Semiconductor Grating Coupler with Embedded Metal Layer
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Solution Overview
Problem
Existing grating couplers in optical transceiver modules face inefficiencies due to optical fiber input tunneling through the semiconductor layer, compromising coupling efficiency.
Innovation Solution
A two-dimensional grating coupler design with scattering elements arranged in an apodized structure and a metal layer embedded between the semiconductor and dielectric layers to reflect tunneled optical signals, improving coupling efficiency by enhancing mode field matching and reducing polarization-dependent loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional grating coupler structure is used, then the device complexity is low, but the coupling efficiency deteriorates due to optical tunneling through the semiconductor layer
Solution Approach 1:
The grating coupler is segmented into multiple scattering elements arranged in a two-dimensional pattern with varying dimensions and spacing. This segmentation creates different optical path lengths and phase delays, enabling constructive interference for the desired mode while reducing tunneling effects and improving coupling efficiency to the optical fiber.
Solution Approach 2:
The scattering elements exhibit local quality variations through apodization, where the dimensions, spacing, and depth of individual scattering elements are locally optimized. This creates a gradient in scattering strength across the grating structure, enhancing mode field matching at specific locations while maintaining overall coupling efficiency and reducing polarization-dependent loss.
2Reliability
If the semiconductor layer thickness is reduced to improve coupling, then the tunneling effect worsens and compromises signal integrity
Solution Approach 1:
The grating structure is designed to preemptively counteract the tunneling effect by creating destructive interference for tunneling modes through carefully engineered scattering elements. The apodized pattern of scattering elements generates phase differences that cancel out tunneling signals before they can compromise signal integrity, allowing the semiconductor layer to maintain its protective thickness.
3Reliability
If a simple grating pattern is used, then the manufacturing precision requirement is low, but the polarization-dependent loss increases
Solution Approach 1:
The scattering elements are designed with asymmetric dimensions and orientations to differentially interact with orthogonal polarization modes. This asymmetry, combined with the two-dimensional apodized pattern, creates complementary scattering effects that balance the response for both polarizations, thereby reducing polarization-dependent loss while maintaining manufacturability through standard fabrication tolerances.
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 solution significantly enhances light coupling efficiency and reduces polarization crosstalk, optimizing the performance of optical transceiver modules for high-speed optical communication systems.
Implementation Method 1
a metal layer embedded between the semiconductor and dielectric layers to reflect tunneled optical signals
Implementation Method 2
A two-dimensional grating coupler design with scattering elements arranged in an apodized structure
Implementation Method 3
scattering elements arranged in an apodized structure
Data Source
AI summary
A semiconductor structure includes a substrate and a metal layer disposed in the substrate. The semiconductor structure includes a dielectric layer disposed over the metal layer. The semiconductor structure further includes a semiconductor layer disposed over the dielectric layer, where the metal layer extends across the semiconductor layer. The semiconductor layer includes a two-dimensional grating coupler including a plurality of scattering elements disposed in the semiconductor layer and a pair of tapered structures extending laterally from the two-dimensional grating coupler.