Gradient-index lens with tilted sidewalls for laser coupling

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Solution Overview

Problem

The precise alignment of laser diodes with read/write heads in nanophotonic platforms is challenging, especially when using wafer-bonded lasers, leading to inefficiencies in light coupling and potential misalignment issues that can render heads unusable.

Innovation Solution

A gradient-index lens with tilted sidewalls is used to couple light from a laser active region to a waveguide core, formed by alternating layers of different refractive indices that conform to a planar base and tilted sidewalls, enabling efficient light coupling and tolerance to misalignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If wafer-bonded lasers are used to integrate laser diodes with read/write heads, then device integration is improved, but alignment precision deteriorates

Engineering Contradiction:

Improvedevice integrationVSAvoidalignment precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The gradient-index lens acts as an intermediary optical element between the laser diode and waveguide core. It receives light from the laser active region and directs it into the waveguide core, accommodating misalignment through its gradient-index structure that guides light rays toward the waveguide core regardless of small positional deviations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a gradient-index structure where the refractive index varies continuously from the center to the periphery of the lens. This parameter change in refractive index creates light-bending effects that tolerate misalignment while maintaining efficient coupling, resolving the contradiction between integration and precision.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If conventional light coupling methods are used, then device simplicity is maintained, but coupling efficiency deteriorates

Engineering Contradiction:

Improvedevice simplicityVSAvoidcoupling efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The gradient-index lens uses a continuous variation of refractive index from center to periphery, creating optimal light path bending that maximizes coupling efficiency. The tilted sidewalls further optimize light direction into the waveguide core, achieving nearly 80% coupling efficiency while maintaining relatively simple device architecture.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The gradient-index lens employs curved light paths through its radially varying refractive index profile, replacing straight-line optical paths with optimized curved trajectories that efficiently direct light from the laser diode into the waveguide core, significantly improving coupling efficiency.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Reliability

If misalignment tolerance is increased, then system reliability is improved, but optical performance deteriorates

Engineering Contradiction:

Improvemisalignment toleranceVSAvoidoptical performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The gradient-index profile is specifically designed with a particular refractive index distribution that simultaneously provides misalignment tolerance and maintains high optical performance. The continuous refractive index variation guides off-axis light rays back toward the optical axis, ensuring both reliability against misalignment and high coupling efficiency.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The lens is constructed with composite bilayer structure having different refractive indices in alternating layers, creating an effective gradient-index profile. This composite structure enables both misalignment tolerance through light-bending and high optical performance through optimized effective refractive index distribution.

Inventive Principle:

Principle #40Composite materials

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 gradient-index lens achieves high coupling efficiency (nearly 80%) and improves tolerance to misalignment, reducing losses and enhancing the performance of the light delivery system.

Implementation Method 1

The gradient-index lens includes a plurality of bilayers, each of the bilayers having first and second material of respective first and second refractive indices

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS9875761B1Gradient-index lens with tilted sidewall

Publication Date: 2018.01.23 SEAGATE TECH LLC

AI summary

A gradient-index lens couples light from a laser active region to a waveguide core. The gradient-index lens includes a plurality of bilayers, each of the bilayers having first and second material of respective first and second refractive indices. The bilayers conform to a planar base of the gradient-index lens and further conform to input and output sidewalls of the gradient-index lens. The input sidewall faces the laser active region and the output sidewall faces away from the laser active region. The input and output sidewalls are tilted at respective acute angles relative to the planar base.