Waveguide Core With Reduced Crosstrack Width For Near-Field Transducer

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Solution Overview

Problem

Existing waveguide designs for write heads suffer from stray light losses, which lead to unwanted modulation of the energy source and heating of the recording medium, due to inefficiencies in light coupling to the near-field transducer.

Innovation Solution

The waveguide core is tailored with regions of reduced cross-section and tapered near the near-field transducer to enhance energy redistribution and coupling efficiency, reducing stray light reflections and improving thermal gradients.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a conventional waveguide core with uniform cross-section is used, then light delivery to the near-field transducer is maintained, but stray light losses occur leading to unwanted modulation of the energy source and heating of the recording medium

Engineering Contradiction:

Improvestray light lossesVSAvoidwaveguide core structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The waveguide core implements local quality changes by introducing a reduced cross-section region (squeezed portion) at specific locations where light coupling to the near-field transducer occurs. This localized structural modification creates mode mismatch that reduces stray light feedback to the energy source while maintaining effective light delivery to the transducer, thereby reducing energy losses without requiring complete redesign of the entire waveguide structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The waveguide core is segmented into distinct regions: a first region with larger cross-section for light propagation from the energy source, and a second region with reduced cross-section (squeezed portion) for enhanced coupling to the near-field transducer. This segmentation allows different portions of the waveguide to perform optimized functions - the first region for efficient light transmission and the second region for reduced stray light feedback.

Inventive Principle:

Principle #1Segmentation

2Loss of energy

If the waveguide core is tailored with reduced cross-section regions, then stray light feedback is reduced by approximately 40%, but manufacturing precision requirements increase

Engineering Contradiction:

Improvestray light feedbackVSAvoidcore cross-section dimensions

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The invention applies parameter changes by modifying the cross-sectional dimensions of the waveguide core at specific locations. The squeezed portion has deliberately reduced cross-sectional area compared to the main waveguide core, creating a controlled mode mismatch. This parameter modification reduces the reflectivity and feedback of stray light to the energy source while maintaining sufficient light coupling to the near-field transducer, achieving approximately 40% reduction in stray light feedback.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If light coupling efficiency to the near-field transducer is improved, then media heating efficiency increases by about 5%, but stray light reflections increase causing unwanted modulation of the energy source

Engineering Contradiction:

Improvemedia heating efficiencyVSAvoidstray light reflections

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The invention converts the potentially harmful effect of light reflections into a beneficial outcome. By introducing the squeezed portion with reduced cross-section, the waveguide creates controlled mode mismatch that causes stray light to be scattered or absorbed rather than reflected back to the energy source. This transforms what would be harmful feedback into a mechanism that reduces unwanted modulations while maintaining effective heating of the recording medium.

Inventive Principle:

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

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 design reduces stray light feedback by approximately 40% and enhances media heating efficiency by about 5%, while maintaining effective light delivery to the recording medium.

Implementation Method 1

Waveguide of a write head with reduced crosstrack width proximate a near-field transducer

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

a near-field transducer near a media-facing surface of the write head... The light generates a surface plasmon field on the NFT, and the surface plasmons are directed out of a surface of the write head onto a magnetic recording medium. This creates a hotspot on the recording medium, lowering its magnetic coercivity

Methodology Applied

Scientific EffectNear-field optical heating: Absorption (EM radiation)

Data Source

PatentUS9524740B2Waveguide of a write head with reduced crosstrack width proximate a near-field transducer

Publication Date: 2016.12.20 SEAGATE TECH LLC

AI summary

A write head includes a near-field transducer near a media-facing surface of the write head and a waveguide. The waveguide includes a core that overlaps or is co-planer with the near-field transducer at a first region. The core has a second region extending away from the near-field transducer to an energy source. The core has a third region between the first and second regions. The third region has a third crosstrack width that is less than first and second crosstrack widths of the first and second regions.