Robust Subwavelength Mirror with Plasmonic Liner for HAMR

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Solution Overview

Problem

Heat-assisted magnetic recording (HAMR) devices face challenges due to wear and degradation of optical components, particularly subwavelength mirrors, which are subject to high temperatures and oxidation, leading to voiding and separation issues that affect the lifespan of recording heads.

Innovation Solution

The use of a mechanically robust subwavelength mirror with a reflective liner, where the core is made of materials resistant to mechanical wear and corrosion, and a plasmonic metal liner, such as Au or Al, is employed. This design includes a core with a first edge exposed at the media-facing surface and a liner covering the second edge, providing improved durability and optical performance by reducing thermal gradients and blocking background light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solid Au mirrors are used in HAMR devices, then optical performance is maintained, but mechanical wear and corrosion resistance deteriorate

Engineering Contradiction:

Improvedurability of subwavelength mirrorVSAvoidresistance to mechanical wear and corrosion

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies composite materials by combining a mechanically robust core material (such as Rh, Ir, Pt, Pd, Ru, or dielectric materials like SiO2, Al2O3, MgO, AlN) with a plasmonic metal liner (such as Au or Al). This composite structure provides both mechanical strength and wear resistance from the core, while the plasmonic liner maintains optical performance. The core material is selected based on specific requirements: Rh for oxidation resistance, Ir for mechanical strength, Pt for corrosion resistance, and dielectric materials for thermal management.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If plasmonic metal liners are used to maintain optical performance, then thermal gradient management deteriorates due to heat retention

Engineering Contradiction:

Improveoptical performance of subwavelength mirrorVSAvoidthermal gradient in HAMR device

Core Design Contradiction:

Illumination intensityVSTemperature

Solution Approach 1:

The patent applies local quality by making the subwavelength mirror partially transparent to light while maintaining its reflective properties for plasmonic enhancement. The core material is selected to be transparent or partially transparent to the laser wavelength used, allowing optical energy to pass through to the recording media while the plasmonic liner provides localized optical field enhancement. This selective transparency manages thermal gradients by allowing heat to dissipate while maintaining optical functionality.

Inventive Principle:

Principle #3Local quality

3Reliability

If the subwavelength mirror is made more robust mechanically, then manufacturing precision deteriorates due to stricter material requirements

Engineering Contradiction:

Improvelifespan of recording headVSAvoiddifficulty of fabricating robust core structure

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies segmentation by dividing the subwavelength mirror into two distinct functional components: a mechanically robust core structure and a thin plasmonic metal liner. The core structure provides mechanical strength and wear resistance, while the thin liner (5-50 nm) provides optical functionality. This segmentation allows each component to be optimized independently for its specific function, simplifying the overall manufacturing process while maintaining both mechanical robustness and optical performance.

Inventive Principle:

Principle #1Segmentation

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 enhances the durability and optical performance of HAMR devices by maintaining the effectiveness of the subwavelength mirror, reducing the required laser current, and improving thermal gradients, thus extending the lifespan of the recording heads while maintaining comparable performance to solid Au mirrors.

Implementation Method 1

A liner covers a second edge of the core facing the near-field transducer. The liner includes a plasmonic metal that is different than the core material, such as Au or Al.

Methodology Applied

Scientific EffectPlasmonic resonance:

Implementation Method 2

improving thermal gradients

Methodology Applied

Scientific EffectThermal gradient reduction:

Implementation Method 3

The near-field transducer extends a first distance away from the media-facing surface. A waveguide overlaps and delivers light to the near-field transducer.

Methodology Applied

Scientific EffectNear-field optical focusing:

Data Source

PatentUS11664051B1Heat-assisted recording head having mechanically robust subwavelength mirror with plasmonic liner

Publication Date: 2023.05.30 SEAGATE TECH LLC

AI summary

A recording head has a near-field transducer proximate a media-facing surface of the recording head. A waveguide overlaps and delivers light to the near-field transducer. Two subwavelength focusing mirrors are at an end of the waveguide proximate the media-facing surface. The subwavelength mirrors are on opposite crosstrack sides of the near-field transducer and separated from each other by a crosstrack gap. The subwavelength focusing mirrors each include a core having a first edge exposed at the media-facing surface. The core formed of a core material that is resistant to mechanical wear and corrosion, such as a dielectric or robust metal. A liner covers a second edge of the core facing the near-field transducer. The liner includes a plasmonic metal that is different than the core material, such as Au or Al.