Waveguide Power Absorption Measurement Using Non-Periodic NFT Spacing

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Solution Overview

Problem

Energy-assisted magnetic recording systems face challenges in accurately measuring the energy transfer efficiency from a waveguide to near-field transducers (NFTs) due to energy losses throughout the system, making it difficult to precisely determine the amount of energy absorbed by NFTs, especially when using single NFTs or those with small absorption differences.

Innovation Solution

Employing multiple test structures with varying numbers of NFTs and optimizing their spacing to improve measurement accuracy, allowing for more precise absorption measurements by comparing output light powers between structures with different NFT configurations, and using non-periodic spacing to minimize interference and enhance measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple NFTs are used to improve measurement accuracy, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improveabsorption measurement accuracyVSAvoidtest structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The test structure is segmented into multiple identical or different NFT elements arranged in series on the waveguide. By dividing the measurement function across multiple NFTs, the system achieves better measurement sensitivity and accuracy while maintaining a modular structure that simplifies analysis and interpretation of results.

Inventive Principle:

Principle #1Segmentation

2Area of stationary object

If NFTs are placed closer together to reduce device size, then area is reduced, but wave interference increases reducing measurement accuracy

Engineering Contradiction:

Improvewaveguide areaVSAvoidabsorption measurement accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The spacing between NFTs is optimized based on local measurement requirements. Different regions of the waveguide may have different NFT spacing arrangements, with critical measurement zones having optimized spacing to minimize interference while maintaining compact overall device footprint.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The spacing parameter between NFTs is carefully adjusted and optimized. By changing the spatial arrangement parameter (spacing distance), the system achieves a balance between compact device size and measurement accuracy, avoiding harmful wave interference while maintaining small form factor.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If periodic spacing is used to simplify design, then device complexity is reduced, but wave interference increases reducing measurement accuracy

Engineering Contradiction:

Improvespacing arrangement complexityVSAvoidabsorption measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Instead of uniform periodic spacing, the NFTs are arranged with asymmetric or non-uniform spacing patterns. This asymmetric arrangement disrupts the formation of coherent wave interference patterns while maintaining a relatively simple design framework, thereby improving measurement accuracy without significantly increasing design complexity.

Inventive Principle:

Principle #4Asymmetry

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 approach significantly improves the ability to measure energy absorption by NFTs, reducing uncertainty and enhancing the precision of performance evaluation, particularly by using non-periodic spacing which reduces wave interference and improves data accuracy.

Implementation Method 1

a planar waveguide which serves as light delivery path

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

NFT's are typically mounted on a waveguide to take advantage the surface plasmon waves to create local electro-magnetic fields

Methodology Applied

Scientific EffectSurface plasmon resonance:

Data Source

PatentUS8749790B1Structure and method to measure waveguide power absorption by surface plasmon element

Publication Date: 2014.06.10 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A structure for measuring energy absorption by a surface plasmon receptor or NFT on a waveguide comprises a first waveguide, a first input grating for coupling light comprising a first wavelength into the first waveguide, a first output grating for coupling light out of the first waveguide, a first plurality of surface plasmon receptors in cooperation with the first waveguide to receive light energy and located between the first input grating and the first output grating. The structure may further comprise a second waveguide, a second input grating for coupling light into the second waveguide, a second output grating for coupling light out of the second waveguide, a second plurality of surface plasmon receptors between the second input grating and the second output grating and in cooperation with the second waveguide to receive light energy, wherein the second plurality may be less than or greater than the first plurality.