Bent Taper Optical Waveguide for Low-Loss Mode Conversion
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Solution Overview
Problem
Conventional optical waveguide tapers are limited in their ability to efficiently perform mode conversion and polarization rotation, often requiring long lengths and high loss, which hampers their effectiveness in integrated optics applications.
Innovation Solution
A bent taper optical waveguide component with varying waveguide width and angle, configured as a multimode device, capable of efficient mode conversion and polarization rotation, utilizing particle swarm optimization to achieve ultra-high efficiency and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional linear tapers are used for mode conversion, then the device can perform mode conversion function, but the device length becomes too long and loss increases
Solution Approach 1:
The patent applies curvature by transforming the conventional linear taper into a bent taper configuration. The bent taper follows a curved path (circular arc) instead of a straight line, allowing the optical mode to evolve along a curved trajectory. This curvature enables more efficient mode conversion within a shorter physical length, reducing both the device length and associated optical losses while maintaining the mode conversion function.
Solution Approach 2:
The patent introduces a new spatial dimension by bending the taper in a curved configuration rather than maintaining it in a straight linear arrangement. This dimensional change from 1D linear to 2D curved path allows the optical mode to experience gradual transformation along the curved trajectory, achieving effective mode conversion in a more compact footprint with reduced length and loss.
2Ease of operation
If conventional linear tapers are used for polarization rotation, then the device can perform polarization conversion, but the device length becomes too long
Solution Approach 1:
The bent taper configuration with curved geometry enables more efficient polarization rotation by allowing the optical mode to follow a curved propagation path. This curvature facilitates the coupling between different polarization modes (TE and TM modes) through the bent structure, achieving effective polarization rotation in a shorter device length compared to conventional linear tapers.
3Adaptability or versatility
If single mode waveguides are used for waveguide bending, then multimode mixing is avoided, but the device complexity increases and adaptability decreases
Solution Approach 1:
The patent applies local quality by creating a region of varying waveguide width (the tapered section) within the bent waveguide structure. This localized variation in waveguide dimensions along the curved path enables controlled mode conversion and polarization rotation, while the rest of the waveguide maintains a simpler structure. This localized modification provides enhanced adaptability for mode conversion without requiring complete structural complexity throughout the entire device.
Solution Approach 2:
The bent taper structure serves multiple functions simultaneously: it performs mode conversion, polarization rotation, and waveguide bending all within a single integrated component. This multi-functionality increases adaptability, allowing the same structure to handle various optical operations without requiring separate dedicated components for each function, thereby reducing overall device complexity.
Data Source
AI summary
A SOI bent taper structure is used as a mode convertor. By tuning the widths of the bent taper and the bend angles, almost lossless mode conversion is realized between TE0 and TE1 in a silicon waveguide. The simulated loss is <0.05 dB across C-band. This bent taper can be combined with bi-layer TM0-TE1 rotator to reach very high efficient TM0-TE0 polarization rotator. An ultra-compact (9 μm) bi-layer TM0-TE1 taper based on particle swarm optimization is demonstrated. The entire TM0-TE0 rotator has a loss <0.25 dB and polarization extinction ratio >25 dB, worst-case across the C-band.