Stepwise graded refractive-index profiles for design of a narrow-bandpass filter.

A combination of stepwise graded refractive-index profiles and a cavity structure is used for designing narrow-bandpass filters of TiO(2)/SiO(2) multilayer films upon BK7 glass substrates. Symmetrical profiles of stepwise graded refractive indices result in high transmittance of passbands for the designed filters. The bandwidth of the narrow-bandpass filter is controlled by adjustment of parameters such as the thickness and the number of layers in the multilayer stack. This design is proposed as a new and simple method for coating synthesis of optical filters.