Laser intensity modulation method (LIMM): A technique for determination of spatial distributions of polarization and space charge in polymer electrets

A new method for measuring the spatial distribution of combined polarization and space charge in poled polymer electrets has been developed. The technique, called the Laser Intensity Modulation Method (LIMM), is based upon measurement o-f the pyroelectric current generated by the electret when it is heated with a laser beam which is intensity-modulated at frequencies varying from 200 to 2500 Hz. A special analytical technique is used to trans-form the current-frequency measurements to spatial distributions. The advantages and limitations of LIMM are illustrated by means of calculations based upon simulated data. Experimental results on laboratory-poled samples are presented.