Optical Spatial Mode Filter for HAMR TE00 Removal
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Solution Overview
Problem
Current heat-assisted magnetic recording (HAMR) technologies face issues with residual fundamental transverse electric (TE00) mode interference, which degrades recording performance and track density due to asymmetric adjacent track interferences and thermal background, especially when converting from TE00 to TE10 or TM00 modes, where imperfections in mode converters and polarization rotators lead to unwanted TE00 mode presence.
Innovation Solution
The implementation of an optical spatial mode filter using an array of plasmonic dipole antennas, periodic dielectric Bragg gratings, or multimode interference (MMI) splitters and combiners to selectively filter out the TE00 mode while allowing higher-order modes to pass through, minimizing insertion loss and maintaining performance across varying wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mode converters or polarization rotators are used to convert light from TE00 mode to TE10 or TM00 modes, then the light can be delivered to the near-field transducer for heating the recording medium, but residual fundamental TE00 mode components remain and degrade recording performance
Solution Approach 1:
The patent extracts and removes the harmful residual TE00 mode components from the light path using an optical spatial mode filter positioned between the mode converter/polarization rotator and the near-field transducer. This filter selectively eliminates the fundamental mode while allowing the desired higher-order modes (TE10 or TM00) to pass through, thereby resolving the contradiction by removing the harmful interference without affecting the useful light delivery function
Solution Approach 2:
The optical spatial mode filter acts as an intermediary component that mediates between the mode conversion stage and the near-field transducer. It selectively transmits desired modes while blocking residual fundamental mode components, thus improving recording performance without compromising the light delivery efficiency to the transducer
2Reliability
If an optical spatial mode filter is added to remove residual TE00 mode, then recording performance improves, but device complexity increases
Solution Approach 1:
The patent extracts only the essential filtering function from a potentially complex mode purification system. By using a relatively simple optical spatial mode filter rather than multiple complex mode converters or sophisticated control systems, the patent achieves improved recording performance while minimizing the increase in device complexity
Solution Approach 2:
The optical spatial mode filter serves as a compact intermediary that provides mode purification without requiring complex mechanical or electronic systems. This single-component approach adds minimal complexity to the overall device while effectively resolving the residual mode interference issue
3Reliability
If the optical spatial mode filter is highly selective to remove TE00 mode, then recording performance improves, but insertion loss of desired TE10 mode increases
Solution Approach 1:
The optical spatial mode filter is designed with local quality characteristics that are specifically optimized for the TE00 mode wavelength and spatial distribution. The filter's selective absorption or reflection properties are tailored to match the fundamental mode's unique characteristics, allowing it to reject TE00 components while transmitting the desired TE10 mode with minimal loss
Solution Approach 2:
The patent utilizes parameter changes in the optical filter's design, such as adjusting the grating period, depth, or material properties, to optimize the balance between TE00 mode rejection and TE10 mode transmission. By carefully tuning these parameters, the filter achieves high selectivity for the fundamental mode while maintaining low insertion loss for the desired higher-order modes
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 approach effectively reduces the TE00 mode by up to 50 times with minimal loss in the desired TE10 mode, improving recording performance, reducing thermal background, and enhancing wafer yield by ensuring low sensitivity to fabrication variations and wavelength changes.
Implementation Method 1
an optical spatial mode filter that prevents the remnant TE00 mode from affecting the recording performance while passing the light at the TE10 mode
Implementation Method 2
a near-field transducer that heats a recording medium in response thereto
Implementation Method 3
A mode converter is coupled to the first waveguide portion and configured to convert the light to higher-order transverse electric (TE10) mode
Implementation Method 4
A polarization rotator is coupled to the first waveguide portion and configured to convert the light to transverse magnetic mode (TM)
Implementation Method 5
a first waveguide portion configured to receive light from an energy source
Data Source
AI summary
A first waveguide portion receives light from an energy source in a fundamental transverse electric (TE00) mode. A mode converter converts a portion of the light to higher-order transverse electric (TE10) mode. A second waveguide portion receives the light at the TE10 mode and delivers the light to a near-field transducer that heats a recording medium in response thereto. An optical spatial mode filter prevents remnant light in the TE00 mode from affecting the recording medium while passing the light at the TE10 mode.