Dielectric Waveguide NFT for EAMR Heat-Assisted Magnetic Recording

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Solution Overview

Problem

Inefficiencies in near field transducers (NFTs) used in Energy Assisted Magnetic Recording (EAMR) and Heat Assisted Magnetic Recording (HAMR) systems lead to high power demands and reduced mechanical robustness due to the susceptibility of plasmonic metals to thermal and mechanical stresses, limiting the service lifetime of these devices.

Innovation Solution

The use of dielectric waveguide cores with fine ridge features to interface with plasmonic metals, allowing for improved energy focusing and increased electrical field magnitude through surface plasmon polaritons, which enhances the efficiency and reliability of the NFT, reducing the need for high laser power and increasing the device's service life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If plasmonic metal is used to interface with dielectric waveguide for propagating surface plasmon polaritons, then optical energy focusing capability is improved, but mechanical robustness deteriorates due to susceptibility to thermal and mechanical stresses

Engineering Contradiction:

Improveoptical energy focusing capabilityVSAvoidmechanical robustness

Core Design Contradiction:

Illumination intensityVSStrength

Solution Approach 1:

The patent employs a composite structure combining dielectric waveguide material (such as alumina, silica, or silicon oxide) with metallic layers (such as aluminum, silver, or gold). The dielectric waveguide core provides mechanical strength and structural stability, while the metallic layers enable surface plasmon polariton propagation for optical energy focusing. This composite approach allows the NFT to achieve both high optical efficiency and improved mechanical robustness under thermal and mechanical stresses in EAMR/HAMR systems.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If higher NFT efficiency is achieved, then laser power demand is reduced, but device complexity increases due to fine ridge feature fabrication

Engineering Contradiction:

Improvelaser power demandVSAvoidfine ridge feature fabrication

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent utilizes precise control of waveguide core dimensions (width, height, and ridge feature geometry) to optimize surface plasmon polariton coupling efficiency. By adjusting parameters such as waveguide core width (50-200 nm), height (20-100 nm), and ridge feature dimensions, the system achieves enhanced optical energy focusing and improved NFT efficiency, thereby reducing laser power demand while maintaining manufacturability through standard nanofabrication techniques.

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If plasmonic metal with fine features is used, then nano-focusing function is improved, but service lifetime is limited due to failure at fine feature locations under stress

Engineering Contradiction:

Improvenano-focusing functionVSAvoidservice lifetime

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The dielectric waveguide core acts as an intermediary structure that supports and protects the metallic layers containing fine ridge features. The dielectric material provides mechanical strength and structural stability, shielding the fragile metallic fine features from direct exposure to thermal and mechanical stresses. This intermediary structure enables the NFT to maintain nano-focusing functionality while significantly improving service lifetime by preventing failure at the fine feature locations.

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 results in lower power requirements for the laser diode, reduced parasitic heating, and improved mechanical robustness, leading to increased reliability and extended service life of EAMR/HAMR devices by optimizing energy delivery and focusing capabilities.

Implementation Method 1

plasmonic metal can be used to interface with an energized dielectric waveguide for propagating surface plasmon polaritons (SPPs), which carry out the nano-focusing function beyond the light's diffraction limit

Methodology Applied

Scientific EffectSurface plasmon polaritons:

Implementation Method 2

The NFT focuses the optical energy to a small spot on the target recording area which heats the magnetic storage disk during a write operation

Methodology Applied

Scientific EffectOptical heating:

Data Source

PatentUS9159346B1Near field transducer using dielectric waveguide core with fine ridge feature

Publication Date: 2015.10.13 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

An apparatus for energy assisted magnetic recording of a storage disk includes a plurality of dielectric waveguide cores disposed near an air bearing surface of a magnetic recording device. Each waveguide core has a fine ridge feature on a first surface of the waveguide core and configured to receive incident light energy from an energy source. A near field transducer (NFT) is formed at the air bearing surface for focusing light energy received from the waveguide core and transmitting the focused light energy onto the storage disk surface to generate a heating spot. The NFT includes at least one plasmonic metal element disposed above the fine ridge features of the waveguide cores to form an interface for delivering propagating surface plasmon polaritons (PSPPs) to the air bearing surface. Each fine ridge feature is configured with a width approximately equivalent to a width of the heating spot.