Ion beam sputtering mixture films with tailored refractive indices

•Calculation revealed that the calibration curve should be a Boltzmann expression.•Experimental refractive indices should be used to gain the calibration curve.•Refractive indices could be precisely tailored by use of the calibration curve.•Rugate filters were fabricated using calibration curve at 500 nm and 1000 nm.•FIB was used to characterize the rugate filter profile.

Material with tailorable optical constants was favorable in coating design. The Ion Beam Sputtering technology was used to produce mixture films with tailored refractive indices by utilizing a movable target composed of two materials. A model was established to study the calibration curve representing different refractive indices at different target positions. Boltzmann expression was found to well fit the calibration curve with several parameters. Rugate filters composed of over 100 different mixture layers with tailored refractive indices were fabricated and studied.