Shared Aperture Diffractive Optical Element (ShADOE) Multiplexed Telescope

The Shared Aperture Diffractive Optical Element (ShADOE) is an Advanced Component Technology program to demonstrate the feasibility of combining several holographic optical elements (HOEs) into a single optic for use as the primary optic of a scanning telescope. The HOEs diffract the beam at a fixed elevation angle, nominally 30 to 55 degrees, but with the azimuthal pointing direction of each individual HOE rotated by 30 or more degrees with respect to the others. Several HOEs are multiplexed into a single ShADOE. This construction is equivalent to having multiple telescope primary lenses all in one optic. This technology allows us to do the equivalent of scanning a large aperture telescope between widely separated fields of view without physically moving or scanning the primary optic. A powered Holographic Corrector Plate is used to collimate the output and correct for wavefront errors induced by the primary HOE, forming an afocal, near diffraction limited holographic telescope. We have observed wavefront errors of only a few times the diffraction limit at 355 nm with a 40-cm diameter SHADOE system.