Fabrication of a 33-layer optical reflection filter with stepwise graded refractive index profiles

A novel optical multilayer filter characterized by symmetrically stepwise g raded refractive index profiles and high optical performance was designed. This 33-layer TiO2-SiO2 filter was fabricated by helicon plasma sputtering. The prepared filter exhibited a sharp cutoff reflection band around the ce ntral wavelength of 1340 nm and wide pass regions with high transmittance. These results correspond well with calculated estimations. Symmetrically st epwise graded refractive index profiles were demonstrated to effectively co ntribute to suppression of the sidelobes and to be potentially applicable i n the design of other filters.