Theoretical studies of the optical properties of photonic crystal and microcavity-based structures

Abstract

The work reported in this thesis is dedicated to the theoretical study of the certain properties of several types of resonant and nonresonant photonic nanostructures.
Negative refraction at the side edge of a Bragg reflector is studied. Analytical theory supported by numerical modelling using finite-difference time-domain (FDTD) simulations shows that the negative refraction in this case is equivalent to −1 order diffraction. Moreover, it is shown that a new effect, spatial oscillation of the Poynting vector of the transmitted radiation, can be observed under certain circumstances. In a separate
study the design of a spectral filter for the terahertz frequency range based on a metallic photonic crystal prism has been developed and refined. The theory makes use of the
complex band structure method together with FDTD simulations and shows that large angle separation of certain frequency component can be achieved with a prism due to the negative refraction effect. Experimental measurements on a device fabricated with a proposed design are also presented and confirm the theoretical predictions.
An optical eigenmode analysis of two organic microcavities separated by a thin metal layer has been carried out, both numerically and analytically. The analytical theory shows that the sharp reflections features observed in experimental reflectivity measurements are caused by the strong coupling of the Tamm plasmon modes present on both
sides of the metal film. Analytical theory is developed explaining the experimentally measured reflectivity spectra
of a one-dimensional photonic crystal with quantum wells embedded in its layers. The dispersion properties of the eigenmodes of the structure, originating from the strong coupling of quantum well excitons and photonic crystal modes are calculated. It is shown, that a new type of exciton-polariton, defined by the negative group velocity and effective mass can be observed in the structures.
A theoretical formalism and corresponding software code have been developed to model the kinetics of polariton lasers. The model is based on a Boltzmann equation approach
and accounts for electrical or optical pumping, polariton decay, and polariton-acoustic phonon, polariton-free electron and polariton-polariton scattering. The software code has been used to model the main characteristics of the specific GaN-based polariton lasers using parameters provided by experimental collaborators. It is predicted that the design of electrically driven polariton laser considered would have a threshold current density of 50 Acm−2 at room temperature.