Optical Mode Converter Structure for Visible-Light Polarization Switching
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Solution Overview
Problem
Existing optical waveguide elements do not effectively convert the polarization mode of visible light, particularly between TM0 and TE0 modes, which is necessary for applications such as laser modules used in near-eye wearable devices.
Innovation Solution
An optical element with a core layer made of a material having an electro-optic effect, featuring a mode converter that includes an incident portion, an emission portion, a first conversion portion, and a second conversion portion. The first conversion portion is asymmetrical in the second direction, allowing conversion between TM0 and TE1 modes, while the second conversion portion is asymmetrical in the third direction, facilitating conversion between TE0 and TE1 modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional optical waveguide element with a simple tapered core is used, then the structure is simple and easy to manufacture, but it cannot effectively convert the polarization mode of visible light between TM0 and TE0 modes
Solution Approach 1:
The mode converter is divided into multiple distinct portions: a first conversion portion for converting between TM0 and TE1 modes, and a second conversion portion for converting between TE0 and TE1 modes. This segmentation allows each portion to be optimized for its specific conversion function, achieving effective visible light polarization mode conversion while maintaining reasonable structural complexity
Solution Approach 2:
The first conversion portion is designed with asymmetry in the second direction (upper and lower tapered portions with different lengths), and the second conversion portion has asymmetry in the third direction. This asymmetry creates the necessary mode coupling conditions for efficient polarization mode conversion in visible light waveguides
Solution Approach 3:
The patent introduces multiple spatial dimensions for mode conversion: the first conversion portion operates with asymmetry in the second direction (vertical dimension), while the second conversion portion operates with asymmetry in the third direction. This multi-dimensional approach enables comprehensive polarization mode conversion that single-dimension designs cannot achieve
2Reliability
If a mode converter with asymmetrical upper and lower tapered portions is used, then polarization mode conversion between TM0 and TE1 is achieved, but the device complexity increases
Solution Approach 1:
Asymmetry is applied locally only where needed for mode conversion (in the upper and lower tapered portions of the first conversion portion), while other parts of the waveguide maintain standard symmetric structures. This localized application of asymmetry achieves the necessary mode coupling without unnecessarily complicating the entire device structure
Solution Approach 2:
The patent applies asymmetry to specific portions (upper and lower tapered portions) rather than the entire waveguide structure. This partial application of asymmetry provides sufficient mode conversion capability while avoiding the excessive complexity that would result from making the entire structure asymmetric
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 element efficiently converts the polarization mode of visible light between TM0 and TE0 modes, reducing light intensity loss and improving conversion efficiency, which is essential for the performance of laser modules in near-eye wearable devices.
Implementation Method 1
a core layer provided on the main surface and made of a material having an electro-optic effect
Data Source
AI summary
In a first region of a first conversion portion, a length of an upper tapered portion in a third direction continuously increases from a first length at a first end to a second length toward an intermediate position, and a length of a lower tapered portion in the third direction continuously increases from the first length at the first end to a third length, which is longer than the second length, toward the intermediate position. In a second region of the first conversion portion, a length of the upper tapered portion in the third direction continuously increases from the second length at the intermediate position to a fourth length, which is shorter than the third length, toward a second end, and a length of the lower tapered portion in the third direction continuously decreases from the third length at the intermediate position to the fourth length toward the second end.