nanorods aspect ratio and nanorods orientation, and local enviroment, [13][14][15][16][17][18] as well as photothermal reshaping of nanorods or wires at the temperatures less than the bulk melting temperature [19][20][21][22] are very important questions. Various mathematical and physical models for an explanation of photothermal reshaping of nanosized nanoparticles are proposed up to now.…”