Optical thin film, optical element, and optical system

An optical thin film that is provided on a substrate, the film comprising, in order, from the substrate side:

• an interlayer;
• a silver-containing metal layer that contains silver;
• and
• a dielectric layer,
• wherein an anchor region including an oxide of an anchor metal is provided in an interface region of the silver-containing metal layer on a side close to the interlayer,
• a cap region including an oxide of the anchor metal is provided in an interface region of the silver-containing metal layer on a side close to the dielectric layer,
• a film thickness of the silver-containing metal layer including the anchor region and the cap region is 6 nm or less,
• the silver-containing metal layer contains a high standard electrode potential metal which is a metal having a standard electrode potential higher than that of silver, and a peak position of a concentration distribution of the high standard electrode potential metal in a film thickness direction of the silver-containing metal layer is positioned closer to the interlayer than a peak position of a silver concentration distribution.