Whispering-gallery-mode sensors for biological and physical sensing

Abstract

The term whispering gallery modes (WGMs) was first introduced to describe the curvilinear propagation of sound waves under a cathedral dome. The physical concept has now been generalized to include light waves that are continuously reflected along the closed concave surface of an optical cavity such as a glass microsphere. The circular path of the internally reflected light results in constructive interference and optical resonance, a morphology-dependent resonance that is suitable for interferometric sensing. WGM resonators are miniature micro-interferometers that use the multiple-cavity passes of light for very sensitive measurements at the micro-and nanoscale, including single molecules and ions measurements. This Primer introduces various WGM sensors based on glass microspheres, microtoroids, microcapillaries and silicon microrings. We describe the sensing mechanisms including mode splitting and resonance shift, exceptional-point-enhanced sensing, and optomechanical and optoplasmonic signal transductions. Applications and experimental results cover in-vivo and single-molecule sensing, gyroscopes and microcavity quantum electrodynamics. Data analysis methods and limitations of the WGM techniques are also discussed.Finally, we provide an outlook for molecule, in-vivo and quantum sensing.

Rapid detection of an Ebola biomarker with optical microring resonators

“…We utilized a silicon photonic microring resonator platform for the detection of sGP. Microring resonators operate on the principle of WGM sensing and continue to be a promising layout for biosensing applications due to ease of fabrication, chip integration, and high multiplexing potential ( Figure S1 ) ( Jiang et al., 2020 ; Yu et al., 2021 ). Light at a specific resonant wavelength is confined in small microring cavities.…”

Thermo-Optical Sensitivity of Whispering Gallery Modes in As2S3 Chalcogenide Glass Microresonators

“…From here it is obvious that η = (2ξ/d) 2 , where ξ is a root of ξ ≈ 0.8521•tan ξ. The smallest root ξ ≈ 0.656 was chosen, as it corresponds to the slowest cooling harmonic (without any radial variations in ∆T), which is most likely to occur in our system.…”

“…Dielectric microresonators with whispering gallery modes (WGMs) have plenty of diversified applications [1], among which sensing applications play a significant role [2][3][4][5][6][7][8][9][10][11]. Microresonators with certain advantages and disadvantages are produced from different materials using special technologies [12].…”

The missing link between standing- and traveling-wave resonators

“…In terms of applications, this can be useful in a number of ways. For instance, the larger splitting in the location of the field maxima in the standing-wave zone can be utilized for selective sensing by functionalizing [46] this exact location with receptors that can bind only to a particular molecule while at the same time use the traveling-wave zone for excitation and collection. On the other hand, one can instead use both zones for detecting the presence of more than one molecule (but only one at a time).…”