Photonic Crystal NIR Filter Angle Insensitivity
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Solution Overview
Problem
Conventional decorative near-infrared (NIR) filters are either susceptible to environmental degradation, require complex fabrication processes, or suffer from angle-dependent transmission spectra, limiting their efficiency and cost-effectiveness for large-area applications.
Innovation Solution
A photonic crystal stack with less than 10 layers, comprising high and low refractive index materials, is designed to transmit NIR wavelengths while reflecting visible light, offering angle-insensitive performance and decorative color options, fabricated using a vacuum deposition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PC-based filters use more than ten layers to broaden the stopband, then visible light blocking performance is improved, but manufacturing cost and yield issues increase
Solution Approach 1:
The patent divides the photonic crystal structure into multiple periodic units, each contributing to the stopband. By optimizing the number and configuration of these units, the patent achieves broad visible light blocking without requiring excessive total layers, thus resolving the contradiction between blocking performance and structural complexity
Solution Approach 2:
The patent systematically varies parameters including layer thicknesses, refractive index contrasts, and periodic unit configurations to optimize the stopband bandwidth. By finding the optimal parameter combination, the patent achieves effective visible light blocking with reduced layer count compared to conventional filters
2Reliability
If subwavelength gratings are used to excite guided-mode resonance or surface plasmon polariton, then NIR transmission performance is improved, but fabrication complexity increases
Solution Approach 1:
The patent replaces complex subwavelength grating structures with a simpler one-dimensional photonic crystal stack consisting of alternating high and low index layers. This substitution maintains NIR transmission performance while enabling fabrication through standard thin-film deposition techniques, eliminating the need for complex lithography and etching processes
Solution Approach 2:
The patent changes the structural parameters from subwavelength periodic patterns to a layered configuration with controllable thicknesses and refractive indices. This parameter transformation simplifies the fabrication process while preserving the essential optical functionality of NIR transmission
3Ease of manufacture
If conventional PC-based filters use single-periodic stacks, then manufacturing is simplified, but stopband bandwidth is limited
Solution Approach 1:
The patent merges multiple periodic units with different layer thicknesses and refractive index configurations into a single integrated photonic crystal stack. This combination allows the structure to achieve broad stopband coverage across the visible spectrum while maintaining the manufacturing simplicity of periodic layered structures
Solution Approach 2:
The patent employs composite material strategies by combining multiple high index materials and low index materials in a periodic arrangement. This composite structure enables broad stopband formation through constructive interference across multiple wavelengths while preserving the ease of manufacturing through standard deposition processes
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 solution achieves high-efficiency NIR transmission with minimal angle dependence and decorative color generation, suitable for various applications, including imaging sensors and vehicle cockpits, with a streamlined manufacturing process.
Implementation Method 1
one-dimensional photonic crystal stacks
Implementation Method 2
transmitting a first portion of an electromagnetic spectrum having a first range of predetermined wavelengths in an infrared light range or near infrared light range and reflecting a second portion of the electromagnetic spectrum having a second range of predetermined wavelengths in a visible light range
Implementation Method 3
fabricated using a vacuum deposition process
Data Source
AI summary
A colored visibly opaque, highly efficient NIR-transmitting optical filter displaying angle insensitivity is based on one-dimensional photonic crystals. The filter comprises a photonic crystal stack comprising at least one high refractive index layer and two low refractive index layers respectively disposed along a first side and a second side of the high refractive index layer. The photonic crystal stack may have 10 or fewer layers. The filter transmits a first portion of an electromagnetic spectrum having a first range of predetermined wavelengths in an infrared light range or near infrared light range, while reflecting a second portion of the electromagnetic spectrum having a second range of predetermined wavelengths in a visible light range to generate a reflected output. In certain aspects, a refractive index contrast between the at least one high refractive index layer and at least one of the two low refractive index layers is ≥ about 40%.