Polarization distribution of thermally poled PVDF films, measured with a heat wave method (LIMM)

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Abstract
The heat wave method LIMM is used to measure polarization distributions of PVDF-films. The PVDF-sample is heated by the absorption of intensity modulated light at the surface of the sample, while the pyroelectric current is measured. The standard LIMM method is extended by the measurement of amplitude and phase of the pyroelectric current. A measuring procedure is given to obtain the current data with a high amplitude and phase precision. It is shown, that the basic LIMM equation is formally inverted by deconvolution, if both amplitude and phase of the pyroelectric current is known. A filtering concept is introduced for the analysis of measured data. The experimental method and the deconvolution procedure is experimentally tested with an antisymmetrically prepared two layer sample (bimorph-foil). The results show, that with LIMM, a resolution of the spatially dependent pyroelectric coefficient in the range of a few microns is possible. Pyroelectricity distributions are reported for thermally poled PVDF-films.