Dark Laser Heating by Forward Bias Pulse in HAMR
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Solution Overview
Problem
Heat-assisted magnetic recording (HAMR) drives face issues with 'mode hopping' due to temperature-induced changes in laser diodes, leading to inconsistent heating and reduced recording performance, as the laser diodes switch between different lasing modes, affecting the reliability and effectiveness of data writing.
Innovation Solution
A novel dark laser heating (DLH) technique using positive/forward bias pulses is employed to preheat the laser diode to a target temperature, with pulse durations shorter than the turn-on delay time, preventing optical output and minimizing the risk of data erasure or degradation, and this can be implemented with minimal hardware modifications using existing preamp IC technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the laser diode is heated to reduce coercivity for dense data writing, then recording density is improved, but temperature-induced mode hopping occurs leading to inconsistent heating and reduced reliability
Solution Approach 1:
The patent applies preliminary action by preheating the laser diode to a target temperature using a forward bias pulse before the actual write operation. This preheating stabilizes the laser diode temperature and prevents mode hopping during the write operation, ensuring consistent heating and reliable recording. The forward bias pulse is applied in advance to bring the laser diode to thermal equilibrium at the desired operating temperature.
Solution Approach 2:
The patent employs periodic action by using pulsed forward bias to heat the laser diode. Instead of continuous heating, a series of periodic forward bias pulses are applied to the laser diode to gradually raise its temperature to the target level. This periodic heating approach allows thermal management while maintaining stable operating conditions during data writing.
2Stability of the object's composition
If a forward bias pulse is applied to preheat the laser diode, then temperature stability is improved, but there is a risk of optical output causing data erasure or degradation
Solution Approach 1:
The patent applies parameter changes by carefully controlling the duration and amplitude of the forward bias pulse. The pulse width is specifically optimized to be sufficient to heat the laser diode to the target temperature but short enough to prevent lasing threshold activation. By adjusting these electrical parameters, the system achieves temperature stabilization without producing harmful optical output that could erase or degrade data.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining the laser diode at the target temperature through controlled forward bias pulsing. The heating action continues steadily until the desired temperature is reached and maintained, ensuring thermal stability throughout the write operation without interruption or harmful oscillations that could cause mode hopping.
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 stabilizes the laser diode's temperature, reducing the likelihood of mode hops and enhancing the reliability and consistency of HAMR recording performance by maintaining consistent heating and preventing accidental data erasure or overwrite.
Implementation Method 1
applying at least one forward bias pulse to the laser diode to preheat the laser diode to a target temperature
Data Source
AI summary
Various illustrative aspects are directed to a data storage device comprising a disk; a read/write head configured to read data from and write data to the disk; a laser diode configured to heat an area of the disk near the read/write head; and one or more processing devices configured to preheat the laser diode to a target temperature associated with a write operation, wherein the preheating comprises applying (e.g., using a preamplifier) at least one forward bias pulse to the laser diode, wherein a corresponding duration of the at least one forward bias pulse is shorter than a duration of a turn-on delay for the laser diode; and initiate a write operation for writing data to the disk, based at least in part on the preheating.