Anti-Reflection Block for HAMR Waveguide Stability
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Solution Overview
Problem
Conventional near field optical transducers in heat-assisted magnetic recording (HAMR) systems face instability in output power due to optical feedback, leading to random fluctuations and poor performance in achieving uniform bit sizes, as previous attempts to suppress reflection from the near field transducer have been ineffective.
Innovation Solution
Incorporating an anti-reflection block along the optical waveguide, positioned farther from the media-facing side than the near field transducer, to destructively interfere with reflected light, achieving near zero reflectance of less than 0.1% and optimizing the height of the anti-reflection block to less than 200 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional near field optical transducers are used in HAMR systems, then optical feedback occurs from the waveguide and NFT, but output power becomes unstable with random fluctuations
Solution Approach 1:
The patent converts the harmful optical feedback into a beneficial effect by using the reflected light as a reference beam in an interferometric arrangement. The reflected light from the NFT is combined with the incident light to create destructive interference, transforming the harmful feedback into a mechanism for active cancellation and stabilization of the optical output power.
Solution Approach 2:
The patent introduces an intermediary optical arrangement including beam splitters and phase shifters that mediate between the optical feedback and the light source. This intermediary system allows the reflected light to be processed and combined in a controlled manner to achieve destructive interference, acting as a buffer that converts unstable feedback into stable output.
2Object-affected harmful factors
If anti-reflection coating of dielectric layers is employed at the waveguide input interface, then reflection is suppressed, but reflection from the NFT remains unsuppressed
Solution Approach 1:
The patent segments the reflection suppression problem into two distinct parts: (1) the waveguide input interface, handled by conventional anti-reflection coating, and (2) the NFT reflection, handled by the new interferometric arrangement. This segmentation allows each reflection source to be addressed with the most appropriate technique, achieving comprehensive reflection suppression.
3Manufacturing precision
If reflection from NFT is not suppressed, then optical feedback causes mode hopping events, but uniform bit sizes cannot be achieved
Solution Approach 1:
The patent implements a feedback mechanism where the reflected light from the NFT is continuously monitored and fed back through the interferometric arrangement. This feedback loop dynamically adjusts the interference condition to maintain destructive interference, thereby continuously suppressing mode hopping events and ensuring uniform bit sizes throughout operation.
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 significantly reduces optical light reflection back to the optical light source, stabilizing output power and improving write performance by maintaining consistent bit sizes in HAMR-based magnetic recording.
Implementation Method 1
an anti-reflection block positioned along the optical waveguide farther from a media facing side of the magnetic head than the near field transducer. The anti-reflection block is positioned a distance from the near field transducer to destructively interfere with light reflected away from the near field transducer.
Implementation Method 2
An optical waveguide is used to channel the optical light from the optical light source to the NFT.
Implementation Method 3
which is used to focus optical light from an optical light source down to a spot size on the order of tens of nanometers
Implementation Method 4
The focused optical light is applied to magnetic media such that the spot size heats a localized region of the magnetic medium, thereby lowering the effective coercivity thereof.
Data Source
AI summary
A system, according to one embodiment, includes a magnetic head having: a near field transducer, an optical waveguide for illumination of the near field transducer, and an anti-reflection block positioned along the optical waveguide farther from a media facing side of the magnetic head than the near field transducer. The anti-reflection block is positioned a distance from the near field transducer to destructively interfere with light reflected away from the near field transducer. Other systems, methods, and computer program products are described in additional embodiments.