Subwavelength Mirror Liner Reduces Evanescent Coupling in HAMR Heads

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In heat-assisted magnetic recording (HAMR) devices, evanescent coupling between subwavelength mirrors and near-field transducers reduces efficiency due to the use of noble metals like Au, which affects the performance of the near-field transducer.

Innovation Solution

The implementation of a subwavelength mirror design with a plasmonic metal liner, such as Al, Mg, or In, separated by a gap of less than 50 nm from the near-field transducer, reduces evanescent coupling by using materials with high extinction coefficients and plasmonic frequencies in the ultraviolet range, improving thermal gradients and optical performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If noble metals like Au are used for subwavelength mirrors, then mechanical wear resistance and corrosion resistance are improved, but evanescent coupling with near-field transducer increases reducing efficiency

Engineering Contradiction:

Improvemechanical wear resistance and corrosion resistanceVSAvoidevanescent coupling loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The mirror structure is segmented into two distinct parts: a core made of noble metal (Au, Ag, or Cu) for mechanical durability, and a liner made of UV-plasmonic material (Al, Mg, or In) for optical performance. This segmentation allows each material to fulfill its optimal function without the drawbacks of using a single material for both purposes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining noble metal core with UV-plasmonic material liner. The core provides mechanical strength and corrosion resistance, while the liner provides high extinction coefficient and UV plasmonic frequency to reduce evanescent coupling. This composite approach resolves the contradiction between mechanical reliability and energy loss.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If gap between subwavelength mirror and near-field transducer is reduced, then optical focusing is improved, but evanescent coupling increases reducing transducer efficiency

Engineering Contradiction:

Improveoptical focusing intensityVSAvoidevanescent coupling loss

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The liner material properties are specifically optimized for the local region where it interfaces with the near-field transducer. The UV-plasmonic material's high extinction coefficient and UV-range plasmonic frequency create a localized optical field that focuses light effectively while minimizing evanescent coupling to the transducer, even at sub-50nm gaps.

Inventive Principle:

Principle #3Local quality

3Temperature

If plasmonic metal liner with high extinction coefficient is used, then thermal gradient is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvethermal gradientVSAvoidmanufacturing complexity

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The UV-plasmonic material liner acts as an intermediary layer between the noble metal core and the near-field transducer. This intermediary provides the necessary optical properties (high extinction coefficient, UV plasmonic frequency) to achieve superior thermal gradient and optical performance, while the noble metal core provides structural support that simplifies overall manufacturing.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration enhances the thermal gradient and reduces optical writing power, leading to improved areal density capability and reduced peg temperature, thereby increasing the efficiency of the near-field transducer.

Implementation Method 1

The liner includes a plasmonic metal that is different than the core material and that has at least one of: a plasmonic frequency in an ultraviolet range; and an extinction coefficient greater than 6

Methodology Applied

Scientific EffectExtinction coefficient: Absorption (EM radiation)

Implementation Method 2

The liner includes a plasmonic metal that is different than the core material and that has at least one of: a plasmonic frequency in an ultraviolet range; and an extinction coefficient greater than 6

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Data Source

PatentUS11823719B1Heat-assisted recording head having mirror liner that reduces evanescent coupling with near field transducer

Publication Date: 2023.11.21 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, the light having a near-infrared wavelength. 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 a peg of the near-field transducer by a 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 has a plasmonic frequency in the ultraviolet range.