Asymmetric Waveguide Taper for Polarization Conversion
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Solution Overview
Problem
Existing optical circuit elements with asymmetric directional couplers have low tolerance for manufacturing errors, leading to decreased conversion efficiency and intensity of output light due to deviations in waveguide width, resulting in deteriorated transmission characteristics and polarization extinction ratio.
Innovation Solution
The optical circuit element design includes waveguides with varying widths along the light propagation direction, incorporating a coupled waveguide and a tapered waveguide structure to minimize the difference in effective refractive indices between TE1 and TE0 modes, thereby increasing tolerance for manufacturing errors and maintaining high conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a vertically asymmetric core structure with different widths for upper and lower cores is used to perform higher-order polarization conversion, then polarization conversion between TE1 mode and TM0 mode is achieved, but the structure becomes sensitive to manufacturing errors in waveguide width
Solution Approach 1:
The patent applies dynamics by making the waveguide width variable along the propagation direction rather than fixed. The second segment and coupled waveguide have widths that change gradually, allowing the structure to adapt to manufacturing variations dynamically. This dynamic width adjustment compensates for manufacturing errors while maintaining the polarization conversion function.
Solution Approach 2:
The patent changes the geometric parameter (waveguide width) from a fixed value to a variable function of position. By designing the width to change along the propagation direction, the effective refractive indices for different modes are adjusted, creating a tolerance mechanism that absorbs manufacturing errors without compromising polarization conversion performance.
2Ease of manufacture
If fixed width waveguides are used in the asymmetric directional coupler, then the structure is simple to manufacture, but conversion efficiency decreases due to manufacturing error deviations
Solution Approach 1:
The patent transitions from static (fixed width) to dynamic (variable width) waveguide structures. The gradual width change in the second segment and coupled waveguide allows the system to maintain high conversion efficiency despite manufacturing variations, effectively resolving the trade-off between manufacturing simplicity and conversion efficiency.
Solution Approach 2:
The patent implements beforehand cushioning by designing the width variation profile in advance to compensate for expected manufacturing errors. The gradual width change acts as a pre-built tolerance mechanism that cushions against deviations before they can affect conversion efficiency, ensuring stable performance.
3Manufacturing precision
If the waveguide width is made variable along the propagation direction, then tolerance for manufacturing errors is increased, but the device complexity increases
Solution Approach 1:
The patent applies local quality by making only the specific regions (second segment and coupled waveguide) have variable width, while other parts of the waveguide maintain fixed dimensions. This localized approach provides the necessary tolerance mechanism without unnecessarily complicating the entire device structure.
Solution Approach 2:
The patent introduces dynamic width variation only where needed for tolerance compensation, keeping the overall device structure relatively simple. The gradual width change in specific segments provides manufacturing robustness without requiring complex control systems or additional components.
4Adaptability or versatility
If manufacturing errors cause deviations in waveguide width, then production becomes more flexible, but transmission characteristics and polarization extinction ratio deteriorate
Solution Approach 1:
The patent uses parameter changes by designing the waveguide width as a position-dependent function that compensates for manufacturing variations. This allows the structure to maintain stable transmission characteristics and polarization extinction ratio while accommodating flexible manufacturing tolerances.
Solution Approach 2:
The patent implements a passive feedback mechanism where the variable width profile automatically adjusts the effective refractive indices based on the actual waveguide dimensions. This inherent feedback compensates for manufacturing errors without requiring active control, maintaining reliable transmission characteristics.
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 design enhances the tolerance for manufacturing errors, stabilizes the conversion efficiency between TE1 and TE0 modes, and improves the polarization extinction ratio, ensuring consistent and high-quality output light transmission.
Implementation Method 1
minimize the difference in effective refractive indices between TE1 and TE0 modes
Implementation Method 2
conversion efficiency between TE1 and TE0 modes
Data Source
AI summary
An optical circuit element formed on a substrate, the optical circuit element includes a first waveguide and a second waveguide, the second waveguide having a shape in a width direction, the shape being asymmetrical to the first waveguide. The first waveguide includes a first segment and a second segment, the first segment having a width that changes along a light propagation direction, the second segment continuous with the first segment. The second waveguide includes a coupled waveguide adjacent to the second segment of the first waveguide. At least one of the second segment and the coupled waveguide has a shape with a width that changes along the light propagation direction.