Polysilane Films for Optical Devices

FIGURE 30. Structure of liquid crystal cells. (Reprinted from Ref. 131.) 

An array of 10- i,m microlenses was fabricated from the adhesion of an aminated silicasol on a poly[methyl(phenyl)silane-co-methyl(3,3,3-tri-fluoropropyl)silane] (CF3PMPS) film patterned by UV light irradiation.132 By soaking the UV-patterned polysilane film into the sol-gel solution, a convex xerogel layer adhered only to the UV-exposed poly silane, which was cured to form a glass that functioned as a condensing lens. 

FIGURE 31. The refractive index variation in the PMPS film by UY-light irradiation using different light sources (a) excimer lamp (308 nm) and (b) mercury-arc lamp (185, 254, 303 nm). (Reprinted from Ref. 134.) 

When the excimer lamp of 308 nm is used for the irradiation light source, the refractive index lowers from 1.70 to 1.63. With the mercury-arc lamp the refractive index lowers to 1.58. The larger reduction of the refractive index with the shorter wavelength light derives from the elimination of the side-chain phenyl group. 

UV light induced refractive index change has been observed in organic polysilane (PS)-silica and PS-titania hybrid thin films prepared by the sol-gel method.135 The magnitude of the refractive index change was found to be 0.16 for 50 wt % PS-silica and 0.18 for 50 wt % PS-titania hybrid thin films. It was demonstrated that the refractive index change of the hybrid thin films is due to the photodecomposition of PS. These findings indicate potential usefulness of the hybrid thin films as optical devices with refractive index modulated structures. 

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