Subwavelength Wavelength Filter Structure for Sharper Color Selectivity
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Solution Overview
Problem
Existing wavelength selective filters using guided-mode resonance phenomenon struggle to enhance wavelength selectivity and prevent emission of unwanted light wavelengths.
Innovation Solution
A wavelength selective filter configuration with a concavo-convex structure layer, a high refractive index layer with two grating regions, and a low refractive index layer, which enhances the guided-mode resonance phenomenon to increase reflected light intensity and selectively cancel unwanted wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single subwavelength grating structure is used, then the manufacturing process is simple, but the wavelength selectivity is insufficient and unwanted wavelengths cannot be effectively suppressed
Solution Approach 1:
The single grating structure is divided into two separate subwavelength grating regions with different periods. The first grating region has a first period and the second grating region has a second period different from the first period. This segmentation allows each grating region to target specific wavelength ranges, thereby improving wavelength selectivity while maintaining manufacturing simplicity through a unified fabrication process.
Solution Approach 2:
Different regions of the filter are assigned different grating periods to optimize performance for specific wavelength ranges. The first grating region is designed with a first period optimized for one wavelength range, while the second grating region is designed with a second period optimized for another wavelength range. This local differentiation enables precise control over which wavelengths are reflected and which are transmitted.
2Illumination intensity
If the refractive index difference between substrate and protrusions is increased, then the intensity of reflected light increases, but the manufacturing cost increases due to requiring SOQ substrate
Solution Approach 1:
Instead of changing the material composition to achieve high refractive index difference, the invention changes the geometric parameters of the grating structures. By optimizing the periods, depths, and width ratios of the two grating regions, the design achieves strong reflected light intensity using conventional materials like resin, thereby avoiding the need for expensive SOQ substrates while maintaining high performance.
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 proposed configuration significantly improves wavelength selectivity, increasing the intensity of reflected light and reducing the emission of unwanted wavelengths, thereby enhancing the sharpness and brightness of colors in displays.
Implementation Method 1
a wavelength selective filter using a guided-mode resonance phenomenon have been proposed as filters for selecting light by using an optical phenomenon caused by a fine structure of an object
Implementation Method 2
light in a specific wavelength range propagates with multiple reflections due to a difference in refractive index between a region where the subwavelength grating is located and a peripheral region thereof, causing resonance at which reflected light is strongly emitted
Implementation Method 3
a subwavelength grating, which is a diffraction grating with a period smaller than the wavelength of light
Data Source
AI summary
An optical device including a concavo-convex structure layer composed of a plurality of protrusions arranged having a subwavelength period; a high refractive index layer located on the concavo-convex structure and having a surface shape following the concavo-convex structure; and a low refractive index layer located on the high refractive index layer and having a surface shape following a concavo-convex structure on a surface of the high refractive index layer. The high refractive index layer includes a first grating high refractive index region located on a bottom of the concavo-convex structure to form a subwavelength grating, and a second grating high refractive index region located on a top of the concavo-convex structure to form a subwavelength grating. The high refractive index layer has a refractive index higher than both the refractive indices of the concavo-convex structure layer and the low refractive index layer.