DARK BEAMS WITH A CONSTANT NOTCH

Dark beams are wave fields carrying information in dark regions. mie e xperimentally demonstrate dark beams that maintain a constant notch sh ape and size along a predetermined domain in free space. The energy is concentrated around the dark region with negligible sidelobes. These beams are generated with low-information-content phase-only diffractiv e elements in an on-axis configuration. (C) 1996 Optical Society of Am erica