TAR Head Reflection Layer Phase Matching for Near-Field Intensity
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Solution Overview
Problem
Conventional thermally-assisted recording (TAR) systems require high laser power to achieve efficient data recording due to inefficiencies in the near-field transducer (NFT) design, which can lead to thermal instabilities and data loss.
Innovation Solution
The TAR head incorporates an air-bearing slider with a near-field transducer (NFT) and an optical waveguide, where the reflection layer's distance from the NFT is optimized to match the phase of plasma oscillations, increasing the intensity of the optical near-field and reducing the required laser power. This is achieved by adjusting the distance between the reflection layer and the center of the NFT to be between 0.8N*λ/(2n) and 1.2N*λ/(2n), where N is an integer, λ is the laser wavelength, and n is the average refractive index of the waveguide and insulating material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional NFT design is used, then thermal stability is maintained, but laser power requirement increases and recording efficiency decreases
Solution Approach 1:
The patent implements an optical feedback mechanism where scattered light from the NFT is reflected back by a reflection layer to the NFT apex. This feedback loop enhances the optical near-field intensity and improves energy efficiency. The feedback path is configured with specific geometric parameters (apex angle, distance ratios) to optimize the reinforcement effect while maintaining system stability.
Solution Approach 2:
The patent introduces a three-dimensional geometric configuration involving the reflection layer positioned at a specific distance and angle relative to the NFT. By optimizing the apex angle (15-45 degrees) and the distance ratio (0.3-0.7) between the reflection layer and NFT, the system exploits spatial dimensionality to enhance optical field concentration and reduce laser power requirements.
2Productivity
If laser power is increased to improve recording efficiency, then near-field intensity increases, but thermal instabilities and data loss increase
Solution Approach 1:
The optical feedback mechanism concentrates and recycles scattered light back to the NFT apex, creating a localized intensity enhancement without requiring increased overall laser power. This feedback-driven concentration allows efficient recording while avoiding the thermal instabilities associated with high-power laser illumination.
Solution Approach 2:
The patent creates a highly localized optical near-field at the NFT apex through precise geometric configuration of the reflection layer and apex angle. This local field enhancement concentrates the optical energy exactly where needed (at the recording spot) while keeping the overall laser power low, thereby avoiding thermal instabilities in surrounding areas.
3Power
If reflection layer distance is not optimized, then device complexity is reduced, but optical near-field intensity decreases and laser power requirement increases
Solution Approach 1:
The patent optimizes specific geometric parameters of the NFT structure, including the apex angle (15-45 degrees) and the distance ratio between the reflection layer and NFT (0.3-0.7). By carefully controlling these parameters, the system achieves enhanced optical feedback efficiency and reduced laser power requirements without introducing excessive structural complexity.
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 reduces the necessary laser power while maintaining or enhancing the optical near-field intensity, thereby improving the efficiency of the TAR head and stabilizing recorded data.
Implementation Method 1
an optical waveguide that directs laser light to the NFT
Implementation Method 2
The scattered light propagated by the waveguide is reflected back by the reflection layer to the NFT
Implementation Method 3
When the distance between the reflection layer and the center of the NFT in the along-the-track direction is adjusted so the phase of the reflected light matches the phase of the plasma oscillation in the NFT, the intensity of the optical near-field is increased
Implementation Method 4
an evanescent wave generated at a surface of the waveguide couples to surface plasmons excited on the surface of the NFT and a strong optical near-field is generated at the apex of the triangular output end
Implementation Method 5
the magnetic recording material is heated locally during writing to lower the coercivity enough for writing to occur
Implementation Method 6
thermally-assisted recording (TAR), also called heat-assisted magnetic recording (HAMR), wherein high-Ku magnetic recording material is heated locally during writing
Data Source
AI summary
A thermally-assisted recording (TAR) head for recording data in data tracks of a TAR disk is supported on an air-bearing slider and includes a near-field transducer (NFT) and an optical waveguide that directs laser light to the NFT. The NFT has an output end at the slider's air-bearing surface (ABS) located between the write pole and the optical waveguide in the along-the-track direction. A reflection layer is located on the side of the waveguide opposite the NFT. The scattered light propagated by the waveguide is reflected back by the reflection layer to the NFT. When the distance between the reflection layer and the center of the NFT in the along-the-track direction is adjusted so the phase of the reflected light matches the phase of the plasma oscillation in the NFT, the intensity of the optical near-field is increased. This allows for a reduction in laser power.