Ultraviolet filter for ring laser gyroscope mirrors

A multilayer mirror comprises a reflector section including a plurality of alternating layers of a high index material and a low index material, and a filter section over the reflector section. The filter section comprises a first filter layer including a low index material on a layer of high index material of the reflector section; a second filter layer on the first filter layer, the second filter layer comprising a high index material that is different than the high index material in the reflector section; and a third filter layer on the second filter layer, the third filter layer comprising a low index material. Each filter layer has an optical thickness greater than or equal to the optical thickness of each layer of the alternating layers. The filter section substantially blocks ultraviolet (UV) energy, thereby preventing UV energy from substantially impinging on the high index material of the reflector section.