Rugate filters prepared by rapidly alternating deposition

A methodology for the fabrication of composite (Nb₂O₅)_1-x(SiO₂)_x thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating deposition technology. The optical properties of the composite films varying with the composition of the material are studied in detail. Refractive indices between 1.50 and 2.14 can be realized in our coating system. Two designed rugate filters with a reflection band at the wavelength of 532 nm are fabricated using an automatic deposition process. The microstructure of the rugate filter is investigated by using scanning electron microscopy. The calculated and the measured transmittance spectra are in good agreement with each other. The causes of the slight differences between them are also analysed.