Spiral Waveguide Absorbers with Grating Patterns
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Solution Overview
Problem
Semiconductor optical waveguide structures face issues with optical signal leakage and crosstalk due to high optical return loss from Ge absorbers, leading to instability and increased bit-error-rate in communication links.
Innovation Solution
The implementation of ultra-compact subwavelength waveguide absorbers with a spiral configuration and grating patterns, made from silicon or silicon nitride, which efficiently absorb incoming light with minimized back reflection, reducing the need for Ge material and integrating seamlessly with existing fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ge absorbers are used to prevent optical signal leakage, then signal containment is improved, but optical return loss increases causing back-reflection and backscatter
Solution Approach 1:
The patent changes the material parameter from Ge to silicon or silicon nitride, and modifies the structural parameter by introducing a grating pattern with specific pitch and depth parameters. This combination achieves both signal containment and reduced optical return loss by controlling the interaction between light and the absorber structure through carefully selected material and geometric parameters.
Solution Approach 2:
The grating pattern creates a porous-like structure with periodic voids that allow controlled light interaction. The grating geometry (pitch, depth, duty cycle) enables the absorber to maintain signal containment while reducing back-reflection by providing multiple scattering paths and reducing the abruptness of the material interface.
2Reliability
If Ge absorbers are used to prevent crosstalk, then signal isolation is improved, but manufacturing complexity increases due to additional material integration steps
Solution Approach 1:
The patent uses silicon or silicon nitride materials that are homogeneous with the existing semiconductor waveguide structures. This material compatibility eliminates the need for separate Ge material integration processes, allowing the absorber to be manufactured using the same fabrication steps already employed for the photonic devices, thereby maintaining signal isolation while simplifying manufacturing.
3Loss of energy
If conventional absorbers are used, then signal absorption is achieved, but device footprint is large
Solution Approach 1:
The continuous absorber structure is segmented into a grating pattern with periodic discontinuities. This segmentation increases the effective absorption per unit area by creating multiple interaction zones, allowing the same absorption performance to be achieved in a smaller footprint. The grating periods are designed to be subwavelength to maintain effective absorption while reducing the overall area.
Solution Approach 2:
The patent transitions from a planar absorber design to a three-dimensional grating structure with vertical depth components. This dimensional addition allows the absorber to interact with light over a larger effective area within the same footprint, improving absorption efficiency without increasing the lateral device area.
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 spiral waveguide absorbers with grating patterns significantly reduce back reflection and radiation losses, achieving improved signal integrity and a smaller footprint compared to Ge-based absorbers, with back reflection as low as -43 dB and insertion loss of 63 dB, while maintaining compatibility with known process flows.
Implementation Method 1
an absorber is coupled to the open or unconnected ports or other termination points of the photonics device
Implementation Method 2
The absorbers are known to be manufactured from Ge material as they are easily integrated into the fabrication processes of the photonics devices
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to spiral waveguide absorbers and methods of manufacture. The structure includes: a photonics component; and a waveguide absorber with a grating pattern coupled to a node of the photonics component.