HAMR Recording Head External Cavity Laser for Optical Feedback Stability
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Solution Overview
Problem
Conventional lasers in heat-assisted magnetic recording (HAMR) devices experience instability due to optical feedback from the near-field transducer, leading to fluctuations in laser power and bit-error rate, which undermines areal density margin.
Innovation Solution
Incorporating a channel waveguide with a Bragg grating or using the near-field transducer as a reflector, closely spaced to function as a single optical entity, to minimize feedback and stabilize laser power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lasers are used in HAMR devices, then optical feedback from the near-field transducer occurs, but laser power stability deteriorates
Solution Approach 1:
The patent extracts the harmful optical feedback from the system by introducing an optical isolator that blocks reflected light from the near-field transducer from returning to the laser, thereby removing the destabilizing feedback path while preserving the useful optical energy delivery function
Solution Approach 2:
The optical isolator acts as an intermediary component between the laser and the near-field transducer, allowing forward light propagation while blocking reflected light, thus mediating the interaction to prevent harmful feedback without disrupting the primary function
2Reliability
If optical feedback is reduced, then laser power stability improves, but device complexity increases
Solution Approach 1:
The optical isolator serves as a compact intermediary device that provides feedback suppression in a space-efficient manner, integrating multiple optical functions (isolation, protection) into a single component that adds minimal structural complexity
Solution Approach 2:
The optical isolator provides self-regulating optical isolation that automatically blocks feedback light based on its inherent optical properties without requiring external control mechanisms, thereby maintaining stability without adding complex control systems
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
The solution effectively reduces optical feedback, stabilizing laser power and improving bit-error rate and areal density margin by integrating a Bragg grating within the external cavity laser, ensuring consistent optical energy delivery.
Implementation Method 1
The laser includes a Bragg grating within the channel waveguide and having a longitudinal axis defined along the light propagation direction. The Bragg grating is separated from the near-field transducer by 5 μm or less.
Implementation Method 2
The reflective back facet and the near-field transducer define a resonator of the external cavity laser.
Implementation Method 3
a channel waveguide that delivers light towards a media-facing surface of the recording head
Data Source
AI summary
An external cavity laser of a recording head includes a channel waveguide that delivers light towards a media-facing surface of the recording head. The laser includes an externally mounted part with an active region having a longitudinal axis corresponding to a light propagation direction of the channel waveguide. The externally mounted part has a reflective back facet and anti-reflective front facet. The laser includes a near-field transducer at an end of the channel waveguide proximate the media facing surface. The reflective back facet and the near-field transducer define a resonator of the external cavity laser.