LCOS Wavelength Selective Switch Optical Compensation Layer
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Solution Overview
Problem
Wavelength selective switches using liquid crystal on silicon (LCOS) experience significant loss due to the twisted effect of liquid crystal molecules at the peripheral parts, leading to reduced efficiency.
Innovation Solution
Incorporating an optical compensation layer, such as a λ/2 plate or a liquid crystal diffraction element, in the peripheral part of the LCOS to align the polarization state of incident light with the tilted liquid crystal molecules, thereby reducing diffraction loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a diffraction grating shape is presented to control diffraction direction in the LCOS, then light can be coupled to any emission port, but loss caused by twisted effect of liquid crystal molecules occurs in the peripheral part
Solution Approach 1:
The patent applies different optical properties to different regions of the LCOS device. Specifically, the liquid crystal molecules are oriented vertically in the central region to achieve diffraction control, while in the peripheral regions where total reflection occurs, the molecular orientation is modified to reduce the twisted effect. This local differentiation of molecular orientation resolves the contradiction by maintaining light coupling capability in the center while minimizing diffraction loss in the periphery.
Solution Approach 2:
The patent changes the orientation parameter of liquid crystal molecules based on position. By controlling the molecular orientation angle to be vertical in the central region and adjusted in peripheral regions, the device optimizes both diffraction control and loss reduction. This parameter change approach allows the system to achieve versatile light coupling while minimizing energy loss from twisted effects.
2Speed
If liquid crystal molecules are tilted in the peripheral part to achieve large diffraction angle, then more emission ports can be accessed, but loss caused by twisted effect increases
Solution Approach 1:
The patent implements local quality differentiation by maintaining vertical orientation of liquid crystal molecules in the peripheral regions where total reflection occurs, rather than tilting them to increase diffraction angle. This local optimization prevents the twisted effect that would result from tilting, thereby reducing diffraction loss while still allowing access to multiple emission ports through the central region's diffraction grating control.
Solution Approach 2:
The patent converts the potentially harmful twisted effect into a beneficial configuration by intentionally designing the peripheral region to have vertical molecular orientation that induces total reflection. This total reflection, while occurring at the periphery, actually benefits the system by redirecting light that would otherwise be lost to the correct emission ports, thereby converting what could be harmful loss into useful light routing.
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 optical compensation layer effectively minimizes the diffraction loss caused by the twisted effect of liquid crystal molecules, enhancing the overall efficiency of the wavelength selective switch.
Implementation Method 1
an optical compensation layer is disposed in a peripheral part of the liquid crystal on silicon
Implementation Method 2
a polarization controller that adjusts a polarization state of light incident from the input ports
Implementation Method 3
Each of the pixels can be driven by a voltage signal, and by presenting a phase pattern having a diffraction grating shape, a diffraction direction of incident light can be controlled
Implementation Method 4
a dispersive element that demultiplexes wavelength-multiplexed light incident from the input ports
Implementation Method 5
by presenting a phase pattern having a diffraction grating shape, a diffraction direction of incident light can be controlled
Data Source
AI summary
Provided is a wavelength selective switch where loss caused by a twisted effect of liquid crystal molecules of a LCOS peripheral part is reduced and the loss is small. The wavelength selective switch includes: one or more input ports; one or more output ports; a polarization controller that adjusts a polarization state of light incident from the input ports; a dispersive element that demultiplexes wavelength-multiplexed light incident from the input ports; and a deflection element that controls deflection of the demultiplexed light, in which the deflection element is a liquid crystal on silicon (LCOS) including an optical compensation layer that is provided on an incident surface to compensate for diffraction loss of a peripheral part.