Gradient-Pitch Liquid Crystal Optical Element for Refractive Index Detection
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Solution Overview
Problem
Existing optical elements using guided-mode resonance phenomena require complex manufacturing methods and necessitate high-precision spectroscopes for detecting shifts in peak wavelengths to measure refractive indices, making them cumbersome for practical applications.
Innovation Solution
An optical element with a liquid crystal layer having a liquid crystal alignment pattern where the optical axis rotates continuously, featuring a gradually changing single period, allowing for refractive index detection without sweeping incidence light wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a liquid crystal diffraction element with guided-mode resonance phenomenon is used for refractive index sensing, then measurement sensitivity is improved, but device complexity increases due to requiring high-precision spectroscope and wavelength sweeping capability
Solution Approach 1:
The patent changes the structural parameters of the liquid crystal layer by introducing a gradient in the liquid crystal alignment pattern, where the orientation of the optical axis rotates continuously and the pitch varies spatially. This structural parameter change creates a spectrum of resonance wavelengths across different regions of the layer, enabling direct visual detection of refractive index changes without requiring complex wavelength sweeping equipment.
Solution Approach 2:
The patent transitions from a uniform liquid crystal layer to one with spatially varying properties in the in-plane direction. The liquid crystal alignment pattern creates a gradient structure where the orientation and pitch vary across the surface, adding a spatial dimension to the resonance response. This dimensional change allows the system to encode multiple resonance wavelengths across the surface area, enabling direct observation of refractive index changes through spatial distribution rather than temporal wavelength scanning.
2Ease of manufacture
If a uniform liquid crystal layer with fixed pitch is used, then manufacturing is simplified, but the ability to detect refractive index changes without wavelength sweeping is lost
Solution Approach 1:
The patent introduces a gradient in the pitch parameter across the liquid crystal layer while maintaining the basic liquid crystal alignment process. The pitch varies spatially in the in-plane direction, creating different resonance conditions across different regions. This parameter variation enables direct visual detection of refractive index changes through the spatial distribution of reflected wavelengths, simplifying the detection operation while remaining compatible with standard liquid crystal fabrication techniques.
3Manufacturing precision
If the liquid crystal alignment pattern has a constant period, then manufacturing precision requirements are reduced, but measurement capability for refractive index changes is diminished
Solution Approach 1:
The patent implements a gradient in the period parameter of the liquid crystal alignment pattern, where the pitch varies continuously or in steps across the in-plane direction. This creates a distribution of resonance wavelengths across different regions of the layer. The gradient structure maintains relatively relaxed manufacturing tolerances compared to subwavelength gratings while providing enhanced measurement capability through the spatial variation of resonance conditions.
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
Enables easy detection of refractive index changes using a simpler setup, eliminating the need for precise wavelength sweeping devices and enhancing measurement accuracy.
Implementation Method 1
an optical element using an optical phenomenon by a fine structure of a thing, an optical element (optical device) using a guided-mode resonance phenomenon is known
Implementation Method 2
the peak wavelength of reflected light is shifted depending on the refractive index of the member disposed on the liquid crystal layer
Data Source
AI summary
Provided are an optical element capable of more easily detecting a change in refractive index of an object to be measured without sweeping a wavelength of incidence light, and an optical sensor using the optical element. An optical element includes a liquid crystal layer that is formed of a composition including a liquid crystal compound, in which the liquid crystal layer has a liquid crystal alignment pattern in which an orientation of an optical axis derived from the liquid crystal compound changes while continuously rotating toward at least one direction of in-plane directions, in a case where a length over which the orientation of the optical axis derived from the liquid crystal compound rotates by 180° in a plane is set as a single period, a length of the single period in the liquid crystal alignment pattern gradually changes in the one direction, and the liquid crystal layer has a resonance structure.