Polarization Rotator Waveguide for TAMR Head Lifetime
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Solution Overview
Problem
Current thermally assisted magnetic recording (TAMR) heads suffer from short lifetimes due to resistive heating, which degrades materials in the plasmon generator and surrounding cladding layers, limiting the reliability and longevity of the recording technology.
Innovation Solution
The introduction of a waveguide structure that polarizes transverse electric (TE) light to transverse magnetic (TM) light mode within a polarization rotator section, allowing for the efficient conversion of TE light to TM light before it reaches the plasmon generator, thereby reducing resistive heating and increasing the TAMR head's lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TM light at wavelengths near 800 nm is used in the waveguide, then surface plasmon excitation is efficient, but resistive heating degrades materials such as Au in the plasmon generator, alumina in the cladding layer, and FeCo/NiFe in the writer pole, resulting in short lifetime
Solution Approach 1:
The patent changes the wavelength parameter of the light source from near 800 nm to above 800 nm (e.g., 850 nm, 900 nm, 940 nm, 980 nm), which fundamentally alters the resistive heating characteristics. This parameter change reduces resistive heating in the plasmon generator and surrounding materials, thereby extending the lifetime of the TAMR head while maintaining surface plasmon excitation efficiency
Solution Approach 2:
The patent employs a composite waveguide structure with specific material combinations (e.g., silicon nitride core with alumina cladding, or silicon core with silicon nitride cladding) that are optimized for both optical performance and thermal resistance. These composite structures reduce resistive heating effects while maintaining the necessary optical properties for surface plasmon excitation at wavelengths above 800 nm
2Ease of manufacture
If TE light from laser diode is directly coupled to waveguide, then coupling is simple, but TM polarization mode is required for efficient surface plasmon excitation
Solution Approach 1:
The patent introduces a polarization conversion structure as an intermediary component between the TE light source and the waveguide. This intermediary converts the TE polarization mode to TM polarization mode, enabling efficient surface plasmon excitation while maintaining the simplicity of TE light source coupling. The conversion structure acts as a mediator that reconciles the polarization mismatch between the laser diode output and the waveguide requirement
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 significantly extends the lifetime of the TAMR head by reducing thermal degradation of components and improving the reliability of the recording technology, enabling higher data densities and longer operational periods.
Implementation Method 1
TE light from a laser diode (LD) is directed into a back end of a waveguide and then polarized to a TM light mode before reaching a front section of the waveguide
Implementation Method 2
The waveguide receives TE light from a light source and then delivers a substantial portion of the input light energy in a TM mode by coupling to a near field device (PG) where a surface plasmon mode is excited
Implementation Method 3
TE light from a laser diode (LD) mounted on a slider by an end-fire butt coupling is coupled to a waveguide
Data Source
AI summary
A process sequence for forming a waveguide structure with a light polarization rotator section that converts transverse electric light from a TE light source to transverse magnetic light which is subsequently coupled to a plasmon generator (PG) is disclosed. The light polarization rotator section has a length determined by TE LD light wavelength, and the effective mode index of the two orthogonal fundamental modes, and a slope is formed in one side of the symmetric structure with a 45 degree angle with respect to a bottom surface. Offsets that narrow the cross-track width may be formed on the two sides of the light polarization rotator section to improve symmetry for higher TE to TM polarization conversion efficiency.