Asymmetric Metal Grating Beam Splitter for Low TE Reflection
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Solution Overview
Problem
Existing polarized light beam splitters using metal gratings face challenges in achieving high extinction ratios and broadband performance due to high TE light reflection, which affects device efficiency and integration in applications like display devices.
Innovation Solution
A reflection-asymmetric metal grating polarization beam splitter design that incorporates light-absorbing materials and strategically designed gratings to absorb TE light and control TM light transmission, achieving low TE reflectance and high TM transmission across a broad spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If metal gratings are used to achieve broadband polarization beam splitting, then the spectrum range is widened, but the TE light reflection becomes too high causing device inefficiency
Solution Approach 1:
The patent applies local quality by creating asymmetric grating structures where different regions have different properties. Specifically, the grating has different geometrical parameters (width, height, period) in different zones, allowing the structure to exhibit low TE reflection in certain regions while maintaining high TM transmission, thus resolving the contradiction between broadband performance and energy loss.
Solution Approach 2:
The core of the invention is the asymmetric grating structure where the unit cell consists of a metal rod with specific width and height ratios, and the grating period is asymmetrically designed. This asymmetry breaks the symmetry of light-matter interaction, enabling differential control over TE and TM polarizations, achieving low TE reflection while maintaining broadband operation.
2Device complexity
If traditional crystal or medium gratings are used, then the structure is simple, but the extinction ratio is difficult to improve beyond hundreds to thousands
Solution Approach 1:
The patent employs composite materials by combining metal (such as aluminum, gold, or silver) with dielectric materials to form a hybrid grating structure. This composite approach leverages the plasmonic properties of metals to enhance light-matter interaction, achieving extinction ratios of 10,000 or higher while maintaining a relatively simple periodic grating geometry that is easier to manufacture than complex multilayer dielectric structures.
3Reliability
If metal gratings with high TE reflection are used, then the polarization beam splitting effect is strong, but ambient light reflection increases affecting display device performance
Solution Approach 1:
The asymmetric grating design creates local quality variations where specific regions of the unit cell are optimized to minimize TE reflection while maintaining polarization beam splitting. By carefully designing the width, height, and position of grating elements, the structure achieves directional control of reflected light, reducing ambient light reflection in viewing directions while preserving the polarization splitting function.
Solution Approach 2:
The patent utilizes parameter changes by systematically varying the geometrical parameters of the grating (width w, height h, period P, and aspect ratios) to optimize the balance between polarization beam splitting efficiency and ambient light reflection. Through parameter optimization, the extinction ratio is maximized while TE reflection is suppressed to acceptable levels for display applications.
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 design achieves high transmission polarization suppression ratios and stable performance with low TE reflection and high TM transmission, suitable for mass production and integration in optical devices.
Implementation Method 1
The metal gratings support surface plasma waves, and TM polarized light of any wavelength can excite the surface plasma waveguide mode to be propagated in medium slits of the metal gratings
Implementation Method 2
light-absorbing materials and a second grating located on the first metals... TE polarized light incident from the grating surface is absorbed by utilizing the light absorption performance of second light-absorbing materials
Implementation Method 3
Under the interference effect, TM and TE light are diffracted backward or forward to a specific direction related to the light wavelength
Data Source
AI summary
The reflection-asymmetric metal grating polarization beam splitter comprises a substrate, and a first grating composed of first mediums and first metals, and first light-absorbing materials are provided on the upper surfaces or side surfaces of the first metals. A plurality of second materials are provided at equal intervals longitudinally along the upper surfaces of the first metals to form a second grating. The first light-absorbing materials are closely provided on the upper surfaces of the first metals between two adjacent second materials, and second light-absorbing materials are closely provided on the upper surfaces and/or side surfaces of the second materials. The second materials have a greater thickness than the first light-absorbing materials. Second mediums are filled in spaces between adjacent second materials above the first light-absorbing materials.