Diffractive Waveguide Focusing for EAMR Near Field Transducer
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Solution Overview
Problem
Current methods for focusing a laser in Energy Assisted Magnetic Recording (EAMR) or Heat Assisted Magnetic Recording (HAMR) technology, such as mirror focusing, suffer from limited focus tightness and require improved solutions for precise light concentration on a near field transducer (NFT).
Innovation Solution
A focusing structure with an optically altered portion, featuring an array of localized optical alterations along a straight or curved surface within a waveguide, which diffractively focuses light into one or more focal points or zones, ensuring tight focusing and compact dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mirror focusing is used to focus laser to NFT, then focusing capability is achieved, but focus tightness is limited
Solution Approach 1:
The waveguide surface is segmented into multiple discrete zones that are selectively removed or modified. These segmented zones act as diffraction elements that collectively focus light onto the NFT, replacing the continuous mirror surface and achieving superior focus tightness through controlled light diffraction patterns
Solution Approach 2:
The mechanical mirror focusing system is replaced with an optical diffraction-based focusing mechanism. Instead of using a physical mirror to reflect and focus light, the invention uses diffractive optical elements formed by removing or modifying specific zones on the waveguide surface, substituting mechanical reflection with optical diffraction for enhanced focusing precision
2Measurement precision
If large optical quality boundaries are used to achieve tight focus, then focusing precision is improved, but device dimensions increase
Solution Approach 1:
The invention transitions from two-dimensional mirror surface reflections to three-dimensional diffractive zone structures within the waveguide. By utilizing vertical etching and multi-layer zone configurations, the system achieves tight focusing in a compact footprint, effectively adding a vertical dimension to the optical path control
3Ease of operation
If conventional focusing methods are used, then light can be focused to NFT, but phase control complexity increases
Solution Approach 1:
The invention changes the fundamental optical parameter from reflection angle control to diffraction order control. By modifying the physical dimensions and positions of the diffractive zones during fabrication, the focal properties are determined by geometric parameters rather than requiring complex real-time phase modulation, simplifying operational control
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 solution provides a high numerical aperture with compact dimensions, simplifies phase control and manufacturing, and achieves tight focus without the need for large optical quality boundaries, enhancing the ability to concentrate light precisely on the NFT for improved magnetic recording density.
Implementation Method 1
The altered portion comprises an array of localized optical alterations that alter the propagation of light through the focusing structure to diffractively focus the light as it exits the focusing structure
Data Source
AI summary
A focusing structure including an array of localized optical alterations that alter the propagation of light through the waveguide to diffractively focus the light as it exits the focusing structure. The array of optical alterations may be formed along either a straight or a curved line within a cross section of the focusing structure. In energy assisted magnetic recording apparatus a laser beam propagates through the waveguide to a near field transducer. The waveguide comprises a focusing element that includes an array of localized optical alterations that alter the propagation of the laser beam through the waveguide to diffractively focus the laser beam approximately at the near field transducer.