GRIN Lens Coupling for Photonic Integrated Circuits

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Solution Overview

Problem

The coupling of photonic integrated circuits (PICs) to optical fibers requires precise alignment, which is challenging due to high signal loss and high equipment costs, limiting high-volume manufacturing, and existing solutions like V-groove architectures and self-aligned mirrors are complex and costly to fabricate.

Innovation Solution

The use of graded index (GRIN) lenses with a planar surface design for improved coupling efficiency, which can be formed through diffusion or additive manufacturing processes, simplifying the assembly and reducing fabrication complexity by avoiding lateral offset and angular misalignments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If precise alignment with tight tolerances is used for PIC coupling, then coupling efficiency is improved, but manufacturing cost and equipment cost increase significantly

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidalignment precision requirement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A GRIN lens is introduced as an intermediary optical component between the PIC and optical fiber. The lens performs mode field transformation and beam shaping functions, enabling efficient coupling without requiring sub-micron alignment precision. This mediator component relaxes the tight tolerance requirements while maintaining high coupling efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent utilizes gradient index (variable refractive index) parameter change within the lens material to achieve focusing and beam shaping without curved surfaces. This parameter change enables the lens to correct optical aberrations and improve coupling efficiency while maintaining planar geometry that simplifies alignment requirements.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If V-groove architectures or self-aligned mirrors are used to improve alignment, then coupling precision is improved, but fabrication complexity and processing steps increase

Engineering Contradiction:

Improvealignment precisionVSAvoidfabrication complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The optical coupling function is segmented into two independent parts: the GRIN lens handles optical beam transformation while the mechanical mounting structure handles positioning. This segmentation allows each component to be optimized independently, simplifying fabrication compared to integrated V-groove or mirror structures that require multiple precise processing steps.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of creating complex curved surfaces or V-grooves to achieve alignment, the patent inverts the approach by using planar surfaces with a GRIN lens that achieves optical focusing through refractive index gradient rather than geometric curvature. This inversion simplifies manufacturing while maintaining optical performance.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If inserted or fabricated couplers are used to improve coupling efficiency, then optical coupling is improved, but insertion loss increases due to surface roughness

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent replaces mechanical surface contact coupling (which suffers from roughness-related losses) with optical field-based coupling through the GRIN lens. The lens focuses and shapes optical beams through refractive index gradients, eliminating the need for high-precision mechanical surface contact and reducing insertion loss from surface roughness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 GRIN lenses enhance optical coupling efficiency by focusing and collimating optical signals without curved surfaces, reducing signal loss and fabrication costs, and enabling easier integration into PIC packages, thus improving manufacturing yield and reducing the complexity of the assembly process.

Implementation Method 1

a lens optically coupled to the optical fiber, wherein the lens is a gradient index (GRIN) lens

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

the placement accuracy tolerance is on the micron scale with an angle tolerance less than two degrees... GRIN lenses enhance optical coupling efficiency by focusing and collimating optical signals

Methodology Applied

Scientific EffectTotal Internal Reflection: Total Internal Reflection

Data Source

PatentUS20240210634A1Functionally graded index mold for co-packaged optical applications

Publication Date: 2024.06.27 INTEL CORP

AI summary

Embodiments disclosed herein include a package substrate. In an embodiment, the package substrate comprises a substrate and an optical fiber in the substrate. In an embodiment, a lens is optically coupled to the optical fiber. In an embodiment, the lens is a gradient index (GRIN) lens.