Alternating Current Electric Field Driven Reconfigurable Random Lasing

Restricted (Penn State Only)
Author:
Donahue, Philip P
Graduate Program:
Chemistry
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 20, 2017
Committee Members:
  • Christine Dolan Keating, Thesis Advisor
  • Thomas E Mallouk, Committee Member
  • Raymond Edward Schaak, Committee Member
Keywords:
  • Random Laser
  • Lasing
  • Assembly
  • Dielectrophoresis
  • Nanoparticle
  • Microparticle
  • Photonics
Abstract:
Random lasing is a phenomenon in which random scattering media confine light within a gain region resulting in the production of sharp lasing modes. Nanoparticles suspended in laser dye solution are an example of a system that can facilitate this response. At sufficiently high scattering strength, fluorescent emission from dye solution undergoes multiple scattering events amongst the particles. This scattering extends the path length of light within the gain region, resulting in amplification of the emission wavelengths. Additionally, coherent resonance occurs with the scattering cavities made by the nanoparticles, which amplifies specific modes and results in lasing. The scattering events that govern these responses are a function of the nanoparticle characteristics relative to their surrounding medium. By using electric field enabled particle assembly techniques, parameters such as particle orientation, position, and concentration can be adjusted to influence random laser properties. Described here is the first example of nanoparticle assembly being used as a tool to control random lasing in a reconfigurable manner. Anisotropic titanium dioxide particle alignment is shown to tune the average effective particle scattering cross section, and in turn the lasing performance. Negative dielectrophoresis driven assembly of spherical particles is also presented as a potential means to control local scatterer number density, providing an additional degree of control over laser performance. Integrating particle assembly techniques with effects such as random lasing provides novel toolsets for the enhanced study of photonics, as well as a pathway to the advancement of nanoscale optical applications.