Variable optical filter and a wavelength-selective sensor based thereon

摘要

A variable optical filter is disclosed including a bandpass filter and a blocking filter. The bandpass filter includes a stack of alternating first and second layers, and the blocking filter includes a stack of alternating third and fourth layers. The first, second and fourth materials each comprise different materials, so that a refractive index of the first material is smaller than a refractive index of the second material, which is smaller than a refractive index of the fourth material; while an absorption coefficient of the second material is smaller than an absorption coefficient of the fourth material. The materials can be selected to ensure high index contrast in the blocking filter and low optical losses in the bandpass filter. The first to fourth layers can be deposited directly on a photodetector array.

主权项

1. An optical filter having a laterally variable transmission wavelength within a wavelength range, the optical filter comprising:
a bandpass filter comprising a stack of alternating first and second layers comprising first and second materials, respectively, and having laterally varying thicknesses for providing the laterally variable transmission wavelength; a blocking filter comprising a stack of alternating third and fourth layers, comprising third and fourth materials, respectively, and having laterally varying thicknesses coordinated with the laterally varying thicknesses of the first and second dielectric layers, for blocking wavelengths within the wavelength range that are larger or smaller than the laterally variable transmission wavelength; wherein the first, second and fourth materials each comprise different materials, so that a refractive index of the first material is smaller than a refractive index of the second material, the refractive index of the second material is smaller than a refractive index of the fourth material, and an absorption coefficient of the second material is smaller than an absorption coefficient of the fourth material; and wherein the bandpass filter further comprises at least one fifth layer comprising the fourth material and disposed in an area of a local minimum of a standing optical wave inside the bandpass filter, whereby a blocking wavelength region of the bandpass filter is broadened, and a thickness of the bandpass filter is reduced.