Design and Fabrication of Binary Microlenses with Quartz Substrate
Most of binary optical elements are used as microlens array or special lenses. However, the efficiency of binary optical elements is one of the most important considerations in their design and applications. To achieve good performance, usually it is desirable to maximize the efficiency of the diffractive structure. These elements fabricated with VLSI techniques normally have very high theoretical diffraction efficiencies, based on scalar diffraction theory. However, the scalar theory is based on several assumptions, which are invalid in some cases. The minimum feature size is also limited by the current fabrication technique, that reduces the achievable diffraction efficiency. In this thesis the diffractive micro-lens and its design were discussed and analyzed with the conventional scalar diffraction theory. A new design concept was proposed, in which the fabrication limitation is consided in the design and possible best diffraction efficiency could be gotten. Based on this idea, a six-level microlens was fabricated with quartz (fused silica) substrate. A conventional eight-level microlens was also fabricated. The spot sizes, 57μm for six-level and 59μm for eight-level were measured. But the method for the measurement of diffraction efficiency needs to be improved in feature.
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