Optical filter including a sub-wavelength periodic structure and method of making

An apparatus for filtering incident light comprising a plurality of deposited layers, with at least two layers forming a resonant cavity and another of the layers being located within the resonant cavity and including at least one sub-wavelength periodic structure for defining, at least in part, a predetermined center wavelength for transmission of a component of the incident light through the resonant cavity by providing an effective index of refraction for the dielectric layer that is different from the index of refraction of a material forming the dielectric layer within the resonant cavity.

An optical filter comprising:

• a layered structure which includes an optical cavity formed by a pair of planar mirrors;
• and
• a sub-wavelength periodic structure located within the optical cavity for defining, at least in part, a predetermined center wavelength for transmission of light through the layered structure in a direction substantially perpendicular to a surface thereof by providing an effective index of refraction within the optical cavity that is different from the index of refraction of a dielectric material forming the sub-wavelength periodic structure.

An optical filter for transmitting light within at least one wavelength band centered at a predetermined wavelength, comprising;

• a pair of reflecting mirrors arranged to form an optical cavity;
• and
• a dielectric layer formed on a surface of one of the mirrors within the optical cavity and having in at least one portion thereof an effective optical thickness substantially equal to an integer multiple of one-half the predetermined wavelength, with the effective optical thickness being determined, at least in part, by a sub-wavelength periodic structure formed within the dielectric layer and having an effective index of refraction different from the index of refraction of a material forming the dielectric layer.

An optical filter comprising:

• first and second stack mirrors having surfaces in contact to form an optical cavity, with each stack mirror further comprising a plurality of alternating high-refractive-index layers and low-refractive-index layers, and with at least one of the stack mirrors having a sub-wavelength periodic structure formed proximate to the surface thereof for providing an effective index of refraction different from the index of refraction of a material forming the sub-wavelength periodic structure, thereby defining a predetermined wavelength band for transmission of light.