Control of an ion beam for milling optical surfaces is a nontrivial problem in two-dimensional deconvolution. The ion milling operation is performed by moving an ion beam gun through a grid of points over the surface of an optical workpiece. The control problem is to determine the amount of time to dwell at each point in the grid to obtain a desired surface profile.This research treats the problem in linear algebra terms. The required dwell times are the solution to a large, sparse system of linear equations. Traditional factorization methods such as Gaussian elimination cannot be used because the linear equations are severely ill conditioned. Theoretically, a least-squares solution to this problem exists. Practical approaches to finding a minimal least-squares solution are discussed.

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Ion beam milling is an emerging advanced optical fabrication technology capable of deterministic figuring of optical surfaces. Much of the work in ion milling to date has emphasized figuring of glass-like materials, such as fused silica, which do not significantly roughen during ion milling. However, for ion milling to reach its full potential as an advanced optical fabrication technique it must be applicable to a broad range of materials of interest in optical fabrication including polycrystalline metals, semiconductors, and ceramics. In order to assess the feasibility of ion milling, the effect of ion dose on roughness evolution was investigated for a variety of materials including: silicon, germanium, sapphire, silicon carbide, fused silica, aluminum, and copper. Single crystal silicon, germanium and sapphire as well as polycrystalline CVD silicon carbide did not significantly roughen during ion milling. The roughness evolution of aluminum, copper and gold thin films were also studied; fine grained gold films were found to remain smooth during ion milling.

.It is well known that the work function of metals de-es when they are pIaced in a nonpolar liquid. A similar decrease occurs when the metal is placed into contact with a semiconductor forming a Schottky barrier. We report on a new method for detecting photons using the stress caused by pho~o-electrons emitted tim a metal film surfme in contact with a semiconductor microstructure. The photoelectrons diffuse into the microsticture and produce an electronic stress. The photon detection results fiorn the measurement of the photo-induced bending of the microstructure. Internal photoemission has been used in the past to detect photons, however, in those cases the detection was accomplished by measuring the current due to photoelectrons and not due toelectronic stress. Small changes in position (displacement) of microstructure are routineIy measured in atomic force microscop y (AFlvl) where atomic imaging of surfaces relies on the measurement of small changes (< 10"'m) in the bending of microcantilevers. In the present work we studied the photon response of Si microcantiIevers coated with a thin film of Pt. The Si microcantiievers were 500 nm tii~and had a 30 mn layer of Pt. Photons with sufficient energies produce electrons from the platinum-silicon interfhce which diffise into the Si and produce an electronic stress. Since the excess charge carriers cause the Si microcantilever to conmct in length but not the F%layer, the bimaterial microcantilever bends. In our present stdies we used the optical detection technique to measure the photometric response of Pt-Si microcantikwers as a function of photon energy. The charge carriers responsible for the photo-induced stress in Si, were produced via internal photoemission using a diode laser with wavelength A =1550 nm.

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