Patterned Polarization Grating for Non-Polarized Light Conversion
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Solution Overview
Problem
Conventional polarization converters experience significant efficiency drops when converting non-polarized light, as they are highly dependent on the input light's polarization state, making them inefficient for non-polarized light sources.
Innovation Solution
A polarization converter system utilizing a patterned polarization grating with left and right hand domains, combined with retarders, lens arrays, and mirrors, which separates and converts non-polarized light into circular or linear polarized light with high efficiency, overcoming manufacturing challenges through a one-step multi-domain photoalignment process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional polarization converters are used, then the device structure is simple, but the conversion efficiency for non-polarized light decreases significantly
Solution Approach 1:
The polarization grating is divided into multiple domains with different handedness (left-handed and right-handed domains). Each domain converts non-polarized light to circularly polarized light with specific handedness, and the periodic arrangement ensures that both types of domains work together to achieve high conversion efficiency for non-polarized light while maintaining a relatively simple overall device structure.
2Manufacturing precision
If laser beam interference is used to create spatially varying alignment, then the polarization grating can be fabricated, but the manufacturing process becomes highly sensitive to vibrations and airflow
Solution Approach 1:
The patent replaces the mechanical/optical interference-based alignment method with a photoalignment process that uses photopolymerization to create the spatially varying liquid crystal alignment pattern. This substitution eliminates the sensitivity to vibrations and airflow that plagues laser beam interference methods, while still achieving the required precision in creating the polarization grating structure.
3Device complexity
If conventional polarizers are used, then the device is simple, but the conversion efficiency drops significantly for non-polarized light
Solution Approach 1:
The patent changes the fundamental parameter of how polarization conversion is achieved by using a polarization grating with periodic spatial variation in optical axis orientation, rather than conventional polarizers that rely on absorption or simple reflection. This parameter change enables the device to maintain high conversion efficiency for non-polarized light while keeping the overall device structure relatively simple.
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 system achieves conversion efficiencies close to 100% for non-polarized light to polarized light, outperforming conventional polarizers, and is suitable for applications like Liquid Crystal on Silicon (LCOS) projectors, with efficiencies exceeding 90% even with non-collimated input light.
Implementation Method 1
a PG is a sinusoidal phase grating made of a retardation film with spatially varying optical axis. Different from other optical gratings, a PG diffracts light into +1 and −1 diffraction order
Implementation Method 2
The polarization grating domains are configured to diffract incident non-polarized light into beams having left and right circular polarization states
Data Source
AI summary
A polarization converter and polarization conversion systems are provided. The polarization converter and polarization conversion systems include a patterned polarization grating with left hand and right hand polarization grating domains. The polarization grating domains are configured to diffract incident non-polarized light into beams having left and right circular polarization states.