Curved Echelle Grating Shadow Facets Reduce Back Reflection

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Solution Overview

Problem

Optical multiplexers and demultiplexers using echelle gratings suffer from high back reflection, leading to laser instability and noise interference in transmitters and receivers, respectively, due to coherent interactions with on-chip reflected light, which degrades bit error rate and transmitter performance.

Innovation Solution

A curved echelle grating with angled shadow facets is implemented on a silicon-on-insulator platform, where the shadow facets are angled greater than 0 degrees but less than 60 degrees relative to the normal of the curved grating, preventing back reflection and reducing interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If legacy total internal reflection echelle grating is used, then compact size and integration ability are achieved, but back reflection of light increases causing laser instability and noise

Engineering Contradiction:

Improveintegration abilityVSAvoidlaser stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies asymmetry by introducing a shadow facet with a specific angle (greater than 0 degrees but less than 60 degrees) relative to the grating facet. This asymmetric configuration causes reflected light to be directed away from the laser source, preventing back reflection while maintaining the compact integrated structure. The shadow facet creates an angular deviation that asymmetrically redirects light paths to eliminate harmful interference.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent converts the harmful back reflection into a beneficial directional reflection. By designing the shadow facet at a specific angle, the light that would normally reflect back to cause instability is instead redirected at an angle that excludes it from the laser cavity. This transforms the harmful reflective property into a useful directional control mechanism that maintains laser stability.

Inventive Principle:

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

2Device complexity

If echelle grating is used for multiplexing and demultiplexing, then compact size is achieved, but multi-path interference effect generates additional noise at receiver

Engineering Contradiction:

Improvecompact sizeVSAvoidnoise at receiver

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The asymmetric shadow facet configuration redirects reflected light away from the receiver path, preventing multi-path interference. The specific angle of the shadow facet ensures that reflected beams do not re-enter the receiver, eliminating the coherent interference that generates noise while preserving the compact grating structure.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent converts the potentially harmful multi-path interference into a beneficial directional separation. The shadow facet angles reflected light into paths that do not intersect with the receiver, transforming what would be interfering noise paths into excluded directional paths, thereby reducing noise at the receiver.

Inventive Principle:

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

3Reliability

If shadow facet angle is increased to prevent back reflection, then laser stability improves, but grating efficiency may decrease

Engineering Contradiction:

Improvelaser stabilityVSAvoidgrating efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent optimizes the shadow facet angle parameter within a specific range (greater than 0 degrees but less than 60 degrees) to balance two competing requirements: preventing back reflection to maintain laser stability and maintaining sufficient grating efficiency for effective multiplexing/demultiplexing. This parameter optimization ensures both stability and efficiency are achieved simultaneously.

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 increases the efficiency of optical apparatuses by minimizing back reflection, enhancing laser stability and reducing noise interference, thereby improving bit error rate and transmitter performance.

Implementation Method 1

echelle grating based on the total internal reflection principle

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

the shadow facets are angled greater than 0 degrees but less than 60 degrees relative to the normal of the curved grating, preventing back reflection

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 3

echelle grating with a plurality of grating teeth

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS10197737B2Low back reflection echelle grating

Publication Date: 2019.02.05 INTEL CORP

AI summary

Embodiments of the present disclosure are directed toward an optical apparatus that includes a semiconductor layer to propagate light from at least one light source. The optical apparatus may further include a curved echelle grating with a plurality of grating teeth, the echelle grating at an outer side of the semiconductor layer. The curved echelle grating may include a plurality of grating teeth, and a grating tooth of the plurality of grating teeth may have a grating facet and a shadow facet. A shadow facet may have an angle of grating greater than 0 degrees with respect to a normal of a curve of the curved echelle grating. Other embodiments may be described and/or claimed.