Dual Thermal Sensor for HAMR Waveguide Power Monitoring
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Solution Overview
Problem
The challenge in thermally assisted magnetic recording (HAMR) is maintaining consistent optical power to ensure data stability and recording quality, as fluctuations in laser diode power due to mode hopping, temperature drift, and aging affect the heating temperature profile, leading to unreliable data storage.
Innovation Solution
A HAMR device equipped with two temperature sensors, a waveguide sensor and a reference sensor, positioned strategically to monitor and control optical power, allowing for precise feedback adjustments to maintain optimal recording conditions without additional optical components or assembly steps, thereby differentiating temperature variations caused by power fluctuations or slider flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical power from laser diode is used for HAMR recording, then heating temperature profile can be controlled to lower effective coercivity, but optical power fluctuates due to mode hopping, temperature drift, and LD aging leading to unreliable recording
Solution Approach 1:
The patent implements a feedback control system using temperature sensors to monitor the actual heating effect and adjust the optical power accordingly. The first temperature sensor monitors the heating region temperature, while the second sensor monitors ambient temperature, enabling real-time feedback to compensate for LD power fluctuations and maintain reliable recording
Solution Approach 2:
The system dynamically adjusts the optical power parameter based on temperature feedback to compensate for laser diode aging and drift. By changing the optical power parameter in response to temperature measurements, the system maintains stable heating effects despite LD parameter degradation over time
2Reliability
If temperature sensors are added to monitor optical power, then recording quality and reliability improve, but device complexity increases
Solution Approach 1:
The patent combines multiple temperature sensing functions into an integrated sensor system where two temperature sensors work together in a coordinated feedback loop. The first sensor monitors the heating region while the second monitors ambient conditions, merging their data to provide comprehensive temperature control that improves reliability without proportionally increasing complexity
Solution Approach 2:
The temperature sensors serve multiple functions: monitoring heating region temperature, measuring ambient temperature for compensation, detecting optical power levels indirectly, and providing feedback for both control and diagnostic purposes. This multi-functionality reduces the need for separate specialized components
3Measurement precision
If first temperature sensor is positioned close to waveguide for accurate monitoring, then temperature measurement precision improves, but sensor may be affected by laser light coherency interference
Solution Approach 1:
The patent uses the waveguide structure itself as an intermediary between the laser source and the temperature sensor. The waveguide confines and directs the optical energy, allowing the temperature sensor to measure the thermal effect indirectly while being protected from direct laser light interference. This intermediary approach enables precise temperature monitoring without exposing the sensor to harmful coherent light
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 solution enhances the reliability and longevity of HAMR devices by maintaining consistent optical power, improving recording quality and head lifetime through precise temperature control, while avoiding interference from laser light coherency.
Implementation Method 1
a first temperature sensor disposed adjacent the waveguide... The first temperature sensor has a length, a width and a thickness
Implementation Method 2
Heating of the media surface has been accomplished by a number of techniques such as focused laser beams or near-field optical sources
Implementation Method 3
a first temperature sensor disposed adjacent the waveguide... about two or more micrometers away from an air bearing surface
Implementation Method 4
a second temperature sensor disposed adjacent the waveguide... The second temperature sensor has a length, a width and a thickness
Data Source
AI summary
Embodiments of the present invention generally relate to a HAMR device having two temperature sensors. The first temperature sensor is disposed adjacent a waveguide and is about two or more micrometers away from an air bearing surface. The first temperature sensor has a length, a width and a thickness, and the length is greater than the width and the thickness. The length of the first temperature sensor is substantially perpendicular to the waveguide.