Liquid Crystal Phase Modulator with Asymmetric Out-of-Plane Angles
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Solution Overview
Problem
Existing phase modulators for polarized light face challenges in achieving the optical function of a λ/2 plate with liquid crystal materials, requiring high birefringence and low dielectric anisotropy, which is difficult to achieve simultaneously, leading to reduced diffraction efficiency and unwanted light perturbations.
Innovation Solution
A phase modulator with substrates and a liquid crystal layer where the liquid crystal molecules are oriented at out-of-plane angles between 0 and 45 degrees on each substrate, allowing for adjustable in-plane component rotation and using materials with typical birefringence and dielectric anisotropy values, enabling efficient phase modulation and deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hybrid alignment with out-of-plane orientation is used to achieve phase modulation, then the optical function of λ/2 plate can be achieved, but the required high birefringence and low dielectric anisotropy are difficult to achieve simultaneously
Solution Approach 1:
The patent changes the orientation parameters of liquid crystal molecules by introducing out-of-plane angles (α and γ) in addition to the in-plane angle (φ). This allows the system to achieve the λ/2 plate optical function with conventional liquid crystal materials that have typical birefringence and dielectric anisotropy values, rather than requiring extreme material properties. The effective birefringence becomes a function of these orientation parameters, enabling precise optical control.
2Ease of manufacture
If conventional liquid crystal materials with typical birefringence and dielectric anisotropy are used, then material availability is improved, but diffraction efficiency is reduced and unwanted light perturbations occur
Solution Approach 1:
The patent transitions from conventional two-dimensional in-plane orientation control to three-dimensional orientation control by incorporating out-of-plane angles. This additional dimensional control allows the system to maintain high diffraction efficiency and minimize light perturbations when using conventional liquid crystal materials, as the out-of-plane components provide an extra degree of freedom for optimizing the optical path and phase modulation.
3Stability of the object's composition
If out-of-plane angles are introduced for phase modulation, then optical path variations are reduced, but the complexity of orientation control increases
Solution Approach 1:
The patent introduces asymmetric out-of-plane angles (α at the first substrate, γ at the second substrate) that can be independently optimized. This asymmetric configuration allows for fine-tuning of the optical path through the liquid crystal layer, compensating for variations and achieving stable phase modulation. The asymmetry provides additional control parameters that can be adjusted to minimize optical path variations without requiring symmetric complexity.
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
This configuration maintains high diffraction efficiency while allowing for rapid switching and reduced optical path variations, using conventional liquid crystal materials, thus overcoming the limitations of hybrid alignment and minimizing the impact of dielectric anisotropy on the optical function.
Implementation Method 1
The effective birefringence for light which passes through an LC layer, the LC molecules being tilted at an angle β with respect to the direction in which the light passes through, is... where n1 and n2 are the ordinary and extraordinary refractive indices of the liquid crystal with the birefringence Δn=n2−n1
Implementation Method 2
The effective optical path difference (opd), which in the case of uniform LC orientation is usually described as opd=d Δn with the layer thickness d and the birefringence Δn
Implementation Method 3
The sign-dependent rotation in the electric field is in this case based on flexoelectric polarization. This polarization is based on a mechanical deformation of the LC, or the LC molecules, by the hybrid alignment
Implementation Method 4
an electrode arrangement, based on an LC alignment (LC=liquid crystal) with a large pretilt angle
Data Source
AI summary
A phase modulator for polarized light, comprising a first substrate with a first surface and a second substrate with a second surface, a liquid crystal layer between the two substrates and an electrode arrangement. The phase modulator is usable as a variable deflection grating, and liquid crystal materials which are currently conventional are usable for its production. A phase modulator has an out-of-plane angle of the liquid crystal molecules next to the two surfaces whose magnitude is greater than 0 but less than or equal to 45 degrees, and an electrode arrangement controllable such that an in-plane component of the liquid crystal molecule orientation is adjustable in an angle range of up to 180 degrees, and the rotation sense of the liquid crystal molecules next to the first surface is opposite to the rotation sense of the liquid crystal molecules next to the second surface.