Abstract
Photosensitive sol-gel hybrid (SGH) materials exhibited the peculiar photoinduced migration behavior of unreacted molecules from unexposed areas to exposed areas by selective UV exposure. Using the photoinduced migration mechanism of the photosensitive SGH materials, the microlens array (MLA) with a smooth surface was directly photofabricated, and the focal length was controlled by changing the photoinduced migration parameters. The higher photoactive monomer content and the thicker film creating a higher curvature produced a smaller focal length of the MLA. Thus, a simple fabrication and easy control of the focal length can be applicable to a fabrication of an efficient MLA.
Highlights
Microlens arrays (MLA) are important components for beam dispersion and in the conversion for an application of an optical interconnection and of signal processing in compact and complicated optical data storage, sensing, and imaging systems [1,2,3]
MLAs are generally fabricated by methods such as lithography, etching techniques, re-flowing photoresist, isotropic etching substrate, LIGA process, ink-jet, etc. [6,7,8,9,10]
Since the photosensitive sol-gel hybrid (SGH) materials show photoinduced simultaneous change both in refractive index and volume, a more precise control of the focal length is possible that allows for the fabrication of a high efficiency MLA
Summary
Microlens arrays (MLA) are important components for beam dispersion and in the conversion for an application of an optical interconnection and of signal processing in compact and complicated optical data storage, sensing, and imaging systems [1,2,3]. This is intimately related to the transport and content of the photoactive molecules, which in turn depends on various parameters, including the UV dose, film composition, film thickness, and the exposed area size All of these parameters are readily controlled, allowing considerable freedom in the design and the surface relief structuring of the directly photofabricated patterns with various sizes and shapes. Since the photosensitive SGH materials show photoinduced simultaneous change both in refractive index and volume, a more precise control of the focal length is possible that allows for the fabrication of a high efficiency MLA. It was demonstrated that the curvature of the directly photofabricated MLA is sensitive to the photoinduced migration parameters of the photoactive molecule concentration and film thickness for its focal length to be controlled
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