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Proceedings Paper

Direct examination of turbulent refractive-index variations along laser beam propagation paths and corresponding optical-wavefront distortions
Author(s): Roberto C. Aguirre; Jennifer C. Nathman; Philip J. Garcia; Haris J. Catrakis
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Paper Abstract

A combined experimental/computational approach is conducted using a specially-designed laboratory facility and a physical framework based on refractive fluid interfaces in order to enable the direct examination of the turbulent refractive-index field along laser beam propagation paths, as well as of the corresponding optical-wavefront distortions of the propagated beam. The experimental facility utilized is the variable-pressure flow facility at UC Irvine which enables direct imaging of the turbulent refractive-index field at large Reynolds numbers in controlled laboratory flows. Laser-induced fluorescence of acetone vapor seeded in air is utilized to directly image the turbulent refractive-index spatial fluctuations along the beam propagation paths. A custom-built high-resolution Shack-Hartmann wavefront sensor is utilized that is useful to measure the optical-wavefront distortions of the propagated optical beam. The flow-imaging measurements, combined with the beam-wavefront data, enable a direct study of the correspondence between the turbulent refractive interfacial-fluid thickness variations and the beam-propagation parameters of interest in free-space laser communications such as the Strehl ratio. Combined with the experiments, computations are also conducted on the flow-imaging data in order to study the structure of the optical beam as it propagates through the measured refractive-index variations. This enables a one-to-one correspondence to be established between the refractive interfacial-fluid thickness variations encountered by the beam and their effect on the distortions of the optical wavefronts, quantified in terms of a cumulative Strehl ratio, along the entire propagation path examined through the flow.

Paper Details

Date Published: 31 August 2005
PDF: 12 pages
Proc. SPIE 5892, Free-Space Laser Communications V, 58920M (31 August 2005); doi: 10.1117/12.617802
Show Author Affiliations
Roberto C. Aguirre, Univ. of California/Irvine (United States)
Jennifer C. Nathman, Univ. of California/Irvine (United States)
Philip J. Garcia, Univ. of California/Irvine (United States)
Haris J. Catrakis, Univ. of California/Irvine (United States)

Published in SPIE Proceedings Vol. 5892:
Free-Space Laser Communications V
David G. Voelz; Jennifer C. Ricklin, Editor(s)

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