Electromagnetic Shield for Near-Field Transducer Thermal Sensor
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Solution Overview
Problem
In heat-assisted magnetic recording (HAMR) disk drives, the temperature monitoring of near-field transducers (NFTs) is compromised by optical coupling, leading to inaccurate readings and reduced reliability due to background electromagnetic radiation, necessitating improved methods for accurate temperature detection.
Innovation Solution
A write head design incorporating a magnetic or conductive shield between the NFT and thermal sensor, made from materials like Cu, Ag, Au, or their alloys, to absorb stray light and reduce electromagnetic interference, allowing for precise temperature monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical coupling is used between the thermal sensor and NFT for temperature monitoring, then temperature detection capability is provided, but background electromagnetic radiation creates unstable signals that reduce measurement accuracy
Solution Approach 1:
A shield structure is introduced as an intermediary element positioned between the thermal sensor and the NFT. This shield blocks background electromagnetic radiation from reaching the thermal sensor while allowing the evanescent wave coupling to continue, thereby eliminating the harmful background signal that degraded temperature measurement accuracy
Solution Approach 2:
The harmful background electromagnetic radiation is extracted or removed from the signal path by positioning the shield to block these external radiation sources. The shield selectively removes the unwanted background signal while preserving the necessary optical coupling between the NFT and thermal sensor, enabling accurate temperature monitoring
2Temperature
If the NFT operates at high temperatures for HAMR functionality, then heat-assisted magnetic recording is enabled, but the NFT reliability decreases due to thermal stress and potential failure
Solution Approach 1:
A feedback mechanism is established by using the thermal sensor to continuously monitor the NFT temperature and using this information to control the laser power. This closed-loop feedback allows the system to maintain the NFT at optimal operating temperatures, preventing excessive thermal stress that would reduce reliability while still enabling effective HAMR operation
Solution Approach 2:
Temperature monitoring and control measures are implemented in advance before NFT failure occurs. By continuously monitoring temperature and adjusting laser power proactively, the system prevents thermal damage to the NFT, thereby maintaining reliability during high-temperature HAMR operation
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 shield enables accurate detection of NFT temperature changes by minimizing background noise, thereby enhancing the reliability and performance of HAMR disk drives by reducing the impact of stray radiation on thermal sensor readings.
Implementation Method 1
A write head comprises a near-field transducer (NFT), a thermal sensor, and a shield disposed between the NFT and the thermal sensor, wherein the shield comprises a magnetic or conductive material
Implementation Method 2
A NFT may have a generally triangular output end, such that an evanescent wave generated at a surface of the waveguide couples to surface plasmons excited on the surface of the NFT
Implementation Method 3
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 4
To monitor the temperature of the NFT, HAMR disk drives may include a thermal sensor
Data Source
AI summary
Disclosed herein are write heads for data storage devices, methods for making and using such write heads, and data storage devices comprising such write heads. A write head comprises a near-field transducer (NFT), a thermal sensor, and a shield disposed between the NFT and the thermal sensor, wherein the shield comprises a magnetic or conductive material, such as, for example, Cu, Ag, Au, Al, Rh, Ti, Cr, Mo, Fe, Co, or Ni or an alloy that includes Cu, Ag, Au, Al, Rh, Ti, Cr, Mo, Fe, Co, and/or Ni. In some embodiments, the thermal sensor comprises a first lead and a second lead, and the shield is connected to the first lead but not the second lead to provide heat sinking for the shield.