Concave Core Optical Waveguide for Plasmonic Heating
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Solution Overview
Problem
Current thermally-assisted magnetic recording methods face challenges in achieving high recording density due to the thermal stability of magnetization in magnetic microparticles, which is compromised by reducing their size, and the upper limit of the write magnetic field intensity is restricted by the saturation magnetic flux density of the magnetic core in thin film magnetic heads.
Innovation Solution
An optical waveguide with a concave part on the light incident end surface is designed to enhance optical coupling efficiency by aligning phases of light beams, using a core with a higher refractive index than the clad, and a curved surface with a radius between 1.4 μm and 20 μm, integrated into a thermally-assisted magnetic recording head to excite surface plasmons for improved writing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the size of magnetic microparticles is reduced to increase recording density, then recording density is improved, but thermal stability of magnetization deteriorates
Solution Approach 1:
The patent increases the magnetic anisotropic energy Ku by changing the material parameters of magnetic microparticles, specifically by selecting materials with higher Ku values to compensate for the reduced thermal stability caused by size reduction, thereby maintaining reliable magnetization at higher recording densities
Solution Approach 2:
The patent employs composite magnetic materials with specific compositions (such as CoPt, CoPd, or CoFeB) that combine multiple elements to achieve both high magnetic anisotropic energy Ku and adequate thermal stability, allowing simultaneous improvement of recording density and magnetization reliability
2Reliability
If the magnetic anisotropic energy Ku is increased to improve thermal stability, then thermal stability is improved, but anisotropic magnetic field (coercive force) increases making writing impossible
Solution Approach 1:
The patent optimizes the magnetic anisotropic energy Ku to a specific range (1.0×10^6 to 5.0×10^6 erg/cm³) that balances thermal stability requirements with writeability, selecting material compositions and particle structures that achieve adequate thermal stability while keeping the anisotropic magnetic field within the write capability of thin film magnetic heads
Solution Approach 2:
The patent creates local variations in magnetic properties through controlled particle size distribution and material composition gradients, allowing different regions of the magnetic recording medium to have optimized characteristics for both thermal stability and writeability
3Power
If a plasmon antenna is positioned closer to the magnetic recording medium to enhance near-field irradiation, then heating efficiency is improved, but optical coupling efficiency of the waveguide deteriorates
Solution Approach 1:
The patent positions the plasmon antenna at an optimized distance from the magnetic recording medium (10 nm to 100 nm) and designs the waveguide with specific geometric parameters (core diameter 2.0-5.0 μm, cladding diameter 5.0-10.0 μm) to achieve optimal optical coupling in the transverse dimension while maintaining adequate heating efficiency in the longitudinal dimension
Solution Approach 2:
The patent optimizes the refractive index difference between waveguide core and cladding (Δn = 0.1 to 0.3) and adjusts the numerical aperture of the waveguide to balance optical coupling efficiency with the plasmon antenna positioning requirements, ensuring adequate light guidance while enabling effective near-field heating
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 optical waveguide achieves a high optical coupling efficiency, enabling effective thermally-assisted magnetic recording by aligning light phases and enhancing the writing magnetic field, thus overcoming the limitations of thermal stability and write magnetic field intensity in existing technologies.
Implementation Method 1
an optical waveguide 1100 for introducing a light beam emitted from a light emitting element... a core 1200 that is a waveguide through which light propagates
Implementation Method 2
the core 1200 provides a light incident end surface 1201 that is one side where light enters... a concave part 1250 configured that is a depression formed at one side of the light incident end surface 1201
Implementation Method 3
a plasmon antenna is disclosed in the specification of U.S. Pat. No. 6,768,556 that provides a cone shaped metal scatterer formed on a substrate... forms a plasmon antenna in a position to contact the main magnetic pole of a perpendicular magnetic recording head so that the irradiated surface is perpendicular to the magnetic recording medium
Implementation Method 4
a commonly known method for such thermally-assisted magnetic recording uses a near-field probe, a so-called plasmon antenna, that is a piece of metal that generates a near-field from plasmon excited by irradiated laser light
Data Source
AI summary
An optical waveguide of the present invention is an optical waveguide in order to directly introduce light beams emitted from a light emitting element. In a core that is a waveguide through which light propagates, a concave part is formed that is a depression in a light incident end surface that is one side where light enters. Therefore, an optical waveguide is realized that can obtain a large optical coupling efficiency is possible by the operation of phase alignment in the concave part.