Optical filter including cubic hafnium oxide crystal, method for producing same, and sterilization device including optical filter

Abstract

There is provided an optical filter capable of effectively transmitting ultraviolet light in a wavelength range from 220 nm to 225 nm while suppressing the transmission of ultraviolet light in a wavelength range from 240 nm to 320 nm. An optical filterincludes a transparent substrateand a dielectric multilayer filmprovided on the transparent substrateand containing hafnium oxide. A minimum value of spectral transmittance in a wavelength range from 220 nm to 225 nm is 50% or more with an incident angle of 0 degrees, and a maximum value of spectral transmittance in a wavelength range from 240 nm to 320 nm is 5% or less with an incident angle of 0 degrees.