Silicon Photonics Package Structure with Lens and Isolator

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Solution Overview

Problem

The coupling efficiency between distributed feedback lasers (DFB-LD) and silicon photonic integrated circuits (Si PIC) edge couplers is limited by mode size mismatch, leading to high coupling loss and return loss issues, particularly in QSFP form factors, which restricts the spectral bandwidth and compatibility with data center applications.

Innovation Solution

A compact and efficient coupling structure is implemented using a DFB-LD, Si PIC with edge couplers, a silica cover lid, a lens to minimize spot size mismatch, and an isolator with index matching fluid and anti-reflection coating to reduce return loss, along with a single-mode fiber aligned to the output edge coupler.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a lens is added to minimize mode size mismatch, then coupling efficiency is improved, but device complexity increases

Engineering Contradiction:

Improvecoupling lossVSAvoidcoupling structure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent introduces a lens as an intermediary component between the DFB-LD and the edge coupler to mediate the mode size mismatch. The lens transforms the beam profile to match between the laser and coupler, serving as a mediator that enables efficient coupling without directly modifying the DFB-LD or edge coupler structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The coupling system is segmented into distinct functional components: the DFB-LD, the lens, and the edge coupler. This segmentation allows each component to be optimized independently - the DFB-LD for laser emission, the lens for beam transformation, and the edge coupler for fiber coupling - while maintaining overall system performance.

Inventive Principle:

Principle #1Segmentation

2Reliability

If an isolator is added to suppress return loss, then laser stability is improved, but device complexity increases

Engineering Contradiction:

Improvelaser stabilityVSAvoidcoupling structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent converts the harmful effect of reflected light (return loss) into a beneficial outcome by using the isolator to block reflections while allowing forward propagation. The isolator transforms the potential harm of reflections into a controlled situation where reflections are eliminated, improving laser stability without compromising the coupling efficiency.

Inventive Principle:

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

3Adaptability or versatility

If edge coupler is used instead of grating coupler, then spectral bandwidth is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvespectral bandwidthVSAvoidalignment precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent transitions from the vertical coupling dimension of grating couplers to the lateral coupling dimension of edge couplers. This dimensional change enables wider spectral bandwidth operation while the accompanying lens and alignment features address the increased precision requirements through geometric design rather than material property optimization.

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

The solution achieves suppressed return loss and improved coupling efficiency between DFB-LD and Si PIC edge couplers, enhancing spectral bandwidth and compatibility with QSFP form factors, thereby addressing the link budget deficiency and enabling wider application in data centers.

Implementation Method 1

a lens disposed between the DFB-LD and the at least one input edge coupler of the Si PIC, and configured to minimize a mismatch between an output spot size of the DFB-LD and a spot size of the at least one input edge coupler

Methodology Applied

Scientific EffectOptical focusing: Lens

Implementation Method 2

an isolator bonded to a facet of the at least one input edge coupler with a first volume of an index matching fluid

Methodology Applied

Scientific EffectIndex matching: Refraction

Implementation Method 3

anti-reflection coating to reduce return loss

Methodology Applied

Scientific EffectAnti-reflection: Anti-Reflective Coating

Implementation Method 4

a single-mode fiber aligned to the at least one output edge coupler of the Si PIC

Methodology Applied

Scientific EffectOptical fiber transmission: Optical Fibre

Data Source

PatentUS9933585B2Low return loss silicon photonics package structure

Publication Date: 2018.04.03 SIFOTONICS TECH CO LTD

AI summary

A compact and highly efficient coupling structure for coupling between DFB-LD and Si PIC edge coupler with suppressed return loss may include a DFB-LD, a Si PIC comprising at least one input edge coupler and at least one output edge coupler, a silica cover lid disposed on the Si PIC and aligned edge to edge with the Si PIC, a single-mode fiber aligned to the at least one output edge coupler of the Si PIC, a lens disposed between the DFB-LD and the at least one input edge coupler of the Si PIC, and an isolator bonded to a facet of the at least one input edge coupler with a first volume of an index matching fluid. The lens may be configured to minimize a mismatch between an output spot size of the DFB-LD and a spot size of the at least one input edge coupler of the Si PIC.