Optical filter absorbing part of optical signals

摘要

The absorbed signals have a medium wavelength, and the filter limits the intensity of the passing light and contains a substrate (1), a dielectric block (4) with a high refractive index, a metal film (3), and a dielectric block (2) with a low refraction index. The high refractive index dielectric block, the metal film, and the low refractive index dielectric block are deposited on the substrate in this order in the direction of impinging light. The metal film is of metal with a refraction index of at least 1 for the medium wavelength. Preferably the two dielectric blocks are formed each by a thin, dielectric, single layer.