Optical Filter Using SiC:H Medium Layers for Near IR Transmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical filters face limitations in accurately designing selective transmission for target wavelengths, particularly in the near IR spectrum, due to the refractive index properties of hydrogenated silicon (Si:H) layers, which affect transmission and blocking performance.
Innovation Solution
Incorporating medium refractive index layers with a refractive index of 3 or more, such as carbon-added hydrogenated silicon (SiC:H) layers, in conjunction with higher and lower refractive index layers, to enhance the design and performance of optical filters, allowing for high transmission and blocking in specific wavelength ranges while reducing thickness and blue shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hydrogenated silicon (Si:H) layers are used for higher refractive index layers, then the optical filter structure remains simple, but the transmission performance in near IR wavelength spectrum deteriorates due to high extinction coefficient
Solution Approach 1:
The patent segments the higher refractive index layer into two distinct materials: Si:H layers (refractive index 3.5-4.0) and SiC:H layers (refractive index 2.8-3.2). This segmentation allows each material to perform its optimal function - Si:H provides high refractive index for design flexibility while SiC:H provides low extinction coefficient for high transmission in near IR spectrum.
Solution Approach 2:
The patent employs composite material structure by combining Si:H and SiC:H layers within the higher refractive index group. This composite approach leverages the complementary properties of both materials - the high refractive index of Si:H and the low extinction coefficient of SiC:H - to achieve both design accuracy and high transmission performance simultaneously.
2Manufacturing precision
If the refractive index of Si:H layer is increased to improve design accuracy, then the extinction coefficient increases, but transmission performance deteriorates
Solution Approach 1:
The patent changes the material composition parameter by introducing SiC:H layers with different refractive index (2.8-3.2) compared to Si:H layers (3.5-4.0). This parameter change allows independent optimization of refractive index for design accuracy and extinction coefficient for transmission performance, breaking the direct coupling between these two parameters.
Solution Approach 2:
The patent applies local quality by assigning different material properties to different layers based on their specific functional requirements. Si:H layers are used where high refractive index is critical for wavelength selection, while SiC:H layers are used where low extinction coefficient is critical for high transmission, optimizing performance locally in each layer.
3Ease of manufacture
If conventional two-layer structure (higher and lower refractive index layers) is used, then manufacturing is simple, but accurate design for target wavelengths is limited
Solution Approach 1:
The patent introduces dynamic flexibility in the optical filter design by adding medium refractive index layers (SiC:H) that can be adjusted in thickness and positioning. This creates a more adaptable structure that can be tuned for precise wavelength selection while maintaining compatibility with existing manufacturing processes for depositing silicon-based thin films.
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 optical filter achieves 96% or more transmission in a specific wavelength range with minimal blue shift and high blocking performance, suitable for near IR wavelengths, by using a stack structure that includes pairs of higher and medium refractive index layers with optimized thicknesses, improving design accuracy and performance.
Implementation Method 1
an optical filter adapted to allow selective reflection, refraction, diffraction or absorption of light in a unwanted wavelength range while allowing transmission of light in the other wavelength range therethrough may be used
Implementation Method 2
an optical filter includes a filter stack disposed on a substrate and having a structure in which higher refractive index layers and lower refractive index layers are alternately stacked one above another
Implementation Method 3
an optical filter adapted to allow selective reflection, refraction, diffraction or absorption of light in a unwanted wavelength range
Data Source
AI summary
An optical filter includes a substrate and a first filter layer stacked on a first surface of the substrate. The first filter layer includes a plurality of lower refractive index layers having a refractive index of less than 3; a plurality of higher refractive index layers having a refractive index of greater than 3; and a plurality of medium refractive index layers having a refractive index of 3 or more and smaller than that of the higher refractive index layers, and one higher refractive index layer and one medium refractive index layer are interposed in at least one of regions between two lower refractive index layers.