Near-field light generating element with waveguide and plasmon antenna
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Solution Overview
Problem
Current thermally-assisted magnetic recording techniques face challenges in achieving high light use efficiency due to propagation loss of excited surface plasmons in near-field light generating elements, which affects the ability to properly read servo signals and write data effectively.
Innovation Solution
A near-field light generating element is designed with a waveguide and a plasmon antenna where the side surface of the waveguide extends near the near-field light generating end, and the propagation surface or edge of the plasmon antenna is positioned with a specific distance to minimize propagation loss, allowing surface plasmons to propagate without significant wavenumber change, thereby improving light use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser light is directly applied to a plasmon antenna, then near-field light can be generated, but the temperature of the plasmon antenna excessively rises causing thermal expansion and degradation of light use efficiency
Solution Approach 1:
The patent introduces a waveguide as an intermediary component between the laser light source and the plasmon antenna. The waveguide transmits laser light to the plasmon antenna without direct exposure, allowing controlled coupling of light to the antenna structure. This intermediary arrangement enables near-field light generation while preventing excessive temperature rise in the plasmon antenna, as the waveguide manages the energy transfer process efficiently.
2Illumination intensity
If the tip of a plasmon antenna is made closer to a magnetic recording medium, then stronger near-field light can be irradiated, but propagation loss increases reducing light use efficiency
Solution Approach 1:
The patent optimizes the geometric parameters of the plasmon antenna, specifically the width and shape of the propagation edge. By carefully controlling these dimensions, the antenna achieves efficient surface plasmon propagation with minimal loss. The optimized geometry allows the antenna to maintain high light use efficiency even when positioned close to the magnetic recording medium, resolving the contradiction between proximity for strong irradiation and distance for low propagation loss.
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 light use efficiency to 10% or more, necessary for favorable thermally-assisted magnetic recording, by reducing propagation loss and maintaining efficient heating of the write position on the magnetic recording medium.
Implementation Method 1
laser light propagating through a waveguide is coupled with a plasmon antenna in a surface plasmon mode to cause the excited surface plasmon to propagate to the opposed-to-medium surface
Implementation Method 2
a near-field light probe formed of a metal piece, so-called a plasmon antenna, is used for generating near-field light from plasmon that is excited by irradiated laser light
Implementation Method 3
the magnetic recording medium is irradiated with near-field light, thereby anisotropic magnetic field of the medium is lowered, thus data can be written
Data Source
AI summary
Provided is a near-field light generating element in which reduced is the propagation loss of excited surface plasmon that propagates to the near-field light generating end. The element comprises: a waveguide through which light for exciting surface plasmon propagates; and a plasmon antenna comprising a near-field light generating end and a propagation surface or edge. The propagation surface or edge extends to the near-field light generating end, and causes surface plasmon excited by the light to propagate thereon. Further, a portion of the side surface on the near-field light generating end side is opposed to the propagation surface or edge with a predetermined distance so as for the light to be coupled with the plasmon antenna in a surface plasmon mode. In this configuration, surface plasmon can propagates without significantly changing its wavenumber, which leads to a less propagation loss, and to an improved light use efficiency.