Laser Write Power Mode Hop Compensation in HAMR
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Solution Overview
Problem
Data storage devices face challenges in maintaining consistent head positioning and fly height during write operations due to self-heating effects, leading to mode hops in laser output power, which affect data quality and reliability.
Innovation Solution
A mode hop map is generated and used to adjust laser write power and fly height actuator power in real-time, compensating for mode hops through incremental adjustments and 'fat pulse' techniques, ensuring consistent head positioning and fly height during write operations across varying temperatures and write powers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser write power is increased to improve data writing quality, then write quality improves, but self-heating effects cause mode hops that worsen positioning stability
Solution Approach 1:
The system performs preliminary characterization of the laser's mode hop behavior across different temperature and power conditions, storing this information in a mode hop map. This pre-characterization allows the system to anticipate and compensate for mode hops before they occur during actual data writing operations, thereby maintaining both write quality and power stability.
Solution Approach 2:
The system continuously monitors laser output power and temperature, using this feedback to dynamically adjust laser write power based on the pre-characterized mode hop map. This closed-loop feedback mechanism ensures that the laser operates in stable regions while maintaining optimal write quality, resolving the contradiction between power increase and stability.
2Stability of the object's composition
If laser write power is adjusted in real-time to compensate for mode hops, then power stability improves, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The complex task of characterizing mode hop behavior is performed once during system initialization or manufacturing, with results stored in a lookup table (mode hop map). This preliminary action converts a potentially complex real-time control problem into a simpler table-lookup and adjustment operation, reducing ongoing computational complexity while maintaining power stability.
Solution Approach 2:
The system uses its own operational data (temperature, power levels, observed mode hops) to automatically build and refine its own mode hop map without external intervention. This self-characterization capability reduces the need for external calibration equipment and simplifies the overall control architecture while achieving stable laser output.
3Reliability
If mode hop compensation is implemented to maintain data quality, then data reliability improves, but energy consumption increases due to additional adjustments
Solution Approach 1:
The mode hop map is pre-computed and stored, allowing the system to quickly determine appropriate power adjustments without performing complex real-time analysis. This preliminary preparation minimizes the computational energy required during actual data writing operations while maintaining high data reliability through accurate compensation.
Solution Approach 2:
The system changes laser operating parameters (power level, pulse duration) based on pre-characterized mode hop patterns rather than continuously adjusting parameters in real-time. This discrete parameter change approach, guided by the mode hop map, achieves reliable data writing with lower energy consumption compared to continuous fine-tuning.
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 approach effectively compensates for mode hops, maintaining data quality and reliability by adjusting laser write power and fly height actuator power, thereby stabilizing the head positioning and fly height, even under varying conditions.
Implementation Method 1
Heat assisted magnetic recording (HAMR) is a recent development that improves the quality of written data by heating the disk surface during write operations in order to decrease the coercivity of the magnetic medium
Implementation Method 2
self-heating effects, leading to mode hops in laser output power
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a recording medium, wherein the head comprises a laser configured to heat the recording medium. A mode hop map is generated for a write power applied to the laser during a write operation. The write power is applied to the laser during the write operation and the write power is adjusted in response to the mode hop map.