Input Coupler Slanted Edge Diverts Stray Light
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Solution Overview
Problem
Heat-assisted magnetic recording (HAMR) devices face instability due to optical feedback from back-reflected light, causing laser instability and dynamic intensity noise, which results in sudden jumps and jitter in magnetic transitions recorded on discs.
Innovation Solution
An optical input coupler with a slanted edge and an escape slab is used to divert stray light, reducing back-reflections by guiding light into a waveguide core and directing uncoupled light away from the energy source, thereby stabilizing the laser operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional input coupler is used, then light coupling is achieved, but optical feedback from back-reflected light causes laser instability and dynamic intensity noise
Solution Approach 1:
The harmful back-reflected light is extracted and diverted from the waveguide core by introducing a slanted edge at the termination region of the input coupler. This slanted edge causes the uncoupled light to be directed away from the energy source, removing the optical feedback that causes laser instability.
Solution Approach 2:
The input coupler transitions from a symmetric rectangular cross-section to an asymmetric shape with a slanted edge at the termination region. This asymmetric geometry creates different optical paths for light propagation, enabling the diversion of back-reflected light while maintaining coupling functionality.
2Productivity
If the input coupler width is increased to capture more light, then coupling efficiency improves, but stray light and back-reflections increase
Solution Approach 1:
The input coupler employs local quality variation by having different cross-sectional shapes at different positions along its length. The wider section near the energy source maximizes light capture, while the slanted edge termination region diverts stray light, optimizing both coupling efficiency and reducing reflections locally.
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, improving laser stability and minimizing power jumps, with reflections decreased by up to 30% and further minimized with the addition of an escape slab, ensuring consistent magnetic recording.
Implementation Method 1
The input coupler has a first refractive index between that of the waveguide core and a surrounding material
Implementation Method 2
The input coupler is wider than the waveguide core and has a slanted edge at the termination region. The slanted edge crosses the waveguide core such that the input coupler narrows to a neck away from the waveguide core in a cross-track direction
Data Source
AI summary
A recording head has a waveguide core with an input end proximate an energy source at an input surface of the recording head. The waveguide core couples light from the energy source to a near-field transducer that heats a recording medium in response to the light. An input coupler extends along the waveguide core from the input end to a termination region that is away from the input end in a light propagation direction. The input coupler has a first refractive index between that of the waveguide core and a surrounding material. The input coupler is wider than the waveguide core and has a slanted edge at the termination region. The slanted edge crosses the waveguide core such that the input coupler narrows to a neck away from the waveguide core in a crosstrack direction.