High-Order-Mode Filter for Silicon Waveguides

Solution Overview

Problem

Optical waveguides with thick silicon faces challenges in filtering higher-order modes without affecting the fundamental mode, as large bends required to prevent loss of the fundamental mode result in increased attenuation and larger chip footprints.

Innovation Solution

An optical filter design featuring a shoulder slab and two filter ridges separated from a waveguide ridge, where the fundamental mode is guided while higher-order modes are attenuated, minimizing loss and footprint through a compact structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If large bends are used to prevent loss of the fundamental mode, then the fundamental mode transmission is improved, but the attenuation of higher-order modes increases and the chip footprint enlarges

Engineering Contradiction:

Improvefundamental mode transmissionVSAvoidattenuation of higher-order modes

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The filter structure is segmented into multiple ridges (first ridge, second ridge, third ridge) positioned at different locations and orientations. Each ridge segment contributes to filtering higher-order modes through cumulative effect, allowing effective attenuation without requiring large bend radii that would increase footprint and fundamental mode loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different ridges are positioned with specific local geometries and orientations optimized for their local function. The first ridge has a first orientation, the second ridge has a second orientation, and the third ridge has a third orientation, creating locally optimized filtering zones that collectively achieve high-order mode attenuation while preserving fundamental mode transmission.

Inventive Principle:

Principle #3Local quality

2Reliability

If large bends are used to prevent loss of the fundamental mode, then the fundamental mode transmission is improved, but the chip footprint enlarges

Engineering Contradiction:

Improvefundamental mode transmissionVSAvoidchip footprint

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The filter structure is segmented into multiple ridges (first ridge, second ridge, third ridge) positioned at different locations and orientations. Each ridge segment contributes to filtering higher-order modes through cumulative effect, allowing effective attenuation without requiring large bend radii that would increase footprint and fundamental mode loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using large bends in the propagation direction (one dimension), the solution uses multiple ridges with different orientations arranged in a multi-dimensional configuration. This approach achieves filtering functionality by utilizing spatial arrangement in multiple dimensions rather than relying on large-scale bending in a single dimension, thereby reducing chip footprint.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Loss of energy

If conventional filtering structures are used, then higher-order modes are attenuated, but the fundamental mode experiences increased loss

Engineering Contradiction:

Improveattenuation of higher-order modesVSAvoidfundamental mode transmission

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

Different ridges are positioned with specific local geometries and orientations optimized for their local function. The first ridge has a first orientation, the second ridge has a second orientation, and the third ridge has a third orientation, creating locally optimized filtering zones that collectively achieve high-order mode attenuation while preserving fundamental mode transmission.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The filter structure utilizes specific parameter configurations including ridge heights (first height, second height, third height), ridge spacing (first gap, second gap), and ridge orientations (first orientation, second orientation, third orientation). These parameters are optimized to create selective filtering that attenuates higher-order modes while maintaining fundamental mode transmission with minimal loss.

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

The optical filter effectively attenuates higher-order modes with minimal loss of the fundamental mode, achieving greater than 9 dB attenuation and reducing reflections, thereby enhancing the performance of optical devices.

Implementation Method 1

An optical waveguide directs radiation in the visible, infrared, and/or ultra-violet portions of the radiation spectrum by total internal reflection

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

Optical waveguiding elements convey light from one point to another through an optically transparent, elongated structure by modal transmission, total internal reflection, and/or total reflectorization

Methodology Applied

Scientific EffectModal transmission:

Data Source

PatentUS9465163B2High-order-mode filter for semiconductor waveguides

Publication Date: 2016.10.11 SKORPIOS TECHNOLOGIES INC

AI summary

A high-order-mode (HOM) filter for thick silicon waveguides has a shoulder slab, a waveguide ridge, a first filter ridge, and a second filter ridge. The first filter ridge and the second filter ridge help attenuate higher-order modes from the waveguide ridge while the waveguide ridge guides a fundamental mode.