Electrooptic light modulator including weighted interdigital electrodes

Abstract

In a light modulator wherein a modulator medium, such as an a-cut lithium tantalate plate, has a Pockels coefficient for converting one of orthogonally polarized components of a light beam to the other thereof in cooperation with an electric field produced in the medium in a direction predetermined relative to the thickness of the medium while the light beam is transmitted between a pair of end surfaces of the medium and wherein a voltage is supplied between that interdigital electrode pair to produce the electric field, digit electrodes of which are distributed along one of a pair of principal surfaces of the medium at a predetermined pitch between the end surfaces, weights are attached to at least those of the digit electrodes which are distributed adjacent to each end surface. Each weight-attached digit electrode contributes to conversion of the polarization to an extent determined by the weight attached thereto. The weights are gradually varied or reduced as the digit electrodes are distributed nearer to each end surface. It is possible to vary the weights by varying those parts of the electric field which are produced in the medium adjacent to the respective digit electrodes, as by varying the voltage supplied between each successive digit electrode pair or by varying the thickness. Alternatively, the weights are varied by varying the ratio of the width of each digit electrode to the gap by which that digit electrode is spaced from a next following digit electrode.