2D Elliptical Grating Coupler for Low Polarization Loss

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional polarization splitting grating couplers (PSGCs) suffer from high polarization dependent loss (PDL) due to non-zero fiber angles, leading to inefficient light coupling between waveguides and optical fibers.

Innovation Solution

A two-dimensional (2D) grating coupler design with elliptical grating lines and concave polygon scattering elements, configured to improve mode field matching and reduce PDL, utilizing a combination of taper structures and scattering elements with varying sizes and shapes to handle arbitrary polarization states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional PSGC with circular or square scattering elements is used, then polarization splitting function is achieved, but polarization dependent loss between TE and TM modes increases

Engineering Contradiction:

Improvepolarization splitting functionVSAvoidpolarization dependent loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent employs asymmetric scattering elements with different geometries (e.g., rectangular, triangular, or circular shapes) positioned at specific locations within the grating structure. These asymmetric elements create different scattering patterns for TE and TM polarized light, enabling polarization splitting while controlling polarization dependent loss through careful geometric design and positioning.

Inventive Principle:

Principle #4Asymmetry

2Object-generated harmful factors

If non-zero fiber angle is used to minimize reflections, then reflection at the interface is reduced, but polarization dependent loss increases

Engineering Contradiction:

Improvereflection lossVSAvoidpolarization dependent loss

Core Design Contradiction:

Object-generated harmful factorsVSLoss of energy

Solution Approach 1:

The patent implements local quality variations by positioning scattering elements with specific geometric properties at different locations within the grating structure. Elements near the fiber interface are designed with characteristics optimized for reflection minimization, while elements deeper in the structure are optimized for polarization splitting, thereby achieving both goals simultaneously with reduced polarization dependent loss.

Inventive Principle:

Principle #3Local quality

3Productivity

If scattering elements are placed at the intersection of grating lines, then grating coupling function is enhanced, but polarization dependent loss increases

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidpolarization dependent loss

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent divides the grating structure into multiple regions with different scattering element configurations. By segmenting the grating into zones with varying element densities, shapes, and orientations, the design achieves effective polarization splitting and mode field matching while controlling polarization dependent loss through spatially distributed scattering mechanisms.

Inventive Principle:

Principle #1Segmentation

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

Enhances light coupling efficiency by minimizing polarization dependent loss and improving mode field matching, thereby optimizing the transfer of optical signals between waveguides and optical fibers.

Implementation Method 1

Optical gratings are frequently used to couple light between a waveguide and an optical fiber

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a polarization splitting grating coupler (PSGC) is needed to provide polarization light in either transverse magnetic (TM) or transverse magnetic (TE) polarization mode from the optical fiber to the waveguide

Methodology Applied

Scientific EffectScattering: Scattering

Data Source

PatentUS12578539B2Optical coupling apparatus and methods of making same

Publication Date: 2026.03.17 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Disclosed are apparatus and methods for optical coupling in optical communications. In one embodiment, an apparatus for optical coupling is disclosed. The apparatus includes: a planar layer; an array of scattering elements arranged in the planar layer at a plurality of intersections of a first set of concentric elliptical curves crossing with a second set of concentric elliptical curves rotated proximately 90 degrees to form a two-dimensional (2D) grating; a first taper structure formed in the planar layer connecting a first convex side of the 2D grating to a first waveguide; and a second taper structure formed in the planar layer connecting a second convex side of the 2D grating to a second waveguide. Each scattering element is a pillar into the planar layer. The pillar has a top surface whose shape is a concave polygon having at least 6 corners.