Terahertz radiation enhanced emission of fluorescence from elongated plasmas and microplasmas in the counter-propagating geometry
Abstract
Remote sensing is one of the major challenges for Terahertz (THz) radiation applications, due to the THz wave attenuation by the atmosphere water vapor during its propagation. THz-Radiation-Enhanced-Emission-of-Fluorescence (REEF) is a THz air-photonics technique that has the potential to bypass this issue, by having the sought-after THz spectral fingerprints carried from the target to the operator by ultraviolet light, which experiences low absorption in the atmosphere. This technique has been previously demonstrated when the THz radiation and the laser excitation are focused collinearly, namely, the co-propagating geometry. However, the co-propagating geometry is not a favorable configuration for practical stand-off detection. Therefore, further exploration on alternative sensing geometries is still required. Herein, we report the interaction of broadband THz radiation with plasmas induced by a counter-propagating laser beam, which is a more desirable geometry for remote sensing. We have found that in the counter-propagating geometry, the maximum amplitude of the REEF signal is comparable to that in the co-propagating case, whereas the time resolved REEF trace significantly changes. By performing the study with different plasmas, we observed that in the counter-propagating geometry, the shape of the REEF trace depends strongly on the plasma length and electron density. A theoretical model suggesting that the densest volume of the plasma does not contribute to the fluorescence enhancement is proposed to reproduce the experimental measurements. Our results further the understanding of the THz-plasma interaction and highlight the potential of the THz-REEF technique in plasma diagnostic applications.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Aug 28, 2017
- Source ID
- 10.1063/1.4990143
Entities
People
- Fabrizio Buccheri
- Kang Liu
- Xi-Cheng Zhang
Organizations
- Army Research Office
- Saint Petersburg State University of Information Technologies, Mechanics and Optics
- University of Rochester