Tapered Waveguide Mode Conversion for HAMR Write Heads
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Solution Overview
Problem
Current heat-assisted magnetic recording (HAMR) devices face limitations in achieving high areal data density due to superparamagnetic effects, and existing write heads struggle to efficiently deliver energy to a small confined area on the magnetic media while maintaining a high temperature rise.
Innovation Solution
A write head with a near-field transducer and a waveguide that converts light from a fundamental transverse electric (TE00) mode to a transverse magnetic (TM00) mode, utilizing a core with tapered sections and different cladding layers to direct surface plasmons to the recording medium, enhancing energy delivery and localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional write heads are used to deliver energy to magnetic media, then the structure is simple, but the temperature rise in a small confined area is insufficient and superparamagnetic effects limit areal data density
Solution Approach 1:
The waveguide undergoes parameter changes through tapered sections that progressively reduce the core width, transforming the light mode from TE00 to TM00. This gradual geometric transformation enables efficient mode conversion and concentrates energy into a small confined area on the magnetic media, achieving high temperature rise necessary to overcome superparamagnetic effects and enable high areal data density
Solution Approach 2:
The waveguide structure implements local quality by creating different cladding layers (top, side, bottom) with different indices of refraction around the core. This localized variation in optical properties enables precise control of light propagation and mode conversion at specific locations, concentrating energy delivery to a small confined area while maintaining structural integrity
2Loss of energy
If a waveguide with tapered sections and different cladding layers is used to convert light mode and direct surface plasmons, then energy delivery efficiency is improved, but the device complexity increases
Solution Approach 1:
The waveguide is segmented into multiple functional sections: input section, first tapered section, straight section, second tapered section, and output section. Each segment performs a specific function in the mode conversion process, allowing systematic optimization of energy delivery while managing complexity through modular design
Solution Approach 2:
The waveguide employs composite material structure with different cladding layers (top, side, bottom) having different indices of refraction. This composite structure enables precise control of electromagnetic field distribution and mode conversion, improving energy delivery efficiency by minimizing losses during the TE00 to TM00 transformation while managing structural complexity through material property optimization
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 solution effectively increases areal data density by providing a high temperature rise in a small region on the media, overcoming superparamagnetic limitations and improving energy delivery efficiency.
Implementation Method 1
The waveguide is configured to receive light emitted from a light source at a fundamental transverse electric (TE00) mode. The waveguide is configured to deliver the light to the near-field transducer at a transverse magnetic mode (TM00)
Implementation Method 2
The waveguide comprises a core with first and second tapers separated by a straight portion of constant cross sectional width. The first and second tapers successively decrease a cross-sectional width of the core as it nears the near-field transducer
Implementation Method 3
The waveguide is configured to deliver the light to the near-field transducer at a transverse magnetic mode (TM00), which directs surface plasmons to a recording medium in response thereto
Implementation Method 4
The end portion comprises a top cladding layer on a first substrate-parallel surface of the core, a side cladding layer that encompasses sides of the core and a second substrate-parallel surface of the core, and a bottom cladding layer on the side cladding layer. The side cladding layer has a different index of refraction than the top and bottom cladding layers
Data Source
AI summary
An apparatus includes a write head comprising a near-field transducer at a media-facing surface of the write head and a waveguide extending along a light-propagation direction. The waveguide is configured to receive light emitted from a light source at a fundamental transverse electric mode. The waveguide is configured to deliver the light to the near-field transducer at a transverse magnetic mode which directs surface plasmons to a recording medium in response thereto. The waveguide comprises a core with first and second tapers separated by a straight portion of constant cross sectional width. The first and second tapers successively decrease a cross-sectional width of the core as it nears the near-field transducer. The waveguide includes an end portion between the second taper and the near field transducer. The end portion comprises a top cladding layer, aside cladding layer, and a bottom cladding layer on the side cladding layer.