HAMR Thermal Sensor Optical Power Monitoring
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Solution Overview
Problem
In heat-assisted magnetic recording (HAMR) technologies, monitoring the optical intensity of light delivered by a light source is crucial for ensuring reliable recording, but variations in manufacturing processes and operational conditions lead to inconsistencies in optical power, affecting the reliability and yield of HAMR transducer design and manufacturing. Additionally, thermal heating from the light source causes slider deformation, altering head-media clearance over time.
Innovation Solution
An apparatus and method utilizing a thermal sensor situated on the slider, either outside the light path or directly in the path but not at the intended focus, to measure changes in temperature resulting from direct light source heating, allowing for the monitoring of optical intensity and accounting for thermally induced slider deformation. This involves using a biased resistive sensor to determine the magnitude and rate of optical power delivery and deformation, enabling calibration and adjustment of light source output during manufacturing and field use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermal sensor is placed in the light path to monitor optical intensity, then measurement precision is improved, but the thermal sensor is exposed to direct light heating which complicates distinguishing waste heat effects
Solution Approach 1:
The patent divides the thermal sensing function into two separate sensors: one positioned in the light path to detect total heating (light heating + waste heat), and another positioned outside the light path to detect only waste heat. This segmentation allows the system to separately measure and differentiate between light source heating and waste heat effects, resolving the complexity of distinguishing these thermal sources while maintaining measurement precision.
Solution Approach 2:
The patent uses the thermal sensor positioned outside the light path as an intermediary measurement point that detects waste heat independently. This intermediary sensor provides a reference measurement that can be used to subtract waste heat effects from the total heating measured by the sensor in the light path, thereby isolating the optical intensity component without requiring the primary sensor to directly distinguish between heat sources.
2Ease of manufacture
If the thermal sensor is positioned outside the light path, then waste heat measurement is simplified, but direct optical intensity monitoring capability is reduced
Solution Approach 1:
The patent combines the measurements from two thermal sensors positioned at different locations: one in the light path and one outside. By merging these two measurement signals, the system achieves both simplified waste heat measurement (from the external sensor) and accurate optical intensity monitoring (from the combined data), resolving the trade-off between ease of manufacture and measurement precision.
Solution Approach 2:
The patent implements a feedback mechanism where the thermal sensor positioned outside the light path provides continuous waste heat measurement data. This feedback is used to compensate for waste heat effects in the optical intensity measurement, allowing the system to maintain measurement precision while using the simpler external sensor positioning for waste heat characterization.
3Reliability
If multiple thermal sensors are used to distinguish light heating from waste heat, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by positioning thermal sensors at specific locations with distinct thermal characteristics: one sensor in the light path where both light heating and waste heat are present, and another outside the light path where only waste heat is present. This localized positioning allows each sensor to measure specific thermal components, improving reliability through differentiated measurement points while keeping the overall system relatively simple.
Data Source
AI summary
A light source is configured to produce light, a waveguide is optically coupled to the light source and configured to direct the light to an intended focus location, and a slider is configured to use the light as an energy source for heating a region of a magnetic recording medium. A thermal sensor is situated on the slider at a location outside of a light path that includes the intended focus location. The thermal sensor is configured for sensing a short time constant change in temperature resulting from light source heating of the thermal sensor, wherein the sensed change in thermal sensor temperature is representative of optical intensity of the light delivered to the intended focus location.