SBIR-STTR Award

Current shared aperture diffractive optical elements (SHADOE) have intrinsic residual wavefront errors on the order of 20 waves which limits the angular resolution of the LIDAR application to a range between 150 and 400 micro-radians. It is possible to reduce these aberrations by constructing a secondary holographic correction plate using the aberrated wave from the SHADOE as one of the two construction waves. The other construction wave is either a collimated wave or an f#2 focused wave. All five overlapping apertures require individually constructed plates. This method of correction requires the use of the final playback wavelength for construction and so is useful for 532 and 355nm but not for 1064 nm. Computed diffractive optics can be used for 1064 nm using measured aberrations at the same wavelength. This proposal deals just with fabrication and test of the 355 nm LIDAR applications for which an entirely optical recording set up is adequate. Correction plates in the 2 inch diameter range are proposed with likely reduction in angular spread to under 50 micro-radians, which will greatly improve the signal to noise numbers in a LIDAR application.

Current shared aperture diffractive optical elements (ShADOE) have intrinsic residual wavefront errors on the order of 50 waves which limits the angular resolution of the LIDAR application to about 300 micro-radians. We have reduced these aberrations by constructing a secondary holographic correction plate using the aberrated wave from the ShADOE as one of the two construction waves. The other construction wave was collimated. All six overlapping apertures require individually constructed plates, we delivered only 2 thus far. This method of correction requires the use of the final playback wavelength for construction and so is useful for 532 and 355nm but not for 2054 nm. Computed diffractive optics can be used for 2054 nm using measured aberrations at the same wavelength. This proposal deals just with a continuation of fabrication and test of the 2 inch 355 nm holographic correction plates (HCP) to bring resolution well under 50 micro radians. Secondarily we propose to make and measure a small 2054 nm ShaDOE and demonstrate a digitally mastered HCP that will approach diffraction limited performance as required at that wavelength.