An example article may include an optical filter and a multilayer stack adjacent the optical filter. The multilayer stack may include a plurality of layers. Each respective layer of the plurality layers may define a respective window edge of a plurality of window edges. The plurality of window edges may define an optical window configured to transmit light through the optical filter. At least a first respective window edge of the plurality of window edges may be stepped relative to at least a second respective window edge of the plurality of window edges.