Theses and Dissertations

ORCID

https://orcid.org/0009-0007-5813-6233

Advisor

Wang, Chuji

Committee Member

Henk, Arnoldus

Committee Member

Gombojav, Ariunbold

Committee Member

Pierce, Donna

Committee Member

Hossein Toghiani,

Date of Degree

12-12-2025

Original embargo terms

Visible MSU Only 1 year

Document Type

Dissertation - Campus Access Only

Major

Engineering (Applied Physics)

Degree Name

Doctor of Philosophy (Ph.D.)

College

James Worth Bagley College of Engineering

Department

Applied Physics Program

Abstract

This dissertation introduces optical trapping (OT) of single dust particles as a new diagnostic tool for probing low-temperature plasmas. By using focused laser beams to confine and transport individual microparticles, their trajectories can be analyzed to extract local plasma forces and electric fields with minimal perturbation. Two optical trapping systems were implemented: dual hollow-beam universal optical traps (UOTs) and loosely focused dual Gaussian-beam traps, both of which were integrated with a low-temperature plasma device, optical emission spectroscopy, and high-speed imaging. The technique was demonstrated in multiple plasma environments. Single particles were successfully trapped in atmospheric-pressure plasmas, including arc discharges, plasma jets, and dielectric barrier discharges. In RF plasmas, both transparent and absorbing particles, such as silica microspheres and carbon nanotubes, were confined and transported in three dimensions. Controlled transport was also extended to weakly magnetized plasmas, confirming the feasibility of single-particle diagnostics in magnetized environments. A major achievement of this work is the high-resolution mapping of radial electric fields in RF plasma sheaths. By moving a trapped particle across the sheath and applying a force balance analysis, detailed electric field profiles were obtained, with systematic variations observed as a function of gas pressure and applied RF voltage. Preliminary afterglow studies further revealed that dust particles retain significant charge after plasma extinction, producing accelerations beyond gravity and highlighting residual field effects. Collectively, these results establish optical trapping of single particles as a minimally invasive, versatile approach for sheath diagnostics, force and charge measurements, and magnetized plasma studies, opening new opportunities for both laboratory and applied plasma research.

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