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. A method comprising:
providing an array of photodetectors spaced apart along a length dimension of an optical filter,
the array of photodetectors being responsive to different wavelengths of light; and depositing, on the array of photodetectors, a bandpass filter and a blocking filter,
the bandpass filter comprising first and second layers comprising first and second materials, respectively, and having a first laterally varying thicknesses for providing a laterally variable transmission wavelength, andthe blocking filter comprising third and fourth layers comprising third and fourth materials, respectively, and having a second laterally varying thicknesses, coordinated with the first laterally varying thicknesses of the first and second layers, for blocking wavelengths, within a wavelength range, that are larger or smaller than the laterally variable transmission wavelength,
the bandpass filter further comprising 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.