LCOS Phase Modulator with Sub-wavelength Grating
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Solution Overview
Problem
Conventional liquid crystal on silicon (LCOS) devices are inherently polarization dependent, requiring additional components like quarter-wave plates and higher drive voltages to achieve polarization independence, which increases complexity and cost.
Innovation Solution
An optical phase modulator with a liquid crystal element and a pair of opposing electrodes, where at least some addressable pixels include a sub-wavelength grating structure with a periodic metallic profile, introducing a relative phase difference of 180° between orthogonal polarization components, reducing polarization dependence without additional optical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional LCOS devices are used, then polarization dependence is inherent, but additional components like quarter-wave plates and higher drive voltages are required to achieve polarization independence, increasing complexity and cost
Solution Approach 1:
The patent combines the quarter-wave plate functionality directly into the liquid crystal cell structure by introducing a birefringent layer between the electrodes. This integration merges the wave plate function with the liquid crystal modulation function, eliminating the need for separate optical components while achieving polarization independence
Solution Approach 2:
The liquid crystal cell is designed to perform multiple functions simultaneously: it modulates the phase of incident light while also compensating for polarization dependence through the integrated birefringent layer. This multi-functionality reduces the overall system complexity by eliminating dedicated polarization compensation components
2Adaptability or versatility
If conventional LCOS devices are used, then polarization dependence is inherent, but additional components like quarter-wave plates and higher drive voltages are required to achieve polarization independence, increasing cost
Solution Approach 1:
The patent combines the quarter-wave plate functionality directly into the liquid crystal cell structure by introducing a birefringent layer between the electrodes. This integration merges the wave plate function with the liquid crystal modulation function, eliminating the need for separate optical components while achieving polarization independence
Solution Approach 2:
The patent extracts the polarization compensation function from separate optical components and integrates it into the liquid crystal cell structure itself. By taking out the quarter-wave plate function and embedding it within the cell, the design reduces component count and associated costs
3Adaptability or versatility
If sub-wavelength grating structure is added to electrode, then relative phase difference of 180° is introduced between orthogonal polarization components, but device structure becomes more complex
Solution Approach 1:
The patent replaces mechanical or optical wave plate components with an electrostatically controlled liquid crystal-based phase modulation system. The sub-wavelength grating structure in the electrode enables precise control of phase differences through electrical fields, substituting mechanical polarization control with electro-optic control
Solution Approach 2:
The sub-wavelength grating structure is implemented only in specific regions of the electrode where it is most effective for introducing phase differences between polarization components. This localized approach allows polarization independence where needed while maintaining simpler structures elsewhere in the device
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 achieves polarization independence with reduced voltage requirements and minimal additional components, enabling efficient phase modulation for arbitrary input polarizations, suitable for applications like stereoscopic displays and holographic beam processors.
Implementation Method 1
LCOS devices can spatially manipulate optical signals by applying a spatially dependent phase profile to the signals. Each pixel is individually drivable by a voltage signal to provide a local phase change to an optical signal
Implementation Method 2
at least a subset of said addressable pixels include an anisotropic material profile in orthogonal lateral dimensions such that incident light transmitted through said liquid crystal element and onto said first electrode is reflected and experiences a relative phase difference between its constituent orthogonal polarization components
Implementation Method 3
incident light transmitted through said liquid crystal element and onto said first electrode is reflected and experiences a relative phase difference
Data Source
AI summary
Described herein is an optical phase modulator (20) including a liquid crystal element (22), disposed between a pair of opposing electrodes (24) and (26). The electrodes (24, 26) are electrically driven for supplying an electric potential V across the liquid crystal element (22) to drive the liquid crystals within element (22) in a predetermined configuration. Electrode (26) includes a grid of individually drivable pixel regions (28), at least some of which include a sub-wavelength grating structure that provides an anisotropic refractive index profile in orthogonal lateral dimensions, thereby creating an effective material form birefringence. Light incident through liquid crystal element (22) and onto electrode (26) is reflected and experiences a relative phase difference of 180° between its constituent orthogonal polarization components, thereby rotating each polarization component into the orthogonal orientation upon reflection.