LASER INTENSITY MODULATION METHOD (LIMM) - EXPERIMENTAL-TECHNIQUES, THEORY AND SOLUTION OF THE INTEGRAL-EQUATION

The Laser Intensity Modulation Method (LIMM) was developed for the determination of the spatial distribution of polarization or space charge through the thickness of a dielectric sample. It has been used in measurements on a number of ferroelectric ceramics and polymers, single crystals and pyroelectric glass-ceramics. Its applications have included poling studies, determination of crystallite orientation in glass-ceramics and influence of surface treatments on polarization of ceramics. The experimental technique and the theory are reviewed, and modifications for increase of accuracy are discussed. A major difficulty in the analysis of LIMM measurements is the necessity of solving a Fredholm integral equation of the 1st kind using experimental data. This is an ill-posed problem which can inherently yield a number of solutions, each of which satisfies the measured data to within experimental accuracy. A technique was developed for solving this class of equations by a modification of the constrained regularization method. The method was verified by experimental measurements on a lead-zirconate-titanate ceramic (PZT), polyvinylidene fluoride (PVF2), a glass-ceramic and multilayer samples composed of two or three sheets of PVF2, poled in either a positive or a negative direction or unpoled. © 1991, Taylor & Francis Group, LLC. All rights reserved.