Optical Filter With Segmented Metal Structures
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Solution Overview
Problem
Hole-type metallic thin film filters have low transmittance due to high light absorption, limiting their application in visible light regions and offering limited size selection flexibility due to dominant pitch-dependent optical characteristics.
Innovation Solution
A dielectric substrate with two-dimensionally arranged metal structures, covered by a dielectric layer, where the metal structures are designed to induce localized surface plasmons for enhanced transmittance and reflectance, allowing for a high-transmittance optical filter with reduced light absorption and increased size selection freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hole-type metallic thin film filter is used to achieve wavelength selection via surface plasmons, then the transmission spectrum can be controlled, but the transmittance becomes low (5-6%) due to high light absorption by metal
Solution Approach 1:
The continuous metallic thin film is segmented into discrete metal structures (such as metal particles or patterns) arranged on the dielectric substrate. This segmentation reduces the total metal content and associated light absorption while preserving the surface plasmon resonance effect for wavelength selection. The discrete structures act as individual plasmon generators that can be optimized for minimal absorption.
Solution Approach 2:
The metal structures are designed with specific local geometries (size, shape, arrangement) to optimize the localized surface plasmon resonance at desired wavelengths. By controlling the local characteristics of each metal structure, the filter achieves precise wavelength selection with reduced overall metal content, thereby minimizing light absorption while maintaining spectral control capability.
2Loss of energy
If the pitch of peripheral structures is increased to reduce metal density, then light absorption decreases, but the optical characteristics become less effective due to reduced surface plasmon coupling
Solution Approach 1:
The invention optimizes multiple parameters simultaneously including metal structure size, shape, material composition, and spatial arrangement to achieve the desired balance. By changing these parameters, the system can maintain effective surface plasmon coupling even with reduced metal density, avoiding the need for high pitch values that would weaken optical characteristics.
3Measurement precision
If a large surface area metal film is used to enhance surface plasmon effects, then transmission spectrum control improves, but the device size increases and manufacturing complexity increases
Solution Approach 1:
The large continuous metal film is divided into multiple discrete metal structures distributed across the substrate. Each structure is small and simple to manufacture, but collectively they provide the necessary surface plasmon effects. This segmentation allows for reduced individual structure size and simplified manufacturing while maintaining overall spectral control capability.
Solution Approach 2:
The discrete metal structures serve multiple functions simultaneously: they act as wavelength-selective elements, reduce light absorption, and can be arranged to provide spatial filtering capabilities. This multi-functionality reduces the need for separate components and simplifies the overall device design.
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 provides a high-transmittance optical filter with reduced light absorption in the visible light region and increased flexibility in size selection, enabling improved performance and application in devices such as image capturing and light-detecting systems.
Implementation Method 1
a transmittance of the first wavelength being made minimal or a reflectance of the first wavelength being made maximal by localized surface plasmons induced on a surface of the first metal structures by resonance between light incident on the dielectric substrate or the dielectric layer and the first metal structures
Data Source
AI summary
An optical filter that transmits light of the visible light region includes a dielectric substrate; a dielectric layer that is formed on a surface of the dielectric substrate; and a first metal structure group in which a plurality of first metal structures are arranged two-dimensionally in an isolated state in the in-plane direction of the dielectric substrate, that is provided between the dielectric substrate and the dielectric layer, comprising: the first metal structures having first and second lengths in first and second directions orthogonal to each other, which lengths are equal to or less than a first wavelength in the visible light region; and a transmittance of the first wavelength being reduced or a reflectance being increased by surface plasmons induced on a surface of the first metal structures by resonance between light incident on the dielectric substrate or the dielectric layer and the first metal structures.