Waveguide Reflector for HAMR Head Light Recycling
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Solution Overview
Problem
Current heat-assisted magnetic recording (HAMR) technologies face inefficiencies due to mode leakage and scattered light, which increase head temperature and reduce coupling efficiency between the waveguide and near-field transducer, leading to higher effective currents and reduced reliability.
Innovation Solution
Incorporating a thin metallic reflector on the bottom side of the waveguide cladding, which blocks stray light, recycles power, and enhances coupling efficiency by redirecting out-of-plane scattering back to the near-field transducer, thereby reducing the effective current required for recording.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If no reflector is used in the waveguide, then the structure is simpler, but mode leakage and scattered light increase head temperature and reduce coupling efficiency
Solution Approach 1:
The patent converts the harmful effect of out-of-plane scattered light into a beneficial effect by introducing a reflector that redirects this scattered light back toward the near-field transducer. The scattered light, which would normally be lost and contribute to thermal heating, is now recycled to enhance the optical field at the transducer, improving coupling efficiency and reducing the effective current required for recording.
Solution Approach 2:
The reflector recovers the optical energy that would otherwise be discarded through mode leakage and scattered light. By positioning the reflector at the bottom of the waveguide cladding, the patent captures and redirects the scattered light back into the useful optical path, thereby recovering energy that would otherwise be lost to thermal heating and reducing overall system energy consumption.
2Loss of energy
If a reflector is added to block stray light, then coupling efficiency improves, but the waveguide structure becomes more complex
Solution Approach 1:
The reflector is implemented as a localized feature at the bottom of the waveguide cladding rather than a complete structural modification. This local placement allows the reflector to specifically address stray light blocking at the critical interface where scattered light would otherwise escape, while minimizing overall structural complexity and manufacturing difficulty.
3Productivity
If effective current is reduced through better coupling, then recording efficiency improves, but head temperature increases due to mode leakage
Solution Approach 1:
The patent converts the harmful thermal effect of mode leakage into a beneficial outcome by using the reflector to redirect the associated optical energy back to the near-field transducer. This recycling of optical energy enhances the useful recording function while preventing the energy from being lost as heat, thereby improving recording efficiency without the expected temperature penalty.
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 reflector design lowers the near-field transducer and miniSIM temperatures by >20K and >50K respectively, reduces effective current by >15%, and enhances field confinement, improving recording head reliability and efficiency.
Implementation Method 1
mode leakage and scattered light
Implementation Method 2
a reflector comprising a layer of metallic material... redirecting out-of-plane scattering back to the near-field transducer
Implementation Method 3
a channel waveguide extending to an air-bearing surface, where the waveguide comprises a core surrounded by cladding layers
Data Source
AI summary
A recording head comprises a waveguide extending to an air-bearing surface, and the waveguide comprises a core surrounded by cladding layers. A near-field transducer is disposed on a first side of the core, and a reflector, comprising a layer of metallic material, is disposed on a second side of the core facing away from the first side. The reflector extends beyond the core in a cross-track direction and extends in a direction normal to the air-bearing surface. The reflector has a thickness in a downtrack direction of less than 200 nm.