DYNAMICS OF TRAPPED POLARITONS IN STRESSED GaAs QUANTUM WELL-MICROCAVITY STRUCTURES: EXPERIMENTS AND NUMERICAL SIMULATIONS
Microcavity polaritons have been studied for a decade and a half. Soon after their discovery they were proposed as candidates for the observation of BEC in a solid. In consideration of this possibility, microcavity polaritons have been studied experimentally, analytically, and numerically. Most of the numerical studies have been qualitative. This thesis continues that analysis and for the first time fits experimentally obtained distributions with that obtained by numerical simulations.
For this thesis, experiments were performed on a GaAs quantum well-microcavity structure. Excitations of this structure are manifested as polaritons when the quantum well excitons are strongly coupled to the cavity mode. The experimental study of these polaritons provides interesting results. The experiments where the polariton density is the highest show that there is accumulation of polaritons in the low energy states near $k=0$. Below this high density it is seen that the distribution becomes flat and maintains that shape as density is decreased. Neither the high density nor the low density data has a thermalized distribution. Can the accumulation at high density be explained with Boson statistics? What can explain the flat, nonthermalized distribution at low densities. To answer these questions a numerical model was developed. The model has shown that the distribuition functions from the experiments can be numerically simulated. The model has shown that the accumulation at $k=0$ is due to Boson statistics. Through the model, an explanation as to why the distribution curves are flat is also provided.
This thesis is presented as follows. An introduction to microcavity polaritons and to our experimental system is presented in chapter 1. Chapter 2 describes the scattering processes that regulate the dynamics of the polaritons and the equations that are used in the model. Chapter 3 gives a review of previous numerical models on microcavity polaritons. Chapter 4 describes the experimental techniques used to acquire the data while chapter 5 compares the data with that given by the simulation. Chapter 6 then discusses directions for continued research.
Advisor:David Snoke; Robert P. Devaty; Robert Coalson; Rainer Johnsen; Kevin Chen
School:University of Pittsburgh
School Location:USA - Pennsylvania
Source Type:Master's Thesis
Date of Publication:01/28/2009