Dual-Grating Waveguide Coupler for EAMR Light Delivery
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Solution Overview
Problem
Energy-assisted magnetic recording (EAMR) heads face challenges in achieving high light coupling efficiency due to poor design of grating structures, leading to the need for costly high-power light sources and reliability issues related to heat, especially in high-volume manufacturing processes.
Innovation Solution
A dual-grating waveguide coupler is introduced, featuring a top grating and a bottom grating with specific periods and etch depths to maximize the coupling of electromagnetic radiation into the waveguide core layer, improving alignment and overall efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single grating structure is used to couple light into the waveguide, then the device complexity is low, but the coupling efficiency is poor requiring high-power light sources
Solution Approach 1:
The single grating structure is divided into two separate gratings: a first grating at the bottom interface and a second grating at the top interface of the waveguide core layer. Each grating is independently designed with specific period and etch depth to couple different portions of incident EM radiation, thereby improving overall coupling efficiency without requiring a single complex grating design
Solution Approach 2:
The coupling approach is extended from a single-plane grating to a multi-plane configuration by placing gratings at both the bottom and top interfaces of the waveguide core layer. This three-dimensional arrangement allows coupling of EM radiation from multiple directions and improves the capture percentage of incident radiation
2Loss of energy
If high-power light sources are used to compensate for poor coupling efficiency, then sufficient energy is delivered to the media, but heat-related reliability issues increase
Solution Approach 1:
The patent converts the previously harmful effect of poor coupling efficiency (which required high-power sources and generated excessive heat) into a benefit by designing optimized grating structures that achieve high coupling efficiency. This eliminates the need for high-power light sources and consequently reduces heat generation and heat-related reliability issues
3Ease of manufacture
If grating structures are designed to maximize coupling efficiency, then alignment difficulty in manufacturing is reduced, but the design complexity increases
Solution Approach 1:
The patent optimizes specific parameters of the grating structures, including period, etch depth, and positioning, to maximize coupling efficiency. By carefully selecting these parameters, the design achieves both high manufacturing ease through relaxed alignment tolerances and improved coupling performance, while the complexity is managed through systematic parameter optimization rather than complex geometric designs
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 dual-grating waveguide coupler enhances light coupling efficiency, reduces the need for high-power light sources, and mitigates heat-related reliability issues by capturing a higher percentage of incident radiation, enabling lower power consumption and improved thermal stability of magnetic grains.
Implementation Method 1
A grating structure may be used to couple the laser light into the waveguide
Implementation Method 2
The coupled light is then routed to a near field transducer by which the optical energy is provided
Data Source
AI summary
A magnetic head comprising a waveguide coupler for coupling incident electromagnetic (EM) radiation into a waveguide is disclosed. The waveguide coupler includes a bottom clad layer and a waveguide core layer formed above the bottom clad layer. An interface between the bottom clad layer and the waveguide core layer includes a first grating having a first period and a first etch depth, which are configured to couple a first portion of the incident EM radiation into the waveguide core layer. The waveguide coupler can further comprise a top clad layer formed above the waveguide core layer. An interface between the waveguide core layer and the top clad layer includes a second grating having a second period and a second etch depth. The second period and the second etch depth are configured to couple a second portion of the incident EM radiation into the waveguide core layer.