Thermal focusing and optical bistability in ferroelectrics

O'Sullivan, R, McGregor, K and Scott, J 2001, 'Thermal focusing and optical bistability in ferroelectrics', Journal of Physics: Condensed Matter, vol. 13, no. 12, pp. 195-234.

Document type: Journal Article
Collection: Journal Articles

Title Thermal focusing and optical bistability in ferroelectrics
Author(s) O'Sullivan, R
McGregor, K
Scott, J
Year 2001
Journal name Journal of Physics: Condensed Matter
Volume number 13
Issue number 12
Start page 195
End page 234
Total pages 39
Publisher IOP Publishing
Abstract A review is presented of phenomena involving thermal focusing and optical bistability arising from the temperature dependence of the refractive index in ferroelectrics. Aperiodic spatio-temporal oscillations have been observed in the light transmitted and reflected by parallel-sided crystal and ceramic samples of the thermo-optic ferroelectrics PMN (lead magnesium niobate, Pb(Mg1/3Nb2/3)O3), PLZT (lanthanum doped lead zirconium titanate, Pb(Zr1-xTix)O3:La), BNN (barium sodium niobate, Ba2NaNb5O15) and Ce:SBN (cerium doped strontium barium niobate, Ce3+:Srx Ba1-xNb2O6) under steady illumination by an incident c.w. laser beam of finite beamwidth. Such materials focus the incident beam due to the temperature dependence of the refractive index and the establishment of a radial temperature gradient. The shape of the resulting thermal lens varies in time as a result of variation in the absorbed energy arising from both thermal focusing and optical bistability (Fabry-Pérot resonance). Whereas PMN and PLZT exhibit relaxation oscillations, the beam oscillations produced by BNN and Ce:SBN have equal rise and fall times. We compare the predictions of theoretical models with experimental results for ferroelectric ceramics and crystals. The principal conclusions from the present work are that (1) there are two distinct mechanisms for aperiodic oscillation in dispersively nonlinear plates, viz., focusing oscillations and Fabry-Pérot switching oscillations, of which only the latter involves bistability; (2) in Fabry-Pérot etalons with a diffusive nonlinearity, as contrasted with the systems (e.g. laser tubes) originally described by Gordon et al, the diffusive quantity (i.e. temperature) can exhibit bistable and multistable switching behaviour, leading to regenerative oscillations in other variables (e.g. light output); (3) there are two characteristic relaxation times involved in these oscillations, differing by several orders of magnitude; (4) the spatio-temporal characteristics of the transmitted beam patterns in the near and far fields can be quantitatively predicted and (5) comparison between theory and experiment can provide information on the temperature dependence of conductivity and thermo-optic coefficient near the ferroelectric phase transition.
DOI - identifier 10.1088/0953-8984/13/12/202
Copyright notice © 2001 IOP Publishing
ISSN 0953-8984
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