Ridge Waveguide Light Delivery to Near Field Transducer
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Solution Overview
Problem
Current methods for focusing optical energy into sub-50 nm spots for heat-assisted magnetic recording are inadequate, as solid immersion lenses and near field transducers are difficult to fabricate and result in diffraction-limited spot sizes greater than 80 nm, which is insufficient for high areal density magnetic recording.
Innovation Solution
A recording head with a write pole, return pole, and an optical near field transducer is used, where a waveguide delivers energy directly to the transducer, generating evanescent radiation that heats the magnetic storage medium, while the write pole affects magnetization, using a ridge waveguide or beveled waveguide to efficiently couple energy and achieve nano-scale spot sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solid immersion lenses or solid immersion minors are used to focus optical energy, then the spot size is reduced, but the spot size remains greater than 80 nm due to diffraction limits
Solution Approach 1:
A ridge waveguide is introduced as an intermediary component to transport optical energy from a remote source to the near-field transducer. The waveguide enables efficient energy coupling over extended distances while maintaining sub-diffraction spot sizes at the focal point, resolving the contradiction between achieving small spot sizes and the diffraction limits of conventional focusing methods.
Solution Approach 2:
The invention transitions from conventional 2D planar waveguides to a 3D ridge waveguide structure. This dimensional change enables better confinement of optical energy and more efficient coupling to the near-field transducer, achieving spot sizes below 80 nm by utilizing vertical dimension for mode confinement and energy transport.
2Use of energy by moving object
If solid immersion lenses and solid immersion minors are used, then optical energy can be focused, but fabrication becomes difficult
Solution Approach 1:
The optical system is segmented into distinct functional components: a remote optical energy source, a ridge waveguide for energy transport, and a near-field transducer for focal concentration. This segmentation allows each component to be optimized and fabricated independently using standard semiconductor manufacturing techniques, significantly easing the overall fabrication process compared to monolithic solid immersion lenses.
Solution Approach 2:
The invention replaces the mechanical focusing mechanism of solid immersion lenses with a waveguide-based energy transport system. The ridge waveguide uses evanescent field coupling and mode confinement to transport and deliver optical energy, eliminating the need for complex mechanical polishing and alignment required for solid immersion lens fabrication.
3Force
If conventional read/write heads with 2.4 T writer poles are used, then magnetic field generation is sufficient, but coercivity is too high to allow switching in materials with high Ku
Solution Approach 1:
The invention utilizes thermal phase transition (heating) to temporarily reduce the coercivity of high-Ku magnetic materials. By locally heating the recording medium with concentrated optical energy, the material transitions to a state with lower coercivity, enabling magnetic switching with available field strengths. After switching, rapid cooling restores high coercivity and ensures long-term magnetic stability.
Solution Approach 2:
The invention changes the temperature parameter of the magnetic material dynamically during the writing process. By controlling the local temperature through optical heating, the coercivity parameter is temporarily reduced to enable switching, then restored to high values for stability. This parameter modulation allows conventional 2.4 T writer poles to effectively switch high-Ku materials.
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 allows for efficient and compact fabrication of heat-assisted magnetic recording devices, enabling the creation of sub-100 nm spot sizes necessary for high areal density magnetic recording, overcoming the limitations of prior art by directly focusing energy onto the recording medium.
Implementation Method 1
directly focuses the energy on the near field transducer that causes the near field transducer to emit evanescent radiation
Implementation Method 2
heats a portion of the magnetic storage medium
Implementation Method 3
a write field produced by the write pole affects the magnetization of the portion of the magnetic storage medium
Implementation Method 4
A waveguide is provided for delivering optical energy directly to the near field transducer
Data Source
AI summary
A magnetic recording head comprises a write pole having a pole tip adjacent to an air bearing surface, a return pole, an optical near field transducer positioned adjacent the pole tip and an air bearing surface for exposing a portion of a magnetic storage medium to high energy radiation. The energy is directly provided to the near field transducer by a ridge waveguide with tapered coupling elements, by a two dimensional straight or curved waveguide with a beveled end with a metal/dielectric coating for delivering energy to the near field transducer, or by a curved waveguide. The waveguide with tapered coupling elements or with beveled end can be fabricated by means of conventional wafer processing.