Micro-Resonant Optical Filters With Reduced Angle Sensitivity
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Solution Overview
Problem
Conventional optical and infrared sensing systems, such as multispectral and hyperspectral sensors, are limited by their size, complexity, fragility, and cost due to the use of dispersive elements like gratings, which require additional optical elements and are sensitive to angle of incidence, leading to overlapping wavelength components and increased computational burden.
Innovation Solution
A device with an encapsulated layer of micro-resonant elements and a highly reflective filtering structure, featuring a stopband, that minimizes the dependence of the center wavelength on the angle of incidence, allowing for a narrow passband transmission with reduced size and complexity, suitable for miniaturization and use on small platforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional dispersive elements (gratings) are used for spectral discrimination, then spectral separation capability is achieved, but device size and complexity increase due to required collimating lenses and additional optical elements
Solution Approach 1:
The patent combines multiple optical functions (dispersion, collimation, and spectral filtering) into a single integrated photonic circuit chip. The waveguide structure integrates the dispersive element and collimating function together, eliminating the need for separate collimating lenses and reducing the number of optical components while maintaining spectral discrimination capability
Solution Approach 2:
The patent replaces conventional mechanical/optical dispersive elements (gratings with lenses) with a photonic circuit implementation using waveguides and modulators. This substitution transitions from a mechanical/optical system to an integrated photonic system, reducing device complexity and enabling miniaturization
2Measurement precision
If conventional dispersive elements (gratings) are used for spectral discrimination, then spectral separation is achieved, but the system requires additional optical elements (collimating lenses, slits, imaging lenses) that increase size
Solution Approach 1:
The patent merges the dispersive element, collimating lens, and spectral filter functions into a single integrated photonic circuit chip. The waveguide structure provides both dispersion and collimation in one component, eliminating the need for multiple separate optical elements and significantly reducing device volume
Solution Approach 2:
The patent implements a nested structure where the dispersive waveguide is integrated within the photonic circuit chip, and the spectral filtering function is embedded within the same chip structure. This nesting of multiple functions within a single chip volume dramatically reduces the overall device size compared to conventional systems
3Measurement precision
If conventional dispersive elements (gratings) are used, then spectral separation is achieved, but sensitivity to angle of incidence causes wavelength components to overlap and ruins spectral discrimination
Solution Approach 1:
The patent replaces the conventional grating-based dispersive element with a photonic circuit implementation using waveguides. The waveguide structure provides angle-insensitive dispersion through its guided mode properties, eliminating the sensitivity to angle of incidence that plagues conventional grating systems and ensuring reliable spectral discrimination
4Loss of information
If conventional dispersive elements produce continuum of wavelength components, then complete spectral information is obtained, but computational burden increases for processing and discarding signals from undesired spectral channels
Solution Approach 1:
The patent extracts and isolates only the specific spectral channels of interest using integrated spectral filters within the photonic circuit. Instead of producing a continuum of all wavelength components, the system selectively transmits only the desired spectral bands, eliminating the need to process and discard signals from undesired channels and reducing computational burden
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device achieves high-precision spectral filtering with reduced angle of incidence dependence, enabling miniaturization and reduced computational requirements, suitable for small aerial and space-based platforms.
Implementation Method 1
an array of micro-resonant elements arranged spatially distinct from each other in a plane of the device... Each micro-resonant element is formed of a first material... The array of micro-resonant elements is configured to transmit a passband of incident radiation centered around a center wavelength, wherein the center wavelength falls within the stopband of the highly reflective filtering structure, and to minimize a dependence of the center wavelength on an angle of incidence
Implementation Method 2
a highly reflective filtering structure including at least one of an upper structure positioned a first distance above the encapsulated layer and a lower structure positioned a second distance below the encapsulated layer, wherein the highly reflective filtering structure is characterized by a stopband
Implementation Method 3
Devices with reduced angle-of-incidence dependence... narrow bandwidth filters for optical and infrared sensing... high-precision spectral filtering with reduced angle of incidence dependence
Data Source
AI summary
A device, or a pixel of a device, for filtering of incident radiation includes an array of discrete micro-resonant elements in an encapsulated layer, the encapsulating material having a lower index of refraction than the micro-resonant elements. A highly reflective filtering structure is positioned a first distance above the encapsulated layer and/or a second distance below the encapsulated layer, and is characterized by a stopband. The array of discrete micro-resonant elements is configured to transmit a passband of incident radiation centered around a center wavelength that falls within the stopband of the highly reflective filtering structure, and to minimize a dependence of the center wavelength on an angle of incidence (AoI) of the incident radiation. A pixelated device includes a plurality of pixels, each having an array of the discrete micro-resonant elements tuned to transmit a different passband having a different center wavelength, while minimizing dependence on AoI.