Thermally-Assisted Magnetic Recording Head Mode Hopping Suppression
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Solution Overview
Problem
Conventional thermally-assisted magnetic recording heads experience significant power fluctuations due to mode hopping, leading to increased recording jitter, decreased signal-to-noise ratio, and adjacent track interference, which limits the achievable recording density.
Innovation Solution
The design of a thermally-assisted magnetic head with a laser unit and waveguide configuration where the longitudinal mode interval of the laser resonator is matched to within about 5% of an integer multiple of the optical interference period of the waveguide, stabilizing the light power by maintaining consistent optical interference conditions despite mode hopping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mode hopping occurs in the laser resonator, then the laser can operate at different wavelengths, but power fluctuations occur leading to increased recording jitter and decreased signal-to-noise ratio
Solution Approach 1:
The patent introduces a feedback mechanism where the waveguide structure provides optical interference feedback to the laser resonator. The waveguide length is specifically designed to provide feedback that compensates for mode hopping effects, stabilizing the output power while allowing wavelength flexibility. This feedback loop ensures that power fluctuations caused by mode hopping are suppressed.
Solution Approach 2:
The patent changes the physical parameter of the waveguide length to match the longitudinal mode interval of the laser resonator. By setting the waveguide length to be an integer multiple of the mode interval, the system transforms the mode hopping effect into a beneficial feedback mechanism that stabilizes power output. This parameter matching converts the harmful mode hopping into a useful stabilizing feedback.
2Reliability
If the waveguide length is increased to improve light guidance, then optical interference effects are enhanced, but mode hopping causes significant power fluctuations
Solution Approach 1:
The patent converts the harmful mode hopping effect into a beneficial feedback mechanism. By designing the waveguide length to match the laser mode interval, the mode hopping that would normally cause power fluctuations is transformed into a useful feedback signal that stabilizes the output. The harmful wavelength shifts become the basis for constructive feedback that maintains power stability.
3Productivity
If recording density is increased beyond 1 Tb/in2, then more information can be stored, but thermal vibration erases recorded information
Solution Approach 1:
The patent utilizes the phase transition concept by heating the magnetic medium locally during recording to temporarily change its magnetic properties. The medium is heated to a temperature where its coercive force decreases, allowing high-density recording, then cools to restore its high coercive force for stable storage. This phase transition approach enables both high density and stability.
Solution Approach 2:
The patent applies preliminary heating action before recording occurs. By pre-heating the local region of the magnetic medium, the coercive force is temporarily reduced, enabling the write head to form recording bits. After recording, the medium cools and its coercive force increases, preventing thermal vibration from erasing the data. This preliminary action enables high-density recording while maintaining stability.
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 configuration effectively suppresses power fluctuations, enhancing the performance of the thermally-assisted magnetic head by maintaining consistent recording conditions and improving recording density.
Implementation Method 1
a near-field light-generating element configured to produce near-field light when laser light is provided thereto to assist the main magnetic pole in writing data to the magnetic medium by heating a local region of the magnetic medium
Implementation Method 2
an interval of a longitudinal mode of the laser resonator is equal to within about 5% of an integer multiplier of an optical interference period of the waveguide
Implementation Method 3
a laser unit configured to produce a laser light, the laser unit having a laser resonator with a length (L1) in a direction parallel to laser light emission
Data Source
AI summary
In one embodiment, a device includes a laser unit configured to produce laser light, the laser unit having a laser resonator with a length in a direction parallel to laser light emission and a slider having a length in a direction perpendicular to a media-facing surface of the slider, the slider including a main magnetic pole configured to write data to a magnetic medium, a near-field light-generating element configured to produce near-field light when laser light is provided thereto to assist the main magnetic pole in writing data to the magnetic medium by heating a local region of the magnetic medium, and a waveguide configured for guiding the laser light to the element, the waveguide including a cladding surrounding a core, wherein an interval of a longitudinal mode of the laser resonator is equal to within about 5% of an integer multiplier of an optical interference period of the waveguide.