A new organic-inorganic hybrid material, that created photoinduced reduction of refractive index as well as volume contraction, has been prepared using a sol-gel method. Whereas previous photosensitive materials show the photoinduced increase in refractive index, this hybrid material creates the significant decrease in refractive index using the decomposition of methacrylate on light irradiation. Moreover, this hybrid material is patternable without any developing steps such as wet etching and thermal curing after light exposure. The reduction of refractive index measured with a prism coupler was about 0.045, particularly exhibiting a low refractive index value of 1.385. We investigate the structural change of the hybrid material upon light irradiation by FT-IR, UV spectrophotometer, and energy dispersive X-ray spectroscopy (EDS) and the surface roughness change by AFM. We also carry out direct imprinting of the organic-inorganic hybrid material without any further steps (wet etching, thermal curing, or UV fixing), using the volume contraction upon light irradiation.
