Spatial Light Modulator Fringe Field Reduction
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Solution Overview
Problem
Existing spatial light modulators (SLMs) face performance deterioration due to the fringe field effect (FFE), which causes unwanted phase shifts and reduces diffraction efficiency and phase profile accuracy, with existing techniques not adequately addressing this issue, especially as pixel electrode sizes shrink.
Innovation Solution
The SLM employs an inhomogeneous distribution of pretilt angles and anchoring energy within the liquid crystal layer over pixel electrodes without modifying their shape, using a nanostructured alignment layer and polymerized materials to counteract the FFE, ensuring phase-retardation accuracy across the pixel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an additional electrode is inserted between adjacent pixel electrodes to shield electric fields, then FFE is reduced, but non-uniformity in the resultant electric field causes phase curve error
Solution Approach 1:
The patent applies local quality by creating an inhomogeneous distribution of pretilt angles specifically at the boundaries of pixel electrodes. Instead of uniformly modifying the entire pixel structure, the invention selectively adjusts pretilt angles only in the regions where FFE occurs (at the boundaries), leaving the interior regions unchanged. This localized modification reduces FFE while maintaining uniform phase control across the pixel.
Solution Approach 2:
The invention changes physical parameters of the liquid crystal alignment by adjusting pretilt angles at pixel boundaries. By modifying the pretilt angle parameter locally at boundary regions rather than changing the overall pixel structure or adding electrodes, the patent reduces FFE while avoiding the introduction of additional electric field non-uniformities that would cause phase curve errors.
2Object-affected harmful factors
If corners of pixel electrodes are rounded to reduce electric fields at corners, then FFE is reduced to some extent, but the structural change is constrained by pixel size which is shrinking
Solution Approach 1:
Instead of globally modifying the pixel electrode shape (such as rounding corners), the patent applies local quality by modifying only the liquid crystal pretilt angle distribution at the boundary regions. This approach reduces FFE without altering the overall pixel electrode structure, thereby avoiding increased device complexity and remaining compatible with shrinking pixel sizes.
Solution Approach 2:
The invention replaces mechanical/structural modifications to the pixel electrode (such as rounding corners or changing geometry) with a field-based solution by adjusting liquid crystal pretilt angles. This substitution avoids physical structural changes that would complicate the electrode design and manufacturing, especially important as pixel dimensions decrease.
3Object-affected harmful factors
If non-rectangular pixel electrodes are used to compensate for FFE by changing electric field distribution, then FFE is reduced, but the extent of structural change is constrained by electrode size
Solution Approach 1:
The patent changes the pretilt angle parameter of the liquid crystal molecules at pixel boundaries rather than modifying the physical dimensions or shape of the pixel electrodes themselves. This parameter change approach allows FFE compensation without reducing the effective electrode size, maintaining both the electrode's functional area and its ability to generate sufficient electric field for liquid crystal modulation.
Solution Approach 2:
By applying local quality modifications to the liquid crystal alignment (pretilt angles) at boundary regions rather than globally changing electrode geometry, the invention reduces FFE while preserving the full area of the pixel electrode for light modulation, thus avoiding any reduction in the effective electrode size.
4Measurement precision
If the liquid crystal layer is configured with inhomogeneous distribution of pretilt angle to oppose FFE, then phase-retardation accuracy is maintained, but the alignment layer complexity increases
Solution Approach 1:
The patent implements local quality by creating an inhomogeneous pretilt angle distribution specifically at the boundary regions of pixel electrodes while maintaining uniform pretilt angles in the interior regions. This localized approach to the alignment layer modification achieves phase-retardation accuracy without requiring complex global restructuring of the entire alignment layer, thus limiting the increase in device complexity to only the necessary boundary regions.
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 approach effectively reduces FFE-induced phase fluctuations, maintaining phase-retardation accuracy and diffraction efficiency even under varying voltage conditions, enhancing the overall performance of the SLM without altering the pixel electrode design.
Implementation Method 1
The FFE is that the electric field generated at the boundary of a pixel electrode leaks to a neighboring pixel, affecting the LC alignment at the neighboring pixel
Implementation Method 2
the orientation results in a phase shift, commonly known as a phase retardation, to the light where the phase retardation is controllable by the voltage difference due to the Electric Controlled Birefringence Effect, (ECB Mode)
Implementation Method 3
An individual pixel is formed as a portion of the LC layer overlaying the pixel region of the individual pixel electrode. At least one of the pixels is realized as an optimized pixel, and most preferably each of the pixels is realized as the optimized pixel. The portion of the LC layer in the optimized pixel has an inhomogeneous distribution of FFE-opposing feature over the pixel region
Data Source
AI summary
A spatial light modulator (SLM) configured to reduce a fringe field effect (FFE) is provided. The SLM comprises pixels each having a liquid crystal (LC) on a pixel region. At least one pixel is an optimized pixel. The LC of the optimized pixel has an inhomogeneous distribution of pretilt angle or anchoring energy over the pixel region. The inhomogeneous distribution is selected to oppose the FFE. In one embodiment, the optimized pixel is partitioned into an outer region and an interior region. The outer region is an area between the optimized-pixel boundary and a pre-determined distance inwardly therefrom. The inhomogeneous distribution has one value of the pretilt angle or anchoring energy over the outer region and another value over the interior region. In another embodiment, a polymer stabilized network with an inhomogeneous polymerization degree over the pixel region is used to configure the LC layer to oppose the FFE.