High Order Tapered Waveguide for HAMR Stability
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Solution Overview
Problem
Conventional heat assisted magnetic recording (HAMR) transducers face performance issues due to misalignments during fabrication, which affect the phase difference and efficiency of the interferometric tapered waveguide, leading to compromised light coupling at the near-field transducer.
Innovation Solution
The use of high order tapered waveguides with converging sides described by functions having terms greater than one, such as quadratic or cubic terms, which rapidly confine the laser mode to a smaller region closer to the geometric center, making the mode more stable and less sensitive to laser position changes, thereby maintaining antinode position at the near-field transducer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional linearly tapered waveguide is used, then the structure is simple and easy to manufacture, but the laser mode is not sufficiently confined and is highly sensitive to laser position misalignments
Solution Approach 1:
The patent changes the geometric parameters of the waveguide by transitioning from a linear taper (first-order polynomial) to a higher-order taper (second-order or higher polynomial). This parameter change in the taper profile enables stronger mode confinement and reduced sensitivity to misalignments while maintaining manufacturing feasibility through standard fabrication processes.
Solution Approach 2:
The patent applies curvature by using a higher-order polynomial function to describe the waveguide taper profile instead of a straight line. This curved, non-linear taper shape creates stronger evanescent field confinement and improves mode stability, effectively applying the principle of using curved geometries to enhance optical field confinement.
2Reliability
If the laser position shifts during fabrication, then misalignments occur between the laser and waveguide entrance, but the conventional waveguide cannot compensate for these misalignments
Solution Approach 1:
The patent modifies the waveguide's geometric parameters by implementing a higher-order taper profile that inherently provides greater tolerance to position variations. This parameter change in the taper order allows the system to maintain stable phase difference and antinode position even when laser alignment varies during manufacturing.
Solution Approach 2:
The higher-order taper design acts as a pre-designed compensation mechanism that anticipates and cushions against potential misalignments. By building in this geometric compensation beforehand, the system reduces the impact of fabrication tolerances on the final interference pattern and NFT coupling efficiency.
3Reliability
If a linearly tapered waveguide is used, then the mode confinement is weak, but stronger confinement is needed to maintain antinode position at the NFT
Solution Approach 1:
The patent changes the mathematical description of the taper profile from a linear function to a higher-order polynomial function. This parameter change in the taper order fundamentally alters the field distribution and confinement characteristics, providing stronger mode confinement that maintains antinode stability at the NFT location.
Solution Approach 2:
The patent employs a curved, non-linear taper profile described by higher-order polynomials to enhance the evanescent field interaction and mode confinement. This curved geometry creates stronger field confinement compared to the straight linear taper, effectively applying curvature principles to improve optical confinement.
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 design enhances the performance and reliability of HAMR transducers by stabilizing the laser mode propagation and improving energy coupling into the recording medium, even with potential misalignments during fabrication.
Implementation Method 1
high order tapered waveguides with converging sides described by functions having terms greater than one, such as quadratic or cubic terms, which rapidly confine the laser mode to a smaller region closer to the geometric center
Implementation Method 2
Where the light from the arms 24 and 26 recombines, an interference pattern is formed. An antinode in the interference pattern is at the conventional NFT 30.
Data Source
AI summary
A heat-assisted magnetic recording (HAMR) transducer is coupled with a laser for providing energy and has an air-bearing surface (ABS) configured to reside in proximity to a media during use. The HAMR transducer includes a write pole, at least one coil, and a tapered waveguide optically coupled with the laser. The write pole is configured to write to a region of the media. The coil(s) energize the write pole. The tapered waveguide includes an entrance distal from the ABS, a bottom proximate to the ABS, a first side and a second side opposite to the first side. At least a portion of the first side and the second side converge in accordance with a function having at least one term having an order greater than one.