Cylindrical optical resonators: fundamental properties and bio-sensing characteristics

Abstract

In this paper, detailed theoretical analysis of cylindrical resonators is demonstrated. As illustrated, these kinds of resonators can be used as optical bio-sensing devices. The proposed structure is analyzed using an analytical method based on Lam's approximation. This method is systematic and has simplified the tedious process of whispering-gallery mode (WGM) wavelength analysis in optical cylindrical biosensors. By this method, analysis of higher radial orders of high angular momentum WGMs has been possible. Using closed-form analytical equations, resonance wavelengths of higher radial and angular order WGMs of TE and TM polarization waves are calculated. It is shown that high angular momentum WGMs are more appropriate for bio-sensing applications. Some of the calculations are done using a numerical non-linear Newton method. A perfect match of 99.84% between the analytical and the numerical methods has been achieved. In order to verify the validity of the calculations, Meep simulations based on the finite difference time domain (FDTD) method are performed. In this case, a match of 96.70% between the analytical and FDTD results has been obtained. The analytical predictions are in good agreement with other experimental work (99.99% match). These results validate the proposed analytical modelling for the fast design of optical cylindrical biosensors. It is shown that by extending the proposed two-layer resonator structure analyzing scheme, it is possible to study a three-layer cylindrical resonator structure as well. Moreover, by this method, fast sensitivity optimization in cylindrical resonator-based biosensors has been possible. Sensitivity of the WGM resonances is analyzed as a function of the structural parameters of the cylindrical resonators. Based on the results, fourth radial order WGMs, with a resonator radius of 50 μm, display the most bulk refractive index sensitivity of 41.50 (nm/RIU).

Hollow-Core Fiber-Based Biosensor: A Platform for Lab-in-Fiber Optical Biosensors for DNA Detection

“…In this scheme of detection, the bio/chemical analytes are directly detected without the laborious process of analyte molecule labeling [ 10 , 11 , 12 ]. Regarding their transducer part, optical biosensors are categorized into different groups of resonator-based [ 13 , 14 , 15 ], waveguide-based [ 16 , 17 ], and interferometric-devices based [ 18 , 19 ]. Although these optical sensors have demonstrated high sensitivities for both bulk and surface sensing measurements [ 20 , 21 , 22 ], they still suffer from a critical issue.…”

Fast analytical modelling of an SOI micro-ring resonator for bio-sensing application

“…In particular, it has been shown that whispering gallery mode (WGM) resonators like ring resonators can be used as label-free biosensors [10][11][12]. Other geometries of WGM-resonator-based biosensors, like spherical [13,14], cylindrical [15][16][17], and disk structures [18,19], have emerged as alternative device geometries in biosensing. While WGM microsphere and microcylinder biosensors exhibit high quality factors, their circuit integration, mass production and reproducibility are extremely challenging [13].…”

“…In our previously published works, we have presented a simple analytical method for modelling of cylindrical resonator based biosensors [16,17]. Here, we use some fast analytical methods to analyze a SOI WGM ring resonator coupled to a straight waveguide.…”