Abstract: An optical filter uses a multi-layer, stack of alternating dielectric layers (16, 18) of different refractive indices, a dielectric spacer layer (20) and metal layer (21), to achieve a narrow overall absorption bandwidth, with high reflectance upon either side. A tunable (optical) filter variant uses a dielectric stack and spacer coating of spatially-varying thickness, that is a coating of depth varying, say linearly and/or circularly, according to position across an absorbent layer or substrate, whereby, at different positions on the surface, a different wavelength is absorbed. A tunable laser (35) uses opposed tunable filters (26, 28) bounding a lasing medium (38), such as CO2 gas, for selective variable stimulated emission of radiation (39).

Abstract: A method of vacuum depositing a layer or layers on a substrate includes controlling thickness distribution of the layer or layers over the substrate by a three-dimensional mask (64) located between the substrate 48 and a vapor source (56). In one example a circular mask (64R) is divided by radially-extending spaced-apart walls (90) dividing the mask into radially-extending apertures (98) for allowing passage of gaseous coating material through the mask from a source to the substrate. The mask and substrate are rotated with respect to the source. The vapor transmission of the apertures is directly related to the height and spacing of the walls. The height and/or angular-spacing of the walls is varied over the mask for spatially varying thickness of the layer or layers over the substrate.

Abstract: A method of vacuum depositing a layer or layers on a substrate includes controlling thickness distribution of the layer or layers over the substrate by a three-dimensional mask (64) located between the substrate 48 and a vapor source (56). A plurality of conduits (52) extends through the mask from one side to the other for allowing passage of gaseous coating material from a source to the substrate. The length of the conduits is inversely related to the throughput of the conduits for gaseous coating material, and thus the amount of gaseous coating material transmitted by the conduits. The conduit lengths are graded over the mask to provide corresponding gradation of a deposited layer.