Waveguide Attenuating Higher Order TM Mode Light
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Solution Overview
Problem
Conventional magnetic recording technologies face challenges in increasing recording density due to the trade-off between magnetic micro particle size, thermal stability, and coercive force, where reducing particle size decreases thermal stability and increases coercive force, making it difficult to record information effectively.
Innovation Solution
A waveguide system that attenuates higher order TM modes by using a core with a rectangular cross section and a surrounding cladding with a light absorbing element positioned away from the core, allowing only fundamental mode light to pass through while absorbing higher order mode light, thereby improving energy efficiency and preventing excessive temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If magnetic micro particles are decreased in size to enhance recording density, then recording density is improved, but thermal stability of magnetization is reduced
Solution Approach 1:
The patent changes the physical state and parameters of the magnetic recording medium by heating it to a temperature where the coercive force decreases, allowing easier magnetic particle orientation. This temperature parameter change enables recording at higher densities while maintaining stability through controlled thermal conditions.
Solution Approach 2:
The patent utilizes a phase transition in the phase change layer, switching between crystalline and amorphous states. The crystalline state provides high reflectivity for signal detection, while the amorphous state allows for magnetic recording. This phase transition enables the system to achieve both high recording density and thermal stability.
2Stability of the object's composition
If anisotropic energy of magnetic micro particles is increased to improve thermal stability, then thermal stability is improved, but coercive force becomes great making recording difficult
Solution Approach 1:
The patent changes the temperature parameter of the magnetic recording medium to a state where coercive force is reduced, enabling magnetic particle orientation even when anisotropic energy is high. This parameter change allows the system to overcome the high coercive force barrier while maintaining thermal stability through controlled heating.
Solution Approach 2:
The patent employs phase transition in the phase change layer to modulate the magnetic properties of the underlying magnetic layer. During phase transition, the magnetic anisotropy is reduced, allowing easier magnetization switching despite high anisotropic energy in the magnetic particles, thus enabling recording with maintained thermal stability.
3Illumination intensity
If light is directly irradiated to plasmon antenna to generate near field light, then near field light generation is achieved, but conversion efficiency is low and excessive temperature rise occurs
Solution Approach 1:
The patent introduces a waveguide as an intermediary component between the light source and the plasmon antenna. The waveguide efficiently guides and directs light to the plasmon antenna with minimal loss, improving conversion efficiency. The waveguide structure with specific refractive index matching reduces reflection and scattering losses, enabling more effective near field light generation.
4Volume of moving object
If plasmon antenna volume is reduced to achieve smaller focus size, then light focusing capability is improved, but temperature rise becomes very great causing expansion and protrusion
Solution Approach 1:
The patent uses a waveguide as an intermediary to deliver light energy more efficiently to the plasmon antenna, reducing the need for excessive energy concentration in a tiny volume. This intermediary structure allows for better heat management while maintaining the small focus size capability, preventing thermal expansion and protrusion issues.
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 solution enhances the recording density by maintaining thermal stability while reducing coercive force, allowing for efficient generation of surface plasmons and improved read/write capabilities in thermally-assisted magnetic recording systems.
Implementation Method 1
a light absorbing element in the clad, the light absorbing element being positioned away from a surface of the core perpendicular to the cross section and perpendicular to the direction in which two or more portions exist where the light intensity becomes maximal
Implementation Method 2
a core through which laser light can propagate in a TM mode, that has a rectangular cross section perpendicular to a propagative direction of the laser light
Implementation Method 3
the surface plasmon is excited in the plasmon generator. The excited surface plasmon propagates to an edge of near-field-generator along the plasmon generator, and generates the near field light at the edge of near-field-generator
Implementation Method 4
Near field light is a type of so-called electromagnetic field to be formed around a substance. Normal light cannot be tapered (narrowed) to a region that is smaller than the wavelength of the light due to a diffraction limitation. However, irradiation of lights with the same wavelength causes the generation of near field light depending upon the microstructure scale, and enables light to be sharply focused on the order of tens of nm on a minimal region.
Data Source
AI summary
A waveguide has a core through which laser light can propagate in a TM mode, that has a rectangular cross section perpendicular to a propagative direction of the laser light, and through which the laser light can propagate in a fundamental mode in which only one portion exists on the cross section of the core where a light intensity of the laser light becomes maximal, and a higher order mode in which two or more portions exist where the light intensity becomes maximal, a clad surrounding the core, and a light absorbing element in the clad, and wherein a distance between the light absorbing element and the core is shorter than a penetration length of evanescent light in the higher order mode, but is longer than a penetration length of evanescent light in the fundamental mode.