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Three-Dimensional Simulation of Particle-Induced Mode Splitting in Large Toroidal Microresonators
- Source :
- Sensors, Vol 20, Iss 5420, p 5420 (2020), Sensors (Basel, Switzerland)
- Publication Year :
- 2020
- Publisher :
- MDPI AG, 2020.
-
Abstract
- Whispering gallery mode resonators such as silica microtoroids can be used as sensitive biochemical sensors. One sensing modality is mode-splitting, where the binding of individual targets to the resonator breaks the degeneracy between clockwise and counter-clockwise resonant modes. Compared to other sensing modalities, mode-splitting is attractive because the signal shift is theoretically insensitive to the polar coordinate where the target binds. However, this theory relies on several assumptions, and previous experimental and numerical results have shown some discrepancies with analytical theory. More accurate numerical modeling techniques could help to elucidate the underlying physics, but efficient 3D electromagnetic finite-element method simulations of large microtoroid (diameter ~90 µm) and their resonance features have previously been intractable. In addition, applications of mode-splitting often involve bacteria or viruses, which are too large to be accurately described by the existing analytical dipole approximation theory. A numerical simulation approach could accurately explain mode splitting induced by these larger particles. Here, we simulate mode-splitting in a large microtoroid using a beam envelope method with periodic boundary conditions in a wedge-shaped domain. We show that particle sizing is accurate to within 11% for radii a<λ/7, where the dipole approximation is valid. Polarizability calculations need only be based on the background media and need not consider the microtoroid material. This modeling approach can be applied to other sizes and shapes of microresonators in the future.
- Subjects :
- Letter
02 engineering and technology
Discrete dipole approximation
whispering-gallery mode
lcsh:Chemical technology
01 natural sciences
Biochemistry
Resonance (particle physics)
Analytical Chemistry
010309 optics
large resonators
Resonator
particle sizing
mode splitting
Polarizability
0103 physical sciences
Periodic boundary conditions
lcsh:TP1-1185
Electrical and Electronic Engineering
Instrumentation
Physics
Computer simulation
021001 nanoscience & nanotechnology
Atomic and Molecular Physics, and Optics
Computational physics
finite-element method
Polar coordinate system
Whispering-gallery wave
0210 nano-technology
Subjects
Details
- Language :
- English
- ISSN :
- 14248220
- Volume :
- 20
- Issue :
- 5420
- Database :
- OpenAIRE
- Journal :
- Sensors
- Accession number :
- edsair.doi.dedup.....46c673ab3906a414a42f7f3b59418bbf