Waveguide Core Notch for Stray Light Management in HAMR
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Solution Overview
Problem
In heat-assisted magnetic recording (HAMR) technologies, stray light propagation reduces efficiency and interferes with optical components, leading to inefficiencies in heating the magnetic medium and affecting data storage reliability due to high magnetic coercivity.
Innovation Solution
A waveguide with a core layer and a region of reduced downtrack thickness defined by a notch facing away from the near-field transducer, where the material of the notch has a different index of refraction than the core layer, is used to block stray light and enhance energy delivery to the near-field transducer, improving coupling efficiency and thermal gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a waveguide core layer is used to deliver energy to the near-field transducer, then energy delivery efficiency is improved, but stray light propagation interferes with optical components and reduces system efficiency
Solution Approach 1:
The patent converts the harmful stray light propagation into a beneficial structure by introducing a notch region that uses total internal reflection to redirect and contain stray light, transforming it into useful energy delivery paths that enhance coupling efficiency at the near-field transducer interface
Solution Approach 2:
The waveguide core layer is modified with a localized notch region having different refractive index properties than the surrounding core material. This local variation in optical properties creates total internal reflection at the notch interfaces, selectively managing stray light in the critical region near the transducer while maintaining standard waveguide functionality elsewhere
2Reliability
If high magnetic coercivity is used to overcome superparamagnetic effects, then data storage reliability is improved, but heating efficiency of the magnetic medium is reduced
Solution Approach 1:
The patent changes the optical parameters of the waveguide core layer by introducing a notch region with different refractive index. This parameter change creates total internal reflection that concentrates and redirects energy to the near-field transducer, thereby improving heating efficiency of the magnetic medium without requiring changes to the magnetic coercivity itself
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 configuration improves coupling efficiency, increases thermal gradients, and reduces erasure errors, leading to more reliable data storage by effectively focusing energy and minimizing stray light interference.
Implementation Method 1
A waveguide has a core layer extending from an energy source to the media-facing surface. The core layer includes a region of reduced downtrack thickness proximate the near-field transducer. The region of reduced downtrack thickness is defined by a notch facing away from the near-field transducer. A material of the notch has a different index of refraction than an index of refraction of the core layer.
Implementation Method 2
The energy causes a surface plasmon resonance of the near-field transducer to heat a magnetic recording medium.
Implementation Method 3
a small portion, or 'hot spot,' of the magnetic medium is locally heated to its Curie temperature, thereby allowing magnetic orientation of the medium to be changed at the hot spot
Data Source
AI summary
An apparatus includes a write pole proximate a media-facing surface of a recording head. A near-field transducer is adjacent to the write pole. A waveguide has a core layer extending from an energy source to the media-facing surface. The core layer includes a region of reduced downtrack thickness proximate the near-field transducer. The region of reduced downtrack thickness is defined by a notch facing away from the near-field transducer. A material of the notch has a different index of refraction than an index of refraction of the core layer.