Asymmetric Taper Waveguide Coupler for Misalignment
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Solution Overview
Problem
Current waveguide input couplers in heat-assisted magnetic recording (HAMR) devices face significant performance gaps due to misalignment issues, particularly crosstrack direction misalignment, leading to inefficiencies in light coupling and mode conversion, resulting in lost light and increased stray radiation.
Innovation Solution
An asymmetric taper input coupler design is implemented, which transitions from a wider crosstrack dimension near the input surface to a narrower dimension away from it, enhancing mode conversion efficiency and reducing stray light by compensating for misalignment through targeted asymmetry and truncation, thereby improving coupling efficiency and reducing reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional symmetric input coupler is used, then the device structure is simple and easy to manufacture, but the coupling efficiency is low and misalignment tolerance is poor
Solution Approach 1:
The patent applies asymmetry by designing an input coupler with non-uniform width along its length, where the width varies according to a specific profile (e.g., wider at one end and narrower at the other). This asymmetric geometry optimizes the mode field distribution and improves coupling efficiency between the laser and waveguide, while also increasing tolerance to misalignment. The asymmetric profile is specifically tailored to match the mode field distribution of the laser output, thereby resolving the contradiction between simple structure and high coupling efficiency.
2Reliability
If the input coupler width is uniform, then the manufacturing process is simple, but the mode conversion efficiency is low and stray light is high
Solution Approach 1:
The patent applies local quality by varying the width of the input coupler at different positions along its length. Specifically, the coupler has a wider section near the laser input and a narrower section near the waveguide interface, with the width transitioning according to an optimized profile. This local variation in geometry optimizes the mode field distribution at each position, improving mode conversion efficiency and reducing stray light. The local quality approach allows the coupler to be tailored to the specific requirements of mode matching while remaining compatible with standard fabrication processes.
3Reliability
If a standard input coupler design is used, then the device is robust and easy to manufacture, but the tolerance to crosstrack misalignment is poor
Solution Approach 1:
The patent applies asymmetry by designing an input coupler with non-uniform width along its length, where the width varies according to a specific profile (e.g., wider at one end and narrower at the other). This asymmetric geometry optimizes the mode field distribution and improves coupling efficiency between the laser and waveguide, while also increasing tolerance to misalignment. The asymmetric profile is specifically tailored to match the mode field distribution of the laser output, thereby resolving the contradiction between simple structure and high coupling efficiency.
4Loss of energy
If the coupler has high coupling efficiency, then light loss is reduced, but the structure becomes more complex and requires precise fabrication
Solution Approach 1:
The patent applies local quality by varying the width of the input coupler at different positions along its length. Specifically, the coupler has a wider section near the laser input and a narrower section near the waveguide interface, with the width transitioning according to an optimized profile. This local variation in geometry optimizes the mode field distribution at each position, improving mode conversion efficiency and reducing stray light. The local quality approach allows the coupler to be tailored to the specific requirements of mode matching while remaining compatible with standard fabrication processes.
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 asymmetric taper input coupler significantly increases the conversion of light to higher-order modes, reduces unconverted light, and enhances tolerance to misalignment, resulting in improved coupling efficiency and stability, even under conditions of ±5 degrees crosstrack misalignment, while maintaining high performance at perfect alignment.
Implementation Method 1
The mode converter converts the light from a fundamental mode to a higher-order mode
Implementation Method 2
reduces unconverted light and enhances tolerance to misalignment, resulting in improved coupling efficiency and stability
Data Source
AI summary
An input waveguide is disposed on a substrate-parallel plane and configured to receive light from an input surface. A mode converter joins the input waveguide at a junction away from the input surface. The mode converter converts the light from a fundamental mode to a higher-order mode. An input coupler is proximate to and overlapping the input waveguide parallel to the substrate-parallel plane. The input coupler extending from the input surface to the mode converter and has an asymmetric taper that transitions from a wider crosstrack dimension near the input surface to a narrower crosstrack dimension away from the input surface.