Grating Coupler Index Gradient for Lower Back Reflection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Optical gratings exhibit poor coupling efficiency, with a significant portion of redirected light not reaching the optical detector, leading to inefficient communication between light sources and other components.

Innovation Solution

A grating coupler design with a core layer featuring a gradual decrease in effective refractive index and optimized hole arrangements in the optical coupling region, combined with adjustable optical fiber angles, to enhance coupling efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If optical gratings are used to redirect light from optical fiber to optical detector, then light coupling is enabled, but coupling efficiency is poor with large part of redirected light not reaching the detector

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidlight transmission reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies local quality by creating a graded index structure where the refractive index varies spatially within the optical grating. The core layer has a different refractive index profile than the cladding layers, with the core index decreasing from bottom to top. This localized variation in optical properties optimizes light coupling at specific regions while maintaining overall grating functionality.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs parameter changes by systematically varying the refractive index parameter throughout the grating structure. The effective refractive index of the core layer gradually decreases from the bottom to the top, and the cladding layers have progressively increasing refractive indices. This parameter gradient transforms the light propagation characteristics to improve coupling efficiency.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If light travels transversely through optical gratings by reflecting off inner surfaces at shallow angles, then light redirection is achieved, but back reflection occurs reducing coupling efficiency

Engineering Contradiction:

Improvelight redirection capabilityVSAvoidback reflection loss

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent converts the harmful back reflection into a beneficial effect by designing the graded index structure to control and redirect reflected light. The varying refractive index profile causes light to gradually change direction, transforming what would be harmful back reflections into useful forward-propagating modes that contribute to coupling efficiency.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent addresses back reflection by introducing a vertical dimension to the refractive index variation. Instead of uniform lateral structures, the refractive index changes through the thickness of the grating, creating a three-dimensional optical control mechanism that manages light propagation in multiple dimensions and reduces harmful reflections.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Improves coupling efficiency by reducing back reflection and aligning optical signals optimally, achieving efficiencies up to 50% for wavelengths around 1290 nm.

Implementation Method 1

An effective refractive index of the core layer gradually decrease from a first end of the optical coupling region to a second end of the optical coupling region

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

Improves coupling efficiency by reducing back reflection

Methodology Applied

Scientific EffectBack reflection reduction: Reflection

Implementation Method 3

at least one grating coupler in the at least one trench for transmitting optical signals between the semiconductor photonic die and the optical fiber array

Methodology Applied

Scientific EffectOptical coupling: Diffraction

Data Source

PatentUS12529844B2Apparatus for optical coupling

Publication Date: 2026.01.20 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Disclosed are apparatuses for optical coupling and a system for communication. In one embodiment, an apparatus for optical coupling having an optical coupling region is disclosed. The apparatus for optical coupling includes a substrate and a core layer disposed on the substrate. The core layer includes a plurality of holes located in the optical coupling region. An effective refractive index of the core layer gradually decrease from a first end of the optical coupling region to a second end of the optical coupling region.