Laminated Cholesteric Liquid Crystal Diffraction Element
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Solution Overview
Problem
Current liquid crystal diffraction elements either lack wavelength selectivity or are not capable of diffraction while allowing transmission of incident light across the entire wavelength range, failing to provide a solution for applications requiring selective wavelength diffraction and transmission.
Innovation Solution
A liquid crystal diffraction element comprising a first and second cholesteric liquid crystal layer with aligned optical axes, where the selective reflection wavelengths are the same, and the single periods of their alignment patterns differ, allowing for wavelength-selective diffraction and transmission by adjusting the pitch and alignment patterns of the cholesteric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a liquid crystal diffraction element is designed to diffract incident light across the entire wavelength range, then transmission of incident light is improved, but wavelength selectivity deteriorates
Solution Approach 1:
The liquid crystal diffraction element is divided into multiple liquid crystal layers, each layer having different grating periods. This segmentation allows each layer to handle different wavelength ranges, with shorter wavelength layers positioned closer to the light source. This resolves the contradiction by enabling wavelength-selective diffraction while maintaining overall transmission through the stacked structure.
Solution Approach 2:
Different regions of the liquid crystal element (specifically different layers) are assigned different grating periods tailored to specific wavelength ranges. The first liquid crystal layer has a grating period optimized for shorter wavelengths, while the second layer has a grating period for longer wavelengths. This local differentiation of properties enables simultaneous wavelength selectivity and broad transmission.
2Manufacturing precision
If a liquid crystal diffraction element is designed with strong wavelength selectivity, then wavelength-selective diffraction is improved, but transmission of incident light deteriorates
Solution Approach 1:
The element is segmented into multiple layers with progressively different grating periods. This allows the stronger diffraction effect (wavelength selectivity) to be concentrated at specific wavelength ranges while other wavelengths pass through with minimal interference, thus maintaining overall transmission.
Solution Approach 2:
The solution moves from a single-layer design to a multi-layer stacked structure, adding the dimension of layer depth. This dimensional expansion allows wavelength selectivity to be achieved in the spectral domain while maintaining transmission through the spatial stacking arrangement.
3Manufacturing precision
If multiple liquid crystal layers with different grating periods are stacked, then wavelength selectivity is improved, but device complexity increases
Solution Approach 1:
The complex wavelength-selective function is segmented across multiple layers, with each layer handling a specific wavelength range. This segmentation simplifies the design of individual layers while achieving complex overall functionality, as each layer can be optimized independently for its target wavelength range.
Solution Approach 2:
The stacked liquid crystal layer structure serves multiple functions simultaneously: it provides wavelength-selective diffraction, maintains broad spectral transmission, and enables compact integration of multiple diffraction gratings with different periods in a single element.
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 enables a transmission-type diffraction element with wavelength selectivity, effectively diffracting specific wavelengths while allowing other wavelengths to pass through, enhancing optical device performance by providing controlled light refraction and transmission.
Implementation Method 1
a liquid crystal diffraction element comprising: a first cholesteric liquid crystal layer obtained by cholesteric alignment of a liquid crystal compound; and a second cholesteric liquid crystal layer that is laminated on the first cholesteric liquid crystal layer
Implementation Method 2
a first cholesteric liquid crystal layer obtained by cholesteric alignment of a liquid crystal compound
Implementation Method 3
the first cholesteric liquid crystal layer and the second cholesteric liquid crystal layer have a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction
Implementation Method 4
a selective reflection wavelength of the first cholesteric liquid crystal layer and a selective reflection wavelength of the second cholesteric liquid crystal layer are the same
Implementation Method 5
the single period of the liquid crystal alignment pattern of the first cholesteric liquid crystal layer and the single period of the liquid crystal alignment pattern of the second cholesteric liquid crystal layer are different from each other
Data Source
AI summary
Provided are a liquid crystal diffraction element that diffracts incident light while allowing transmission of the incident light and has wavelength selectivity, and a laminated diffraction element. The liquid crystal diffraction element includes: a first cholesteric liquid crystal layer obtained by cholesteric alignment of a liquid crystal compound; and a second cholesteric liquid crystal layer that is laminated on the first cholesteric liquid crystal layer, in which the first cholesteric liquid crystal layer and the second cholesteric liquid crystal layer have a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction, a selective reflection wavelength of the first cholesteric liquid crystal layer and a selective reflection wavelength of the second cholesteric liquid crystal layer are the same, and in a case where a length over which the direction of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotates by 180° in a plane is set as a single period, a single period of the liquid crystal alignment pattern of the first cholesteric liquid crystal layer and a single period of the liquid crystal alignment pattern of the second cholesteric liquid crystal layer are different from each other.