Filters and wavefront dividing beamsplitters for the near and mid infrared produced by micromachining techniques

摘要

Band pass filters for the far infrared have been produced by etching crosses into metal films on Mylar substrates. Unsupported thin cross shaped filters for the far infrared have been produced by etching crosses into 4 microns thick nickel foils. These authors studied the dependence of the wavelength of peak transmission, bandwidth, and percentage of peak transmission on the shape of the crosses. Very accurately shaped crosses in thick metals for the mid infrared have been produced using LIGA. These filters showed a strong side peak and transmission in the 70% to 80% range. Theoretical calculations by Compton et al for thin filters predict such a side peak, depending on the shape of the cross, and 100% transmission. To obtain maximum transmission for band pass filters, a tripod shape was used instead of the cross. These filters showed 100% transmission and the side peak for a thickness of 10.5 microns. The side peak is getting smaller for thinner filters.