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Advances in OptoElectronics
Volume 2010 (2010), Article ID 823157, 10 pages
http://dx.doi.org/10.1155/2010/823157
Research Article

Model for a Torsional-Mode Ultrasonic Transducer for an Acousto-Optic In-Fiber Isolator

Air Force Research Laboratory, Directed Energy Directorate, Kirtland Air Force Base, Albuquerque, NM 87117, USA

Received 29 October 2009; Accepted 22 January 2010

Academic Editor: Pierre Bourdon

Copyright © 2010 Gerald T. Moore. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Torsional ultrasound modes can couple the optical polarization states in a birefringent fiber. Polarization coupling produced by interaction with a higher-order torsional mode slightly above its cutoff may provide a route to producing an in-fiber isolator suitable for use in narrow-band high-power fiber amplifiers. This paper describes a model of a transducer generating torsional modes in a cylindrical fiber. This model predicts that almost all of the power applied to the transducer is radiated into the desired mode. The paper also discusses effects produced by acoustic absorption and the dependence of the acoustic velocity on temperature.