Abstract: Negative surface relief diffractive optical elements (218) are supported or formed at interior surfaces of injection molding molds (200, 916, 1002) for wireless communication device housing parts (502). Such injection molding molds are used to making housing parts that include integrally molded surface relief diffractive optical elements (504) e.g., holograms. Such diffractive optical elements can be used to convey information or for decorative effects. The negative surface relief holograms can be mechanically mounted or formed on the interior surfaces by exposing a resist on the interior surfaces to a holographic light field or a succession of laser interference patterns, and there after developing and using the resist as an etch mask.