Transmission Diffraction Element 4-Layer Composite Structure
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Solution Overview
Problem
Current transmission diffraction elements face challenges in achieving high diffraction efficiency and low polarization dependence across the entire wavelength region, with existing solutions requiring complex manufacturing processes and specific material combinations that are difficult to produce and maintain.
Innovation Solution
A transmission diffraction element with a 4-layer structure of alternately stacked high and low refractive index materials, specifically using Si3N4, TiO2, Nb2O5, Ta2O5 for high refractive index and SiO2, SiON for low refractive index materials, to enhance diffraction efficiency and reduce polarization dependence, while simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the grating period is reduced to increase wavelength resolution, then wavelength resolution is improved, but diffraction efficiency deteriorates when light passes through multiple times
Solution Approach 1:
The patent applies composite materials by stacking multiple layers with different refractive indices (high refractive index layers and low refractive index layers) to form the diffraction element. This composite structure enhances diffraction efficiency while maintaining the reduced grating period needed for high wavelength resolution, thereby resolving the contradiction between wavelength resolution and diffraction efficiency.
2Loss of energy
If a 3-layer structure with specific refractive index relationships is used to achieve high diffraction efficiency, then diffraction efficiency is improved, but manufacturing complexity increases due to requiring three different materials and large deposition apparatus
Solution Approach 1:
The patent segments the diffraction element into alternating high refractive index layers and low refractive index layers. This segmentation allows the use of only two types of materials instead of three, simplifying the manufacturing process and reducing the number of deposition sources required while maintaining high diffraction efficiency.
Solution Approach 2:
The patent changes the structural parameters by adopting a 4-layer configuration with alternating refractive indices rather than a 3-layer structure. This parameter change enables the use of fewer material types and simplifies the deposition process while achieving the desired diffraction efficiency through optimized layer thicknesses and refractive index contrasts.
3Loss of energy
If oblique incidence is used to generate only +1st-order diffracted light, then light utilization efficiency is improved, but polarization dependence increases
Solution Approach 1:
The patent uses composite materials with alternating high and low refractive indices in a multi-layer structure. This composite configuration is designed to minimize polarization dependence while maintaining high light utilization efficiency through oblique incidence, by optimizing the refractive index contrast and layer thicknesses to achieve uniform diffraction performance across different polarizations.
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 diffraction efficiency (98% or higher) and low polarization dependence across a wide wavelength range, with a simplified manufacturing process using fewer deposition sources and reducing manufacturing complexity.
Implementation Method 1
a transmission diffraction element that transmits and diffracts incident light
Implementation Method 2
each of the plurality of convex parts includes a first layer, a second layer, a third layer, and a fourth layer that are stacked on the transparent substrate, the first layer and the third layer are made of a first material having a high refractive index, and the second layer and the fourth layer are made of a second material having a low refractive index
Data Source
AI summary
A transmitting diffraction element may include a transparent substrate, and a plurality of convex parts periodically formed on one surface of the transparent substrate, and be configured to diffract incident light to the transparent substrate. Each of the convex parts may include first, second, third, and fourth layers that are stacked on the transparent substrate. The first and third layers may be made of a material having a high refractive index, and the second and fourth layers may be made of a material having a low refractive index that is lower than the high refractive index.