Magneto-optical bistability in magnetic fluids: experimental evidence of multiple hysteresis cycles

V. Sofonea¹ - J.-C. Bacri² - R. Perzynski² - J. Servais²

¹ Research Center for Hydrodynamics, Cavitation and Magnetic Fluids, Technical University of Timisoara, Bd. Viteazul 1, R - 1900 Timisoara, Romania.
² Laboratoire d Acoustique et Optique de la Matiere Condensee, CNRS - URA 800, Universite Pierre et Marie Curi 13, Bo te 86, 4, Place Jussieu, 75252 Paris Cedex 05, France

Abstract
The bistable behavior of a hybrid magneto-optical device containing a magnetic fluid layer is experimentally investigated. The magnetic field acting parallel to the layer is the superposition of two components: a permanent component (Hs) and a variable one (Hf). The Hf component is controlled by the output laser beam intensity via a feedback loop. At constant input laser intensity, bistable behavior is observed when the device is subjected to variations of the amplification factor of the feedback loop or to variations of the permanent component Hs- Multiple optical tranamissivity hysteresis cycles are observed when the layer is thick enough and Hs is varied up and down over a large interval including the zero value. The width and the height of these cycles are found to be controlled by the amplification factor in the feedback loop. Figs 8, Refs 13.