Polarization Diversity Grating Coupler with Segmented Scatterers
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Solution Overview
Problem
Conventional polarization diversity grating couplers face challenges in achieving low loss and zero polarization-dependent wavelength (PDW) and polarization-dependent loss (PDL) due to limitations in optimizing design parameters, particularly in coupling light between optical fibers and photonic integrated circuits.
Innovation Solution
The implementation of a polarization diversity grating coupler architecture with multiple scattering regions, each with tailored scattering strengths and polarization-dependent wavelengths, optimized using an adjoint method to quickly search through a large parameter space, ensuring an increasing scattering strength as light traverses the coupler and is coupled into the optical fiber, while employing advanced numerical techniques and scatterer shape designs to minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional polarization diversity grating coupler designs are used, then the device can couple light between optical fibers and waveguides, but the loss is high and PDW/PDL cannot be reduced to zero
Solution Approach 1:
The grating coupler is divided into multiple scattering regions with different scattering strengths. Each region is independently optimized to control the scattering of light with different polarization states, enabling separate optimization of S-polarization and P-polarization coupling paths to achieve low loss and zero PDW/PDL
Solution Approach 2:
Different regions of the grating are assigned different local properties (scattering strengths) tailored to specific polarization states. The scattering strength varies spatially across the grating structure, with each region optimized for its local polarization coupling requirements, achieving both low overall loss and zero polarization-dependent wavelength and loss
2Reliability
If the parameter space is extensively optimized to reduce PDW and PDL, then polarization-dependent effects improve, but the design and manufacturing complexity increases
Solution Approach 1:
The invention systematically varies key parameters including scatterer shapes (circular, square, rectangular, triangular, dendritic), sizes, spacing, and distribution patterns across different regions. This parameter optimization is performed separately for S-polarization and P-polarization, enabling independent tuning to achieve zero PDW/PDL while maintaining manufacturable design specifications
3Productivity
If scattering strength is increased to improve coupling efficiency, then more light is coupled into the fiber, but polarization-dependent effects increase
Solution Approach 1:
The grating is segmented into multiple regions with progressively increasing scattering strengths from the input side toward the output side. This segmentation allows different regions to handle different polarization states differently, increasing overall coupling efficiency while maintaining polarization independence through balanced design of S and P polarization paths
Solution Approach 2:
Each scattering region is assigned a local scattering strength optimized for its position in the light propagation path. Regions closer to the input have lower scattering strength while regions closer to the output have higher scattering strength, with each region's properties independently optimized for both S and P polarizations to maintain polarization independence while maximizing coupling efficiency
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 approach results in low loss and near-zero PDW and PDL, effectively improving the coupling efficiency and reducing polarization-dependent effects, enhancing the performance of optical systems in high-speed computing and communication applications.
Implementation Method 1
a first plurality of scatterer structures dimensioned to provide a first scattering strength... a second plurality of scatterer structures dimensioned to provide a second scattering strength
Data Source
AI summary
An optical grating coupler defining an axis and configured to couple light between a planar waveguide and an optical fiber, including first and second entry surfaces and a plurality of scattering regions symmetric to the axis and arranged such scattering strength presented to incoming light by the plurality of scattering regions changes from weak to strong along a beam path of the incoming light to match a Gaussian mode profile of the optical fiber.