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