A method of manufacturing an optical element (705), such as a metal-dielectric filter, is disclosed. The method comprises a step of deposition of a layer of metallic material (170). The method comprises a step of deposition of an encapsulating layer of dielectric material (190), such that the layer of metallic material (170) is encapsulated between the encapsulating layer of dielectric material (190) and the substrate (110) or a preceding layer of dielectric material (105). Deposition of the encapsulating layer of dielectric material (190) is more isotropic than deposition of the layer of metallic material (170). Also disclosed is an optical element (705) manufactured according to the method.