Fiber-Integrated Cylindrical WGM Resonator for Direct Light Coupling
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Solution Overview
Problem
Existing whispering gallery mode resonators are discrete optical devices that cannot be directly coupled with incident light, making them difficult to integrate into optical fiber systems, which limits their application in fields like micro-lasers and nonlinear optics.
Innovation Solution
A whispering gallery mode resonator based on a cylindrical cavity integrated within an optical fiber is fabricated using femtosecond laser etching and rapid hydrofluoric acid etching, allowing direct coupling of light propagating in the optical fiber core, with the cylindrical cavity being either smaller or larger than the fiber core depending on the fiber type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete microcavity types (microsphere, microbubble, micro-ring, etc.) are used for WGM resonators, then high Q-factor and narrow linewidth are achieved, but direct coupling with incident light radiation is not possible requiring external coupling schemes
Solution Approach 1:
The patent merges the WGM resonator cavity with the optical fiber by integrating the cylindrical cavity directly into the fiber core, eliminating the need for separate external coupling schemes. The light propagating in the fiber core directly couples to the cylindrical cavity, combining the light guidance function and resonance function into a single integrated structure.
Solution Approach 2:
The optical fiber serves multiple functions: it acts as both the light guidance medium and the housing structure for the WGM resonator. The cylindrical cavity integrated in the fiber core enables direct coupling while the fiber itself provides the coupling path, making the system multi-functional and eliminating additional coupling components.
2Ease of operation
If external coupling schemes (tapered fiber, side-polished fiber, waveguide, prism) are used to couple light to discrete WGM resonators, then light coupling is achieved, but integration into optical fiber systems becomes difficult
Solution Approach 1:
The patent combines the resonator cavity and the optical fiber into a single integrated structure, where the cylindrical cavity is formed within the fiber core. This merging eliminates the need for separate coupling schemes and enables direct integration into optical fiber systems, improving both ease of operation and adaptability.
3Ease of manufacture
If conventional etching methods are used for fabricating WGM resonators, then fabrication is possible, but integration with optical fiber and direct light coupling are not achieved
Solution Approach 1:
The patent uses femtosecond laser etching to directly fabricate the cylindrical cavity within the optical fiber core, replacing conventional mechanical or chemical etching methods. This enables precise three-dimensional structuring and direct integration of the resonator with the fiber, simplifying the overall device structure while maintaining ease of manufacture.
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 integrated resonator enables stable, low-cost, and high-Q factor performance, facilitating applications in micro-lasers and nonlinear optics with improved integration and simplicity in fabrication, as evidenced by a quality factor of 1.06×10^4, enhancing the potential of integrated optics.
Implementation Method 1
perform a femtosecond laser micromachining process... etching, by a femtosecond laser pulse, a ring structure with a required diameter on a surface of the optical fiber
Implementation Method 2
perform a corrosion process by using hydrofluoric acid solution... immersing a portion of the optical fiber body where the cylindrical structure is located in the hydrofluoric acid solution for corrosion
Implementation Method 3
the part of transmitted light beam of the optical fiber body is coupled to an inner wall of the cylindrical cavity in a tangential direction, and then periodically propagates on the inner wall of the cylindrical cavity to form a whispering gallery mode
Data Source
AI summary
A whispering gallery mode resonator based on a cylindrical cavity in an optical fiber and a fabrication method thereof are disclosed, which belong to the technical field of optical fiber application. The whispering gallery mode resonator includes an optical fiber body, a cylindrical cavity is provided in the optical fiber body, a top end of the cylindrical cavity is i open, and a bottom end of the cylindrical cavity is located inside the optical fiber body. Part or all of the cylindrical cavity blocks a part of transmitted beam of the optical fiber body, such that the part of the transmitted beam of the optical fiber body is coupled to an inner wall of the cylindrical cavity in a tangential direction, and then periodically propagates on the inner wall of the cylindrical cavity to form a whispering gallery mode.