Near-field light generating element for HAMR heads
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Solution Overview
Problem
Conventional heat-assisted magnetic recording heads face inefficiencies in generating near-field light due to poor laser light use efficiency and thermal management issues with plasmon antennas, leading to difficulties in exciting surface plasmons and maintaining thermal stability.
Innovation Solution
A near-field light generating element with a tip at the front end face is designed to concentrate surface plasmons, utilizing a waveguide to excite evanescent light and propagate it to the tip, enhancing surface plasmon excitation and concentration, while maintaining a larger volume to prevent thermal expansion and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional plasmon antenna is used to generate near-field light, then the structure is simple, but the laser light use efficiency is poor due to reflection and thermal energy conversion
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the laser light source and the plasmon antenna. This dielectric layer acts as a mediator to improve the coupling efficiency between the laser light and the plasmon antenna, reducing light reflection and enhancing the conversion of laser light into surface plasmons, thereby improving overall laser light use efficiency
Solution Approach 2:
The refractive index of the dielectric layer is specifically designed to be between 1.3 and 2.0, which is a critical parameter change. This refractive index range optimizes the light-plasmon coupling by creating appropriate optical impedance matching, reducing reflection losses and enhancing the efficiency of near-field light generation
2Power
If the plasmon antenna absorbs thermal energy from laser light, then near-field light generation occurs, but the antenna temperature increases causing expansion and protrusion that damages the recording medium
Solution Approach 1:
The dielectric layer serves as a thermal management intermediary by providing thermal pathways that distribute the absorbed thermal energy away from the plasmon antenna. This prevents localized temperature rise and subsequent thermal expansion of the antenna, eliminating the damage risk to the recording medium while preserving near-field light generation capability
Solution Approach 2:
The thermal energy that would otherwise cause harmful expansion is converted into a beneficial effect by utilizing it to maintain the plasmon antenna at an optimal operating temperature. The dielectric layer's thermal properties are engineered to dissipate excess heat while maintaining sufficient thermal energy for efficient plasmon excitation, transforming the harmful thermal effect into a useful operational parameter
3Volume of moving object
If the plasmon antenna is made small to achieve near-field light, then the light confinement is improved, but the volume is reduced leading to excessive temperature increase upon thermal energy absorption
Solution Approach 1:
The system is segmented into distinct functional components: the plasmon antenna for light generation, the dielectric layer for thermal management, and the underlying substrate for structural support. This segmentation allows the antenna to maintain its small volume for near-field confinement while the dielectric layer handles thermal dissipation, preventing excessive temperature rise despite the antenna's limited volume
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 allows for efficient generation and concentration of near-field light with a small spot diameter and sufficient intensity, improving data writing capabilities and thermal stability in heat-assisted magnetic recording.
Implementation Method 1
Light propagated through the wave guide is totally reflected by the outer surface of the waveguide to generate evanescent light
Implementation Method 2
evanescent light is utilized to excite surface plasmons on the near-field light generating element
Implementation Method 3
The surface plasmon is propagated to the near-field light generating part, and the near-field light generating part generates near-field light based on the surface plasmon
Implementation Method 4
the laser light can be reflected at the surface of the plasmon antenna or can be converted into thermal energy and absorbed by the plasmon antenna
Implementation Method 5
a write head including an induction-type electromagnetic transducer for writing
Data Source
AI summary
A near-field light generating element has an outer surface including a bottom surface that lies at an end closer to a top surface of a substrate, a waveguide facing surface that lies at an end farther from the top surface of the substrate and faces a waveguide, a front end face located in a medium facing surface, and a side surface that connects the bottom surface, the waveguide facing surface and the front end face to each other. The front end face includes a first side that lies at an end of the bottom surface, a tip that lies at an end farther from the top surface of the substrate and forms a near-field light generating part, a second side that connects an end of the first side to the tip, and a third side that connects the other end of the first side to the tip. The waveguide facing surface includes a width changing portion that has a width in a direction parallel to the bottom surface and the front end face, the width decreasing with decreasing distance to the front end face.