Advanced Holographic Phase Nulls Suitable for EUV Quality Optical Testing

A number of future space sciences missions require optical surfaces that are accurate to nanometer and sub-nanometer levels. These applications include large aperture systems such as the Terrestrial Planet Finder (TPF) chronograph, where mid-spatial frequency surface error content is restricted to 2 nm RMS, and EUV wavelength applications, like SHARPI, where full aperture surface errors need to be reduced to the single nanometer level. In most cases these optical systems require components which are generalized aspheres, with no simple point tests. Computer Generated Holographic (CGH) null optics are typically applied to test these optical surfaces. As the quality requirements placed upon these optics gets tighter, the precision associated with CGH manufacturing needs to improve as well. CGH's are produced using laser or e-beam based pattern generation tools which were originally developed for photomask generation in the lithography industry. Tinsley Laboratories proposes to develop CGH improvements in the area of substrate preparation and pattern placement errors. Tinsley, an industry leader in the application of CGH testing approaches, will work closely with Diffraction International, Inc. the industry leader in the area of CGH manufacturing. Tinsley's experience with the application of CGH tools, and our state-of-the-art Computer Controlled Optical Surfacing (CCOS) manufacturing processes, make us well suited to address issues related to implementation and substrate preparation. Diffraction International will provide support with regard to techniques which can provide improvements in the pattern placement area, and the evaluation of alternative manufacturing platforms that might be utilized to provide higher quality diffractive nulls. Our overall goal is to provide a 10x reduction in the residual error associated with current state-of-the-technology CGH null optics.