AMPLITUDE-MODULATION AND BEAM-STEERING PROPERTIES OF ACTIVE BINARY PHASE GRATINGS WITH RECONFIGURABLE ABSORPTION AREAS

By combining a binary phase grating and materials with a controllable absorption, it is shown theoretically that it is possible to modulate the light in a zero-order diffraction beam and that a high contrast le vel for the beam modulation can be obtained. The intensity of higher d iffraction orders also changes, but it is calculated that high contras ts cannot be achieved for these higher-order beams with the active gra tings that we examine, This specific modulator design that we use can be applied both for transmitted and for reflected light. Using the sam e ideas, one may build a beam-deflection device by varying the period of the grating by selectively changing the absorption levels in the gr ating. The deflection efficiency of the device can be improved compare d with other designs by use of a grating with a reduced intensity of t he nondeflected zero-order beam.