Improved linear response to UV exposure and its interpretation of SiO2/TiO2hybrid sol-gel glass

A negative-tone inorganic-organic hybrid SiO2/TiO2 sol-gel glass is applied to make blazed gratings using a high-energy beam-sensitive (HEBS) grey-scale mask with ultraviolet (UV) exposure. To improve the sol-gel material's linear response to the optical densities (ODs) of the HEBS grey mask, a new recipe of sol-gel synthesis is investigated to offer good linear UV response to ODs of the HEBS mask. The calibration results show that the linearity of the UV response versus ODs is significantly improved for the whole OD range between 0.12 and 1.12. The sol-gel film thickness has been increased to 3µm so that it enables us to realize 2π phase difference for diffractive optical elements in the visible and near IR wavelength range. It is seen that the transmittance curve has an UV shift, which played an important role to improve the properties of the sol-gel material.