HPDLC Medium Dynamic Angle Multiplexing Broadband Reflection
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Solution Overview
Problem
Conventional holographic polymer dispersed liquid crystal (HPDLC) mediums have difficulty reflecting a broad range of wavelengths due to narrow peak reflection wavelengths and increased light attenuation in stacked configurations, as well as complexity in fabricating multiple Bragg gratings in a single layer.
Innovation Solution
A new technique involving dynamic variation of the holography setup during HPDLC formation, such as rotating and translating motorized stages to vary the incident angles of laser beams, allowing for time and spatial multiplexing, which broadens the wavelength response of HPDLC mediums and enables the creation of broadband reflective properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple HPDLC mediums are bonded together in a stacked configuration to reflect a broad range of wavelengths, then the wavelength reflection range is improved, but light attenuation increases and manufacturing complexity increases
Solution Approach 1:
The patent segments the wavelength reflection function into multiple Bragg gratings within a single HPDLC layer, where each grating reflects a specific wavelength range. This is achieved by exposing the HPDLC mixture to multiple laser beams at different incident angles during fabrication, creating multiple alternating planes of polymer and liquid crystal droplets with different periodicities. The segmentation approach allows broad wavelength coverage without stacking multiple layers, thereby reducing light attenuation while maintaining manufacturing simplicity.
2Adaptability or versatility
If multiple HPDLC mediums are bonded together in a stacked configuration to reflect a broad range of wavelengths, then the wavelength reflection range is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple Bragg grating functions into a single HPDLC layer by simultaneously exposing the photopolymerizable mixture to multiple laser beams with different incident angles. This combining approach creates multiple alternating planes of polymer and liquid crystal droplets within one layer, each plane corresponding to a different wavelength reflection. The merging eliminates the need to bond multiple separate HPDLC layers, thereby reducing device complexity and manufacturing steps while achieving broad wavelength reflection.
3Adaptability or versatility
If simultaneous coherent multiple laser beam exposure is used to create multiple Bragg gratings in a single layer, then wavelength reflection range is improved, but fabrication complexity increases and additional lasers are required
Solution Approach 1:
The patent employs dynamic angular multiplexing where a single laser beam is sequentially redirected at different incident angles onto the HPDLC mixture during fabrication. A rotating mirror or goniometer dynamically changes the beam angle to create alternating planes of polymer and liquid crystal droplets with different periodicities. This dynamic approach replaces the need for multiple static laser beams, simplifying the fabrication setup while maintaining the capability to create multiple Bragg gratings in a single layer for broad wavelength reflection.
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 results in HPDLC mediums with improved optical response, capable of reflecting a broadband spectrum of wavelengths with enhanced reflection efficiencies and reduced complexity, achieving broadband reflective characteristics with multiple gratings in a single layer.
Implementation Method 1
exposure to a holographic interference pattern, typically formed by coherent lasers, polymerization is initiated
Implementation Method 2
polymerization is initiated, creating a diffusion gradient that in turn causes migration of liquid crystals
Implementation Method 3
resulting in the formation of a Bragg grating that can reflect a specific wavelength of light. The wavelength of light that will be reflected is determined in part by the incident angle of the laser beams
Data Source
AI summary
Described herein is a new holographic polymer dispersed liquid crystal (HPDLC) medium with broadband reflective properties, and a new technique for fabrication of broadband HPDLC mediums. The new technique involves dynamic variation of the holography setup during HPDLC formation, enabling the broadening of the HPDLC medium's wavelength response. Dynamic variation of the holography setup may include the rotation and/or translation of one or more motorized stages, allowing for time and spatial, or angular, multiplexing through variation of the incident angles of one or more laser beams on a pre-polymer mixture during manufacture. An HPDLC medium manufactured using these techniques exhibits improved optical response by reflecting a broadband spectrum of wavelengths. A new broadband holographic polymer dispersed liquid crystal thin film polymeric mirror stack with electrically-switchable beam steering capability is disclosed.