Multi-purpose Resistive Sensor for HAMR Laser Power Monitoring
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Solution Overview
Problem
Heat-assisted magnetic recording (HAMR) faces challenges in maintaining laser power stability due to space limitations, high power density, strong optical feedback, and environmental temperature variations, leading to inaccurate measurement methods that are not directly related to recording performance.
Innovation Solution
A multi-purpose resistive sensor is integrated into the HAMR head, comprising an air bearing surface section and a distal section that extends away from the near-field transducer (NFT), capable of detecting changes in output optical power and contact with the magnetic recording medium, while being situated in close proximity to the NFT without impacting optical and thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistive sensor is placed close to the NFT to monitor laser power, then measurement accuracy is improved, but the sensor may impact optical and thermal performance
Solution Approach 1:
The resistive sensor is divided into two distinct sections: an ABS section positioned at the air bearing surface and a distal section extending away from the NFT. This segmentation allows the sensor to monitor laser power fluctuations through the distal section while the ABS section maintains proper spacing from the NFT to avoid impacting optical and thermal performance.
Solution Approach 2:
Different sections of the resistive sensor are positioned in locations with different thermal and optical characteristics. The distal section is placed where it can detect laser power changes, while the ABS section is positioned to minimize interference with the NFT's optical and thermal performance, creating local quality variations throughout the sensor structure.
2Device complexity
If the resistive sensor is integrated into the HAMR head, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The resistive sensor is integrated directly into the HAMR head structure, merging the monitoring function with the existing head components. This consolidation reduces device complexity by eliminating separate monitoring devices while the sensor's dual-section design accommodates manufacturing tolerances through its distributed geometry.
Solution Approach 2:
The resistive sensor serves multiple functions: monitoring laser power fluctuations, detecting head-medium contact, and providing thermal characterization data. This multi-functionality reduces the need for separate components while the integrated design allows standard manufacturing processes to achieve required precision.
3Measurement precision
If the distal section extends lateral of or behind the NFT, then laser power monitoring is improved, but space limitations are exacerbated
Solution Approach 1:
The distal section of the resistive sensor extends in the down-track direction (behind the NFT) rather than only in the cross-track direction. This dimensional change allows the sensor to access regions with favorable thermal and optical characteristics for laser power monitoring while utilizing the down-track space that is less constrained than cross-track dimensions.
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 resistive sensor effectively monitors laser power fluctuations and head-medium contact, enhancing recording performance by providing accurate measurements and maintaining stable write width and magnetic transition location, thus reducing data errors.
Implementation Method 1
An optical waveguide is configured to couple light from a laser source to the NFT
Implementation Method 2
A resistive sensor comprises an ABS section situated at or proximate the ABS and a distal section extending away from the ABS
Implementation Method 3
A heat-assisted magnetic recording (HAMR) device uses a laser source and near-field transducer (NFT) to heat a spot on a magnetic disk
Data Source
AI summary
An apparatus comprises a slider having an air bearing surface (ABS) and a near-field transducer (NFT) at or near the ABS. An optical waveguide is configured to couple light from a laser source to the NFT. A resistive sensor comprises an ABS section situated at or proximate the ABS and a distal section extending away from the ABS to a location at least lateral of or behind the NFT. The resistive sensor is configured to detect changes in output optical power of the laser source and contact between the slider and a magnetic recording medium.