Switchable Broadband Waveplate Using Ferroelectric Liquid Crystal Layers
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Solution Overview
Problem
Current liquid crystal (LC) waveplates, particularly those based on nematic LCs, fail to achieve broadband performance, large acceptance angle, low residual retardance, fast response, and switchability between different states due to limitations in response time and residual retardance.
Innovation Solution
The optical waveplate comprises a plurality of liquid crystal layers, with at least one layer being in-plane switchable by an external field, allowing for switching between different phase retardance states, utilizing ferroelectric liquid crystal (FLC) cells to achieve broadband performance and low residual retardance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If nematic LC waveplates are used to achieve non-mechanical tuning of retardance, then the waveplate can be switched between different states, but the response time is slow (on the order of milliseconds) and residual retardance is large
Solution Approach 1:
The patent changes the material parameter from nematic LC to ferroelectric LC, which fundamentally alters the switching mechanism. Ferroelectric LC molecules can be reoriented along an external electric field with microsecond response times and achieve complete alignment, eliminating the millisecond response and large residual retardance characteristic of nematic LC waveplates
Solution Approach 2:
The patent utilizes the ferroelectric phase transition properties of FLC materials. The FLC molecules exhibit a specific phase transition behavior that enables fast, complete reorientation along the electric field direction, achieving both fast response and low residual retardance simultaneously
2Ease of operation
If nematic LC molecules are used, then non-mechanical tuning is achieved, but the molecules cannot be fully reoriented along the external electric field resulting in large residual retardance
Solution Approach 1:
The patent changes the material parameter from nematic LC to ferroelectric LC, which fundamentally alters the switching mechanism. Ferroelectric LC molecules can be reoriented along an external electric field with microsecond response times and achieve complete alignment, eliminating the millisecond response and large residual retardance characteristic of nematic LC waveplates
3Device complexity
If a single LC layer is used, then the device structure is simple, but broadband performance and large acceptance angle cannot be achieved
Solution Approach 1:
The patent divides the waveplate into multiple LC layers (first and second LC layers with different retardances). This segmentation allows each layer to contribute differently to the overall optical performance, enabling broadband operation and large acceptance angle while maintaining reasonable structural complexity
Solution Approach 2:
The patent creates a composite structure by stacking multiple LC layers with different optical properties. The combination of layers with different retardances and orientations produces synergistic effects that achieve broadband performance and large acceptance angle that cannot be obtained with a single LC layer
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 optical waveplate to maintain polarization over a wide range of wavelengths and angles, with fast switching and low residual retardance, suitable for applications like near-eye displays and varifocal systems.
Implementation Method 1
At least one of the plurality of LC layers includes LC molecules that are in-plane switchable by an external field to switch the optical waveplate between states of different phase retardances
Implementation Method 2
A waveplate controls the polarization by retarding (or delaying) a component of polarization (or a polarization component) with respect to an orthogonal component
Data Source
AI summary
A waveplate is provided. The waveplate includes a first liquid crystal (“LC”) layer including LC molecules that are in-plane switchable by an external field to switch the waveplate between states of different phase retardances. The waveplate includes a second LC layer and a third LC layer sandwiching the first LC layer. Azimuthal angles of effective refractive index ellipsoids of the second LC layer and the third LC layer are different.