COMPLEX-AMPLITUDE MODULATION BY HIGH-CARRIER-FREQUENCY DIFFRACTIVE ELEMENTS

Complex-amplitude modulation is necessary if we wish to suppress the n oise that surrounds the signal in diffractive optics. This is desirabl e in, e.g., space-invariant optical interconnection. We present a math ematical scheme to synthesize high-carrier-frequency diffractive eleme nts that perform phase and amplitude modulation of the first carrier-g rating order without the use of absorption. The amplitude information is encoded in grating-depth variations and in the phase information in pulse-position modulation. Use of rigorous diffraction theory in the design of the local grating structure ensures virtually noise-free rec onstruction with efficiencies that are significantly higher than the V alues one typically obtains, e.g., by conventional holographic recordi ng. (C) 1996 Optical Society of America