Thermal lensing and optical bistability in ferroelectrics

In a recently developed theory of thermal lensing by ferroelectrics under laser illumination, the sample temperature as a function of radius and time was expressed as an integral. It is now shown that this integral can be approximated by known functions in a form which is accurate to within 1% for practical experimental situations. The theory is extended to explain asymmetric thermal focusing by BNN (barium sodium niobate, Ba2NaNb5O15). The presence of optical bistability in PMN (lead magnesium niobate, Pb(Mg1/3Nb2/3)O-3), and PLZT (lanthanum doped lead zirconium titanate, Pb(Zr1-xTix)O-3:La) and its absence in BNN and Ce:SBN (cerium doped strontium barium niobate, Ce3+:SrxBa1-xNb2O6) is explained by the presence or absence of Fabry-Perot resonance. Possible sustained periodic relaxation oscillations are discussed.