Transmissive Liquid Crystal Diffraction Element for Unpolarized Light
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Solution Overview
Problem
Current liquid crystal diffraction elements cannot efficiently diffract different polarized light components in the same direction and have limited diffraction efficiency with unpolarized light, as they rely on twisted molecular structures that result in varying diffraction angles for polarized light, leading to inefficient light separation.
Innovation Solution
A transmissive liquid crystal diffraction element is designed with multiple optically-anisotropic layers having specific rotation and twist directions of their liquid crystal alignment patterns, allowing for the same direction diffraction of left and right circularly polarized light and enhanced diffraction efficiency with unpolarized light by adjusting the single periods and orientations of these layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single liquid crystal layer with twisted molecular structure is used, then the device structure is simple, but the diffraction efficiency for unpolarized light is at most 50% and different polarized light components cannot be diffracted in the same direction
Solution Approach 1:
The liquid crystal diffraction element is divided into multiple optically-anisotropic layers (first, second, third, and fourth layers) with different liquid crystal alignment patterns. Each layer has specific rotation directions and twisted directions that work together to diffract different polarized light components in the same direction, thereby achieving high diffraction efficiency for unpolarized light while maintaining a manageable structure
Solution Approach 2:
The invention uses composite optically-anisotropic layers with different liquid crystal alignment configurations. The first and second layers have opposite rotation directions and opposite twisted directions, while the third and fourth layers also have opposite rotation directions and opposite twisted directions. This composite structure enables the element to handle both polarized and unpolarized light efficiently
2Ease of operation
If twisted molecular structures are used to separate polarized light, then light separation occurs, but different polarized light components are diffracted in different directions rather than the same direction
Solution Approach 1:
The invention inverts the conventional approach by using layers with opposite rotation directions and opposite twisted directions. The first layer has a right-handed twisted structure while the second layer has a left-handed twisted structure, and similarly for the third and fourth layers. This inversion allows both circularly polarized light components to be diffracted in the same direction while still achieving light separation
Solution Approach 2:
Each optically-anisotropic layer is designed with specific local properties: the first and third layers have right-handed twisted structures, while the second and fourth layers have left-handed twisted structures. This local differentiation in twist directions enables the overall system to diffract different polarized light components in the same direction while maintaining effective light separation
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 the transmissive liquid crystal diffraction element to efficiently diffract both polarized and unpolarized light in a controlled manner, improving light separation and diffraction efficiency compared to existing technologies.
Implementation Method 1
a liquid crystal alignment pattern in which a direction of an optical axis derived from a liquid crystal compound changes while continuously rotating in at least one in-plane direction
Implementation Method 2
left circularly polarized light and right circularly polarized light incident into the polarization diffraction element are bent in opposite directions and separated
Data Source
AI summary
Provided is a transmissive liquid crystal diffraction element that can diffract different polarized light components in the same direction and has high diffraction efficiency with respect to unpolarized light. The transmissive liquid crystal diffraction element includes first to fourth optically-anisotropic layers each of which has a liquid crystal alignment pattern in which a direction of an optical axis changes while continuously rotating in at least one in-plane direction, in which the optical axis in each of the first to the fourth optically-anisotropic layers is twisted in a thickness direction, rotation directions of the optical axes in the liquid crystal alignment patterns and twisted directions of the optical axes in the thickness direction are opposite to each other in the first optically-anisotropic layer and the second optically-anisotropic layer, rotation directions of the optical axes in the liquid crystal alignment patterns and twisted directions of the optical axes in the thickness direction are opposite to each other in the third optically-anisotropic layer and the fourth optically-anisotropic layer, single periods of the liquid crystal alignment patterns are the same in the first optically-anisotropic layer and the second optically-anisotropic layer, single periods of the liquid crystal alignment patterns are the same in the third optically-anisotropic layer and the fourth optically-anisotropic layer, and the single periods of the liquid crystal alignment patterns are different in the first optically-anisotropic layer and the third optically-anisotropic layer.