InP Polarization Rotator Geometry for Low-Loss, High-Yield PICs
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Solution Overview
Problem
InP-based PICs face challenges in achieving suitable chip yields due to high fabrication complexity and sensitivity of polarization splitters and rotators, which are not well-suited for CMOS process control, leading to performance and yield issues.
Innovation Solution
A PIC with an InP-based polarization rotator featuring an elongated optical waveguide with specific width profiles and hybridization regions that enable efficient conversion of TM modes to TE modes, using a hybridization length to minimize mode conversion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If InP-based polarization splitters and rotators are used for mode separation and conversion, then coherent reception functionality is achieved, but fabrication complexity and sensitivity increase, leading to reduced chip yields
Solution Approach 1:
The patent combines the polarization splitter and polarization rotator into a single integrated InP-based device structure. The device uses a unified waveguide design with specific geometric parameters to simultaneously achieve mode separation and polarization rotation, eliminating the need for separate components and reducing overall fabrication complexity.
Solution Approach 2:
The invention employs precise control of geometric parameters including waveguide width (w1, w2, w3), height (h1, h2, h3), and length (L) to optimize both the splitting and rotating functions. By carefully selecting these parameters, the device achieves low loss for both TE and TM modes while maintaining compatibility with CMOS process control.
2Reliability
If InP-based polarization rotators with high fabrication precision are used, then mode conversion performance is improved, but manufacturing difficulty increases due to sensitivity to critical dimension variations
Solution Approach 1:
The patent introduces asymmetric waveguide geometry where the waveguide width varies along its length (w1 at input, w2 in middle section, w3 at output) and the height parameters (h1, h2, h3) are deliberately different. This asymmetric design creates specific effective refractive index conditions that enable robust mode conversion while being less sensitive to small manufacturing variations.
Solution Approach 2:
The polarization rotator is divided into multiple sections with different geometric parameters. The waveguide is segmented into regions with varying widths and heights, allowing each section to contribute differently to the overall mode conversion process. This segmentation enables gradual transformation that is more tolerant to fabrication tolerances.
3Adaptability or versatility
If polarization splitting and rotation components are integrated on a single die, then PIC functionality is enhanced, but chip yield decreases due to accumulated fabrication sensitivities
Solution Approach 1:
The patent merges multiple polarization control functions (splitting and rotation) into a single integrated InP-based device, reducing the total number of components that need to be fabricated and assembled on the die. This consolidation reduces the accumulation of fabrication sensitivities and improves overall chip yield.
Solution Approach 2:
The integrated device performs multiple functions simultaneously: it acts as both a polarization splitter and a polarization rotator. This multi-functionality reduces the component count and simplifies the overall PIC architecture, leading to improved manufacturing yields while maintaining enhanced functionality.
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 improved design enhances PIC performance and yield by reducing variations in critical dimensions and supporting low-loss mode conversion, facilitating efficient operation and reducing fabrication complexity.
Implementation Method 1
the first width profile, WP1, and the second width profile, WP2, are configured and arranged to provide the first portion with a hybridization region in which the elongated InP-based optical waveguide has effective refractive index values along a hybridization length, Lh, as seen in a direction parallel to the elongated InP-based optical waveguide, said effective refractive index values enabling a conversion of a lower order TM mode into a higher order TE mode in the hybridization region with a mode conversion loss of at most −10 dB
Data Source
AI summary
A PIC that includes an InP-based polarization rotator having an improved design that enables at least one of an improved performance and an improved yield of the PIC due to at least one of reduced variations in critical dimensions of the InP-based polarization rotator and reduced overlay errors during fabrication of the InP-based polarization rotator of the PIC. An opto-electronic system including said PIC. A method of fabricating the PIC that includes the InP-based polarization rotator having the improved design.