HAMR Recording Head Mode Hopping Detection via On-Ramp Thermal Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mode hopping in heat-assisted magnetic recording (HAMR) devices causes abrupt changes in light intensity, leading to data loss or overwriting, making it difficult to quantify and measure mode hopping characteristics, especially during factory testing, which is time-consuming and expensive.
Innovation Solution
The recording head is moved onto a ramp to achieve high temperatures not attainable near the spinning disk, allowing for thermal isolation and characterization of mode hopping by monitoring temperature changes and sensor signals when the head is cooled by the disk, enabling faster and more cost-effective measurement of mode hopping frequencies and severities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the recording head is positioned near the spinning disk during normal operation, then the laser operates at stable operating temperature, but mode hopping cannot be characterized because the temperature range is limited
Solution Approach 1:
The patent applies preliminary action by pre-heating the recording head to high temperatures (e.g., 100°C or higher) before positioning it near the spinning disk. This allows the laser to be characterized across a broad temperature range during the pre-heating phase, and then the head is quickly positioned near the disk for operational testing. The preliminary temperature conditioning enables mode hopping characterization that would otherwise be impossible during normal operation near the disk.
2Measurement precision
If traditional factory testing methods are used to measure mode hopping characteristics, then comprehensive temperature coverage is achieved, but testing time and costs increase significantly
Solution Approach 1:
The patent replaces traditional mechanical temperature control systems (heaters, coolers, temperature chambers) with a method that utilizes the inherent thermal dynamics of the recording head when positioned near the spinning disk. The spinning disk's rotation creates natural cooling effects, and the system monitors mode hopping as the temperature naturally varies during head positioning and operation. This substitution eliminates complex temperature control hardware and significantly reduces testing time while maintaining measurement accuracy.
Solution Approach 2:
The system uses the spinning disk's natural rotation and the recording head's own operational heat generation to create the temperature variations needed for mode hopping characterization. The disk's rotation speed and the laser's power consumption naturally produce temperature changes that are sufficient to observe mode hopping events, eliminating the need for external temperature control systems or test equipment.
3Reliability
If the laser power is increased to compensate for mode hopping light intensity changes, then data writing reliability improves, but adjacent track overwriting risk increases
Solution Approach 1:
The patent implements feedback by continuously monitoring the laser's light intensity and detecting mode hopping events in real-time. When a mode hop is detected (identified by sudden changes in light intensity or wavelength), the system automatically adjusts the laser power or triggers a retry of the data writing operation. This feedback mechanism ensures data writing reliability without requiring permanent power increases, thereby avoiding adjacent track overwriting.
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 method allows for accurate characterization of mode hopping characteristics over a broader temperature range, reducing testing time and costs, and enables mitigation of mode hops during operation by storing and accessing critical temperatures to prevent data loss.
Implementation Method 1
A heating device is activated on the recording head to cause the recording head to obtain a high temperature that is not obtainable when proximate to the moving disk
Implementation Method 2
The recording head is moved over the moving disk such that the recording head reaches an operating temperature that is below the high temperature
Data Source
AI summary
A heat-assisted recording head is moved onto a ramp such that the recording head is thermally isolated from a moving disk. A heating device is activated on the recording head to cause the recording head to obtain a high temperature that is not obtainable when proximate to the moving disk. The recording head is moved over the moving disk such that the recording head reaches an operating temperature that is below the high temperature. One or more temperatures between the high temperature and the operational temperature are determined at which a laser of the recording head experiences mode-hopping. The one or more temperatures are stored and accessed by a controller to mitigate mode hopes during an operation of the recording head.