Photonic Crystal Filter for Broadband Angular Selectivity
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Solution Overview
Problem
Current technologies face challenges in achieving broadband angular selectivity of electromagnetic waves, particularly in the optical regime, for applications such as solar energy conversion and privacy protection, due to difficulties in realizing metallic extraordinary transmission and geometrical optics at the micrometer scale.
Innovation Solution
The development of photonic crystal structures with multilayer cells comprising isotropic and anisotropic sheets, aligned along the surface normal direction, which define a Brewster angle and create bandgaps that cover a continuous spectral region, allowing for the transmission of radiation at a specific incidence angle while reflecting it at other angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If metallic extraordinary transmission is used to achieve angular selectivity, then transmission at specific angles is improved, but manufacturing complexity and difficulty increase significantly
Solution Approach 1:
The patent changes the fundamental parameters of the filter structure by using photonic crystal structures with specific periodicities and dielectric materials instead of metallic structures. This allows achieving angular selectivity through photonic bandgaps and Brewster angle effects rather than relying on difficult-to-manufacture metallic extraordinary transmission structures
Solution Approach 2:
The patent employs composite photonic crystal structures consisting of multiple layers with different dielectric permittivities (first dielectric layer and second dielectric layer) to achieve the desired angular selectivity. These composite structures provide both the angular filtering capability and manufacturability
2Adaptability or versatility
If broadband angular selectivity is achieved across a continuous spectral region, then spectral coverage is improved, but device complexity increases
Solution Approach 1:
The patent divides the broadband filtering requirement into multiple discrete photonic crystal structures, each with a specific periodicity that defines a particular bandgap. By combining multiple segmented structures with different periodicities, the system achieves continuous spectral coverage from about 50 nm to about 100 mm without requiring a single complex structure
Solution Approach 2:
Each photonic crystal structure in the plurality serves multiple functions: it provides angular selectivity through Brewster angle effects, creates photonic bandgaps for spectral filtering, and contributes to the overall broadband coverage. This multi-functionality reduces the need for separate components
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
This solution enables broadband angular selectivity, improving the efficiency of solar energy conversion and enhancing signal-to-noise ratios in detectors, while also providing privacy protection by selectively transmitting radiation at specific angles.
Implementation Method 1
Each photonic crystal structure in the plurality of photonic crystal structures defines a respective bandgap, and the respective bandgaps of the plurality of photonic crystal structures, taken together, cover a continuous spectral region of about 50 nm to about 100 mm
Implementation Method 2
The first layer and the second layer define a Brewster angle substantially equal to the predetermined incidence angle based on the first dielectric permittivity and the second permittivity
Data Source
AI summary
A filter to transmit incident radiation at a predetermined incidence angle includes a plurality of photonic crystal structures disposed substantially along a surface normal direction of the filter. The photonic crystal structure includes a multilayer cell that comprises a first layer having a first dielectric permittivity, and a second layer having a second dielectric permittivity different from the first dielectric permittivity. The first layer and the second layer define a Brewster angle substantially equal to the predetermined incidence angle based on the first dielectric permittivity and the second permittivity. Each photonic crystal structure in the plurality of photonic crystal structures defines a respective bandgap, and the respective bandgaps of the plurality of photonic crystal structures, taken together, cover a continuous spectral region of about 50 nm to about 100 mm.