Grating Coupler Tapered Waveguide O-band CWDM

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Solution Overview

Problem

Current grating couplers face challenges in achieving high efficiency and broadband operation for optical signal redirection, particularly in the O-band CWDM wavelength window, due to limitations in coupling loss and bandwidth.

Innovation Solution

The implementation of a thickness-tapered waveguide structure with a grating layer perpendicular to the direction of tapering, combined with thin-film layers above and below the waveguide layer, enhances coupling efficiency and bandwidth by improving light collection from different angles and providing phase-matching conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional grating coupler structure is used, then the device complexity is low, but the coupling efficiency is insufficient and bandwidth is limited

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidwaveguide structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The waveguide layer is segmented into multiple sections with different thicknesses (tapered structure), where each section contributes to different aspects of light coupling. The grating structure is divided into multiple periods with varying geometries, allowing independent optimization of coupling efficiency and bandwidth characteristics

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces vertical dimensionality by implementing a thickness-tapered waveguide structure where the waveguide thickness varies along the propagation direction. This adds a vertical gradient dimension to the traditionally planar grating coupler, enabling enhanced mode matching and broader bandwidth operation

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If the grating coupler is designed for high efficiency, then coupling loss is reduced, but the bandwidth is limited

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidbandwidth

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

Different sections of the grating coupler are assigned different local properties: the tapered waveguide sections provide gradual mode transformation for high efficiency, while specific grating periods are optimized for different wavelength ranges to expand bandwidth. The structure exhibits spatially varying characteristics that simultaneously address efficiency and bandwidth requirements

Inventive Principle:

Principle #3Local quality

3Reliability

If a thickness-tapered waveguide structure with multiple layers is implemented, then coupling efficiency and bandwidth are enhanced, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidlayer thickness precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention employs continuous parameter variation in the waveguide thickness taper rather than discrete step changes. This gradual transition reduces sensitivity to manufacturing tolerances while maintaining the beneficial effects of the tapered structure for enhanced coupling efficiency and 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 configuration results in a peak coupling loss of approximately 0.69 dB with a 1 dB bandwidth of 83 nm, achieving a flat-top spectrum response and improved light redirection within the O-band CWDM window.

Implementation Method 1

The grating facilitates redirection of light to or from a waveguide. For example, light from the waveguide may be redirected to a fiber, or light from the fiber may be redirected to the waveguide.

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

Methodology Applied

Scientific EffectPhase matching:

Data Source

PatentUS11754784B2Grating coupler

Publication Date: 2023.09.12 CISCO TECHNOLOGY INC

AI summary

Embodiments presented in this disclosure generally relate to an optical device having a grating coupler for redirection of optical signals. One embodiment includes a grating coupler. The grating coupler generally includes a waveguide layer, a thickness of a waveguide layer portion of the waveguide layer being tapered, the thickness defining a direction, and a grating layer disposed above the waveguide layer and perpendicular to the direction where at least a grating layer portion of the grating layer overlaps the waveguide layer portion of the waveguide layer along the direction. Some embodiments are directed to grating coupler implemented with material layers above and a reflector layer below a grating layer, facilitating redirection and confinement of light that improves coupling loss and bandwidth. The material layers and reflector layer above and below the grating layer may be implemented with or without the waveguide layer being tapered.