Author ORCID Identifier

https://orcid.org/0000-0002-6740-6588

Semester

Spring

Date of Graduation

2023

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Edward Flagg, Ph.D.

Committee Member

Matthew Johnson, Ph.D.

Committee Member

Mikel Holcomb, Ph.D.

Committee Member

Jeremy Dawson, Ph.D.

Abstract

Single photons emitted from self-assembled quantum dots have been widely studied to use as a promising qubit for quantum information processing. Therefore, it is critical to fully understand the emission spectra from the quantum dot's excitation if we want to use a single photon as a quantum bit. It is almost impossible to produce rotationally symmetric quantum dots due to various growth conditions and restrictions. So the real quantum dots do not have a perfectly symmetric structure. A broken rotational symmetry causes an asymmetric exchange interaction between electron and hole, leading to a fine structure splitting between two excited states. The energy structure of a neutral InGaAs self-assembled quantum dot can be envisioned as a V-shaped energy diagram. A three-level V-system gives Mollow septuplets or Mollow quintuplets depending upon the frequency of the excitation laser. The main focus of this dissertation is to design a tunable optical filter to explore Mollow septuplets and Mollow quintuplets. A grating spectrometer cannot resolve an emission spectrum of a semiconductor quantum dot (QD) due to its limited resolution. Typical frequency separations between features in the emission spectrum of a typical InGaAs quantum dots are 2-10 GHz, while the best resolution available for a commercial spectrometer is about 9 GHz. The solution is to use a Fabry-Perot interferometer (FPI) as a tunable optical filter. This technique demands precise control of the distance between the two FPI mirrors. One way to control the length of the FPI cavity is to use an optical feedback method to lock the cavity using a costly tunable, stabilized reference laser. Here we adopt an alternative approach that uses an inexpensive, single-frequency laser and spatial interference patterns to lock different interferometer designs. We mechanically connect the FPI cavity to a secondary cavity called a Shearing Interferometer (SI) that is actively stabilized by a simple and inexpensive optical feedback method.

Comments

Raju Bhai KC Ph.D. Dissertation Spring Semester 2023

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