Layered Waveguide TE to TM Mode Conversion for HAMR
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Solution Overview
Problem
Heat-assisted magnetic recording (HAMR) devices face challenges in converting transverse electric (TE) mode light to transverse magnetic (TM) mode for efficient energy delivery to magnetic media, limiting areal data density due to superparamagnetic effects.
Innovation Solution
A layered waveguide system is employed to convert TE mode light into TM mode by using two or more layers with varying cross-sectional areas along the light propagation direction, featuring a mode conversion region that rotates polarization from TE to TM mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional waveguide is used to deliver light in TE mode, then the structure is simple, but the energy delivery efficiency to magnetic media is insufficient due to inability to convert to TM mode
Solution Approach 1:
The waveguide is divided into multiple functional sections: an input section receiving TE mode light, a mode conversion section that transforms TE to TM mode through geometric transformation, and an output section delivering TM mode light to the media. This segmentation allows each section to be optimized for its specific function, achieving efficient mode conversion while maintaining overall system manageability.
Solution Approach 2:
The waveguide cross-sectional geometry is transformed from a first configuration suitable for TE mode to a second configuration suitable for TM mode. This dimensional transformation of the waveguide structure enables the mode conversion by changing the boundary conditions for electromagnetic wave propagation, thereby improving energy delivery efficiency without requiring complex external conversion devices.
2Productivity
If the waveguide cross track width is reduced to increase data density, then areal data density improves, but light propagation efficiency decreases
Solution Approach 1:
The waveguide cross-track width is made dynamic rather than static, varying along the propagation direction to match the requirements of different sections. The input section has a wider width for efficient TE mode coupling, while the output section has a narrower width for high data density, with a gradual transition in between. This dynamic geometry optimization allows the system to achieve both high light propagation efficiency and high areal data density.
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 layered waveguide effectively converts a significant percentage of TE mode light to TM mode, enhancing energy delivery to the magnetic media, thereby overcoming superparamagnetic limitations and increasing areal data density in HAMR devices.
Implementation Method 1
A layered waveguide is positioned between the input coupler and the NFT and configured to receive the light output from the input coupler in a transverse electric (TE) mode and deliver the light to the NFT in a transverse magnetic (TM) mode
Data Source
AI summary
An apparatus includes an input coupler configured to receive light excited by a light source. A near-field transducer (NFT) is positioned at a media-facing surface of a write head. A layered waveguide is positioned between the input coupler and the NFT and configured to receive the light output from the input coupler in a transverse electric (TE) mode and deliver the light to the NFT in a transverse magnetic (TM) mode. The layered waveguide comprises a first layer extending along a light-propagation direction. The first layer is configured to receive light from the input coupler. The first layer tapers from a first cross track width to a second cross track width where the second cross track width is narrower than the first cross track width. The layered waveguide includes a second layer that is disposed on the first layer. The second layer has a cross sectional area in a plane perpendicular to the light propagation direction that increases along the light propagation direction. The cross sectional area of the second layer is smaller proximate to the input coupler and larger proximate to the NFT.