Asymmetric Waveguide Mode Converter for TE-TM Polarization Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing laser modules in near-eye wearable devices face inefficiencies in converting the polarization mode of visible light due to the inclusion of both TE and TM modes, necessitating improved conversion efficiency to enhance image projection quality.
Innovation Solution
The implementation of an optical element with a core layer containing mode converters having asymmetric waveguides that convert polarization modes between TE and TM modes, utilizing lithium niobate thin films to optimize refractive indices and field components for high-efficiency conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional optical modulator uses a lithium niobate film waveguide, then the device can modulate visible light, but the modulation efficiency varies depending on polarization mode (TE or TM) and conversion efficiency between polarization modes is insufficient
Solution Approach 1:
The patent applies asymmetry by designing the third waveguide with an asymmetric cross-sectional shape (different width in the vertical direction compared to the horizontal direction). This asymmetric structure creates different effective refractive indices for TE and TM modes, enabling efficient polarization mode conversion. The asymmetric waveguide transforms the electric field components, converting light from one polarization mode to another with high efficiency, thereby resolving the polarization-dependent efficiency issue.
Solution Approach 2:
The patent changes the structural parameters of the waveguide, specifically the dimensions and shape of the third waveguide, to optimize polarization mode conversion. By adjusting the waveguide width, height, and aspect ratio, the effective refractive indices for different polarization modes are tuned to achieve maximum conversion efficiency. This parameter optimization enables the device to efficiently handle both TE and TM modes without requiring complex external polarization control mechanisms.
2Productivity
If the polarization mode of visible light from the laser light source differs from the desired polarization mode, then conversion is necessary, but the conversion efficiency is insufficient with conventional methods
Solution Approach 1:
The asymmetric third waveguide structure is the key to achieving high polarization mode conversion efficiency. The asymmetric geometry creates a mode profile where the electric field has equal horizontal and vertical components, enabling efficient coupling between TE and TM modes. This asymmetric design allows the converter to transform polarization modes with minimal energy loss, directly addressing the conversion efficiency problem.
Solution Approach 2:
The third waveguide acts as an intermediary structure between the first waveguide (input) and the second waveguide (output). This intermediate asymmetric waveguide facilitates the transformation of polarization modes by creating mixed modes with equal horizontal and vertical electric field components. The intermediary structure enables gradual and efficient polarization conversion without significant energy loss, solving the conversion efficiency issue.
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 enhanced polarization mode conversion efficiency, allowing for improved image projection quality in near-eye wearable devices by equalizing horizontal and vertical electric field components, thereby optimizing the conversion process.
Implementation Method 1
a core layer that is provided on the main surface and consists of a material having an electro-optical effect... In a material having an electro-optical effect such as a lithium niobate film, optical characteristics such as an effective refractive index and modulation efficiency vary
Data Source
AI summary
An optical element comprises: a substrate including a main surface; and a core layer that is provided on the main surface. The core layer includes a mode converter that converts a polarization mode of visible light. The mode converter includes: a first waveguide to which the visible light is incident in a first polarization mode that is one polarization mode of a TE mode and a TM mode; a second waveguide that emits the visible light in a second polarization mode that is the other polarization mode of the TE mode and the TM mode; and a third waveguide provided between the first waveguide and the second waveguide, the third waveguide that converts the visible light from the first polarization mode to the second polarization mode. The third waveguide has an asymmetric shape in a second direction along the main surface, the second direction intersecting the first direction.