Filleted Corner Microresonators for Quality Factor
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Solution Overview
Problem
Existing optical microresonators, such as circular and square-shaped ones, face challenges with difficult fabrication, evanescent coupling, and low quality factors due to sharp corners, which limit their accuracy in nano-scale or micro-scale detection and optical resonance applications.
Innovation Solution
A microresonator with a polygonal shape and filleted corners, specifically a square microresonator with a central void and curved segments for evanescent coupling, is designed to enhance the quality factor and improve resonance conditions by reducing energy loss at sharp corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sharp-cornered polygonal microresonators are used, then fabrication is simplified, but quality factor decreases due to energy loss at sharp corners
Solution Approach 1:
The patent applies curvature by replacing sharp corners with filleted (rounded) corners in the polygonal microresonator. This curvature modification reduces optical energy loss at corner regions while preserving the overall polygonal geometry and fabrication advantages, thereby improving quality factor without sacrificing ease of manufacture
2Reliability
If circular microresonators are used, then quality factor is maintained, but fabrication difficulty increases
Solution Approach 1:
The patent segments the continuous circular geometry into a polygonal structure with straight sides and filleted corners. This segmentation approach maintains the quality factor benefits of curved geometries through filleting while simplifying fabrication by using straight-line segments that are easier to manufacture with standard lithography techniques
3Ease of operation
If evanescent coupling is implemented with curved resonator sidewalls, then coupling efficiency is achieved, but the tight submicrometer gap requirement increases device complexity
Solution Approach 1:
The patent applies local quality by implementing evanescent coupling specifically at the filleted corner regions where curvature naturally enhances coupling efficiency. This localized approach allows for more relaxed gap tolerances compared to straight sidewall coupling, reducing device complexity while maintaining coupling performance
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 filleted corner design significantly increases the quality factor of the microresonator, enabling more accurate detection and improved resonance conditions, making it suitable for advanced measurement and detection applications.
Implementation Method 1
An optical resonance occurs when light waves confined by total internal reflection in a closed loop dielectric microstructure are reflected back on the same optical path
Implementation Method 2
A shift in optical resonance frequency due to change in surrounding conditions has been used for different types of measurements and detections
Data Source
AI summary
The use of microresonators with sharp corners (rectangular and square-shaped) can be limited by severe energy loss at the corners. The effect of incorporating fillet design at sharp corners (rounding of corners) of such single mode optical microresonators is described. The effect on quality factor, free spectral range (“FSR”), and energy loss for varying values of fillet radii are quantified and compared with standard circular microring resonator. It is shown that the selection of optimum fillet radius for sharp-cornered microresonators provide higher quality factor than that of the conventional circular resonators.