Optical device using laterally-shiftable diffraction gratings
AssigneesToyota Motor Engineering & Manufacturing North America, Inc., The Trustess of the University of Pennsylvania
InventorsHideo Iizuka, Nader Engheta
Life of this patent
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Abstract
A double-sided grating divider acts as a light switch where the upper and lower grating dividers are arranged to accommodate a relative lateral shift therebetween of about one-fourth of the period of the diffraction grating elements and where the critical refraction angles of the grating dividers are more than about 43.6°. Lateral shift may be achieved by various devices including MEMS and metal couplers having a known/calibrated thermal coefficient of expansion over a temperature range of interest.
Claims20
An optical device responsive to incident light having a component of wavelength, λ, the optical device comprising:
- first and second substantially identical diffraction grating dividers each having a distributed plurality of grating elements having a predetermined, regular geometry and being formed of a first material contacting a medium and disposed at a surface of a substrate;
- said first and second diffraction grating dividers being arranged in mutually inverted but spaced apart and substantially aligned relationship;
- and
- means for varying lateral alignment of the first and second diffraction grating dividers relative to one another to vary a degree to which incident light is transmitted therethrough,
- wherein the first material has a refractive index greater than a refractive index of the substrate, and the refractive index of the substrate is greater than a refractive index of the medium, at wavelength, λ.
A light valve responsive to incident light having a component of wavelength, λ, the light valve comprising:
- first and second substantially identical diffraction grating dividers each made up of a distributed plurality of grating elements disposed at a surface of a substrate, the grating elements having predetermined, regular geometries and formed of a first material, the grating elements and substrate contacting a medium, an interface of the substrate and the medium having a critical angle, wherein the diffraction grating dividers diffract the component of light with a diffraction angle that exceeds the critical angle;
- said first and second diffraction grating dividers being arranged in mutually inverted relationship;
- a side of the first diffraction grating divider providing an input to incident light, and a side of the second diffraction grating divider providing an output to transmitted light;
- and
- the grating elements of the first and second diffraction grating dividers being arranged to permit variations in lateral alignment which variations vary transmission of light through the light valve;
- wherein the first material has a refractive index greater than a refractive index of the substrate, and the refractive index of the substrate is greater than a refractive index of the medium, at wavelength, λ.
A window that is variably transmissive toward a component of incident light having wavelength, λ, the window comprising:
- first and second diffraction grating dividers each made up of a distributed plurality of grating elements disposed at a surface of a substrate, the grating elements having regular geometries and formed of a first material, the grating elements and substrate contacting a medium, an interface of the substrate and the medium having a critical angle, wherein the diffraction grating dividers diffract the component of light with a diffraction angle that exceeds the critical angle;
- said first and second diffraction grating dividers being arranged in mutually inverted, substantially laterally aligned, spaced-apart relationship with an interface substance having a refractive index of about 1 therebetween;
- a first side of the first diffraction grating divider providing an input surface to incident light, a first side of the second diffraction grating divider providing an output surface for light transmissively diffracted by the first diffraction grating divider;
- and
- means for varying lateral alignment between the elements of first and second grating dividers thereby to vary transmission of the component of incident light through the window;
- wherein the first material has a refractive index greater than a refractive index of the substrate, and the refractive index of the substrate is greater than a refractive index of the medium, at wavelength, λ.
A light valve responsive to a component of incident light having wavelength, λ, the light valve comprising:
- first and second diffraction gratings, each having periodic grating elements with a first refractive index toward the component of incident light disposed at a surface of a substrate having a second refractive index toward the component of incident light;
- a liquid medium;
- said first and second diffraction gratings being arranged in opposed and aligned relationship with said liquid medium therebetween;
- and
- means for changing alignment between said first and second diffraction gratings thereby to vary transmission of incident polarized light through the valve,
- wherein the first refractive index is greater than the second refractive index.
Dependencies are inferred from the claim text.