Circular Disc Waveguide Crossing for Low Loss Multi-Mode Signals
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Solution Overview
Problem
Existing waveguide crossings in photonic chips face challenges in achieving low insertion loss and minimal crosstalk while supporting both single mode and multi-mode optical signals across a wide range of wavelengths, particularly in high-density, reconfigurable, and easily fabricable designs.
Innovation Solution
The implementation of a waveguide crossing structure featuring pairs of aligned waveguides with tapering and flaring regions, centered around a circular or slightly elliptical disc, which focuses and redirects optical signals to minimize scattering and crosstalk, and incorporates broadband mode multiplexers to convert higher order modes into fundamental modes for efficient transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional waveguide crossing structures are used, then fabrication is simpler, but insertion loss increases and crosstalk is not minimized
Solution Approach 1:
The patent employs circular disc structures with curved boundaries instead of straight waveguide intersections. The circular discs create smooth curved waveguide paths that reduce scattering and mode coupling at crossings, thereby minimizing insertion loss and crosstalk compared to conventional straight waveguide intersections.
Solution Approach 2:
The patent applies different structural characteristics to different regions: circular discs with specific radii are placed at crossing locations while waveguide sections maintain standard dimensions. The taper regions connect the circular disc sections with different radii, creating localized transitions that minimize disruption to the optical mode while adapting to the circular geometry.
2Adaptability or versatility
If single mode waveguides are used, then crosstalk is reduced, but multi-mode signals cannot be transmitted
Solution Approach 1:
The circular disc waveguide crossing structure is designed to universally support both single-mode and multi-mode optical signals. The circular geometry with carefully selected radius ratios creates mode-matching conditions that work for fundamental modes and higher-order modes alike, allowing the same structure to handle different signal types without significant insertion loss.
Solution Approach 2:
The patent utilizes specific parameter relationships, particularly the ratio between the radius of the circular disc (R) and the waveguide width (W), where R/W is optimized to approximately 0.5-1.0. This parameter optimization ensures that the circular disc structure maintains low insertion loss for both single-mode and multi-mode operations across different wavelengths.
3Adaptability or versatility
If wavelength-specific waveguide crossings are used, then performance is optimized for specific wavelengths, but broadband operation is not achieved
Solution Approach 1:
The circular disc waveguide crossing structure provides universal broadband operation by using geometry-based mode control rather than wavelength-specific features. The circular symmetry and radius ratios create consistent mode-matching conditions across a wide wavelength range, enabling the structure to maintain low insertion loss for both single-mode and multi-mode signals across C-band, L-band, and other optical windows.
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 configuration achieves low insertion loss and minimal crosstalk across various wavelengths, enabling efficient transmission of both single mode and multi-mode optical signals with broadband operation and ease of fabrication, suitable for high-density photonic chip designs.
Implementation Method 1
each of the first and second pairs of aligned waveguides has a first portion that contacts the circular disc at a respective end and tapers along a respective length as the respective waveguide extends towards the circular disc
Implementation Method 2
focuses and redirects optical signals to minimize scattering and crosstalk
Implementation Method 3
a circular disc disposed between the first pair of aligned waveguides and between the second pair of aligned waveguides
Data Source
AI summary
Embodiments herein describe a waveguide crossing that permits at least two optical signals to cross in two different directions. For example, one optical signal can propagate from left to right through the center of the waveguide crossing at the same time a second optical signal propagates up and down through the center of the crossing. In one embodiment, a circular disc is disposed at the center of the waveguide crossing through which the two (or more) optical signals pass. The shape of the circular disc can provide low insertion loss as the respective optical signals propagate between respective pairs of waveguides, as well as minimize cross talk between the two optical signals.