Electron Density Measurements for Plasma Adaptive Optics

Doctoral Dissertation

Abstract

Over the past 40 years, there has been growing interest in both laser communications and directed energy weapons that operate from moving aircraft. As a laser beam propagates from an aircraft in flight, it passes through boundary layers, turbulence, and shear layers in the near-region of the aircraft. These fluid instabilities cause strong density gradients which adversely affect the transmission of laser energy to a target. Adaptive optics provides corrective measures for this problem but current technology cannot respond quickly enough to be useful for high speed flight conditions. This research investigated the use of plasma as a medium for adaptive optics for aero-optics applications.

When a laser beam passes through plasma, its phase is shifted proportionally to the electron density and gas heating within the plasma. As a result, plasma can be utilized as a dynamically controllable optical medium. Experiments were carried out using a cylindrical dielectric barrier discharge plasma chamber which generated a sub-atmospheric pressure, low-temperature plasma. An electrostatic model of this design was developed and revealed an important design constraint relating to the geometry of the chamber.

Optical diagnostic techniques were used to characterize the plasma discharge. Single-wavelength interferometric experiments were performed and demonstrated up to 1.5 microns of optical path difference (OPD) in a 633 nm laser beam. Dual-wavelength interferometry was used to obtain time-resolved profiles of the plasma electron density and gas heating inside the plasma chamber. Furthermore, a new multi-wavelength infrared diagnostic technique was developed and proof-of-concept simulations were conducted to demonstrate the system’s capabilities.

Attributes

Attribute NameValues
URN
  • etd-04172014-154057

Author Brian W. Neiswander
Advisor Thomas C. Corke
Contributor Scott Howard, Committee Member
Contributor Eric H. Matlis, Committee Co-Chair
Contributor Stanislav Gordeyev, Committee Member
Contributor Thomas C. Corke, Committee Chair
Contributor Hyungrok Do, Committee Member
Degree Level Doctoral Dissertation
Degree Discipline Aerospace and Mechanical Engineering
Degree Name PhD
Defense Date
  • 2014-04-10

Submission Date 2014-04-17
Country
  • United States of America

Subject
  • ftir

  • dielectric barrier discharge

  • adaptive optics

  • plasma

  • aero-optics

  • electron density

  • interferometry

Publisher
  • University of Notre Dame

Language
  • English

Record Visibility Public
Content License
  • All rights reserved

Departments and Units

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