Mukherjee, Shouvik
(2021)
Bose-Einstein condensation of polaritons in a ring microcavity.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Excitons are bound states of electrons and holes formed when light is absorbed in a semiconductor with a radiative lifetime typically of the order of a few nanoseconds. Putting these excitons inside a cavity allows them to mix strongly with the cavity photons, which creates a new quasi-particle called an exciton-polariton. These dressed photons have a small effective mass and an effective repulsive interaction, allowing them to thermalize and form a Bose-Einstein condensate within their lifetime.
In this thesis, I will report some recent experiments which I performed in the Snoke group on exciton-polariton condensation in a ring-shaped semiconductor microcavity. In a first set of experiments, the ring geometry along with a unidirectional force acting on the po-laritons helped us realize the rigid pendulum potential for the polaritons. Exciton-polaritons are monitored by detecting the photons leaking from the microcavity allowing us to observe real-time dynamics of the polariton condensate in the potential. I observed pendulum-like os-cillations of the polariton condensate which were damped about the potential minimum. By measuring the temporal evolution of the density and the spectral energy shift of the polariton emission, I made a direct measurement of the polariton-polariton interaction strength. In the course of these measurements, I found a non-equilibrium population of excitons traveling much further than previously anticipated, which demonstrates the anomalous “polariton ef-fect” on the transport of excitons. The polaritons constitute an example of a pseudospin-1/2 Bose gas which shows distinct properties from electrons in a semiconductor. By quenching a gas of polaritons in the rigid pendulum potential I observed the spinor dynamics, which showed characteristics of the optical spin Hall effect. The role of the free carrier reservoir on the energy dissipation of the condensate is theoretically investigated and applied to the interpretation of the recently observed “polariton drag effect”, in our group, where driving an electric current through the neutral polariton condensate produced momentum and energy shift of the condensate. These experimental and theoretical studies on transport and equilibration of the polariton condensate in narrow waveguide microcavities move towards making coherent polariton circuits for optical information processing.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
8 October 2021 |
| Date Type: |
Publication |
| Defense Date: |
28 April 2021 |
| Approval Date: |
8 October 2021 |
| Submission Date: |
29 July 2021 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
175 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Physics |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Microcavity, spin dynamics, dissipation, coherent optics, GaAs heterostructures |
| Date Deposited: |
08 Oct 2021 19:40 |
| Last Modified: |
08 Oct 2021 19:40 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/41531 |
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