Although many studies on graded index (GRIN) lenses have been reported over the past several years, it is extremely difficult to find reports that have used polymer GRIN lenses in an atmosphere involving a large temperature change, which is mainly because of their lack of thermal stability. In this study, we propose a new method of fabricating organic-inorganic microcomposite cylindrical GRIN lenses with high thermal stability. This method is based on the spontaneous frontal polymerization (SFP) technique and diffusion of two organic materials with different refractive indices into an inorganic wet-gel. The refractive index profile of the GRIN lens is made by this diffusive process. We are able to determine the relationship between the refractive index profile and the diffusion time using our original refractive index profile simulation, based on the diffusion equation. The obtained microcomposite cylindrical GRIN lenses are not only thermally stable but also have a controlled refractive index profile, due to their inorganic matrix. The lenses are also highly transparentan essential factor. The SFP technique also enabled high reproducibility of microcomposite cylindrical GRIN lenses with smooth periphery in this study, indicating the high potential of this process for practical application.
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