Stagger-Tuned Grating Couplers for Wide-Bandwidth Silicon Photonics

Solution Overview

Problem

Conventional grating couplers in silicon photonics face challenges in achieving high coupling efficiency over a wide bandwidth while maintaining low reflection and optimal angle alignment, leading to increased complexity and cost in photonic chip packaging, and are sensitive to fabrication inaccuracies and environmental changes.

Innovation Solution

The development of stagger-tuned grating couplers, which utilize a single-etch layer with differently tuned sections to scatter light at varying angles, allowing for effective coupling over a wider bandwidth without additional components or complex designs, thereby reducing sensitivity to fabrication tolerances and environmental fluctuations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional single-etch grating designs are used, then fabrication is simple, but coupling efficiency is limited and bandwidth is narrow

Engineering Contradiction:

Improvefabrication simplicityVSAvoidcoupling efficiency

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The grating coupler is divided into multiple sections along the propagation direction, with each section having a distinct etch depth. This segmentation allows different portions of the grating to contribute to different wavelength ranges, thereby expanding the overall bandwidth while maintaining fabrication simplicity through a single-etch process that creates the depth variations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the grating coupler are assigned different local properties (etch depths) to optimize performance for specific wavelength ranges. The first section has a first etch depth optimized for a first wavelength range, while the second section has a second etch depth optimized for a second wavelength range, allowing each local region to contribute its optimal performance characteristics

Inventive Principle:

Principle #3Local quality

2Reliability

If conventional grating couplers are designed for narrow bandwidth, then coupling efficiency at specific wavelength is high, but bandwidth is limited

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidbandwidth

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The grating coupler is divided into multiple sections along the propagation direction, with each section having a distinct etch depth. This segmentation allows different portions of the grating to contribute to different wavelength ranges, thereby expanding the overall bandwidth while maintaining fabrication simplicity through a single-etch process that creates the depth variations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The etch depth parameter is varied across different sections of the grating coupler to achieve broadband operation. By changing the etch depth from a first depth in the first section to a second depth in the second section, the device maintains high coupling efficiency across multiple wavelength ranges, effectively expanding the operational bandwidth

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If additional components are added to expand bandwidth, then bandwidth increases, but device complexity increases

Engineering Contradiction:

ImprovebandwidthVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple functional sections with different etch depths are merged into a single integrated grating coupler structure. This combining approach achieves broadband operation by integrating the wavelength-selective functionality of multiple gratings into one device, eliminating the need for separate components and reducing overall device complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The grating coupler is designed to perform multiple functions within a single device structure. By incorporating sections with different etch depths, the device can couple light across multiple wavelength ranges simultaneously, making it a universal coupler that replaces what would traditionally require multiple separate components

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Device complexity

If conventional grating couplers are used, then design is simple, but sensitivity to fabrication errors and environmental changes is high

Engineering Contradiction:

Improvedesign simplicityVSAvoidsensitivity to fabrication errors

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The grating coupler is divided into multiple sections along the propagation direction, with each section having a distinct etch depth. This segmentation allows different portions of the grating to contribute to different wavelength ranges, thereby expanding the overall bandwidth while maintaining fabrication simplicity through a single-etch process that creates the depth variations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The etch depth parameter is varied across different sections of the grating coupler to achieve broadband operation. By changing the etch depth from a first depth in the first section to a second depth in the second section, the device maintains high coupling efficiency across multiple wavelength ranges, effectively expanding the operational bandwidth

Inventive Principle:

Principle #35Parameter changes

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 enables high coupling efficiency over a wide bandwidth with reduced sensitivity to fabrication errors and environmental changes, simplifying the design and reducing the complexity of photonic chip packaging, making it suitable for applications like CWDM.

Implementation Method 1

Grating couplers are micro-scale passive devices that can efficiently convert a guided wave in a waveguide to a largely unidirectional output beam of a desired mode shape via the constructive interference of periodically etched trenches (or scatterers)

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

Grating couplers are micro-scale passive devices that can efficiently convert a guided wave in a waveguide to a largely unidirectional output beam of a desired mode shape via the constructive interference of periodically etched trenches (or scatterers)

Methodology Applied

Scientific EffectConstructive interference: Interference

Data Source

PatentUS10884192B1Single-etch wide-bandwidth grating couplers with individually-tuned grating sections

Publication Date: 2021.01.05 HEWLETT PACKARD ENTERPRISE DEV LP

AI summary

Examples herein relate to single-etch layer grating couplers. In particular, implementations herein relate to single-etch layer grating couplers comprising a planar waveguide wherein a first grating section and a second grating section are etched into. The first grating section is configured to scatter light at a given wavelength at a first angle relative to vertical and the second grating section is configured to scatter light at the given wavelength at a second angle relative to vertical. The stagger-tuning of the first grating section and the second grating section results in the light at the given wavelength being scattered at a desired angle the same or near an angle at which an optical fiber is offset from vertical.