Recent Progress on Optoplasmonic Whispering‐Gallery‐Mode Microcavities

Abstract

Optoplasmonic whispering‐gallery‐mode (WGM) microcavities, consisting of plasmonic nanostructures and optical microcavities, provide excellent platforms for exploring fundamental mechanisms as well as facilitating novel optoplasmonic applications. These integrated systems support hybrid modes with both subwavelength mode confinement and high‐quality factor which do not exist in either pure optical WGM microcavities or plasmonic resonators. In this progress report, geometric designs and fabrication strategies of optoplasmonic microcavities, which efficiently bridge the interaction between resonant light and plasmonic resonances, are reviewed in detail. Three types of hybrid modes in the optoplasmonic microcavities, that is, surface‐plasmon‐polariton whispering‐gallery modes, hybrid photon–plasmon whispering‐gallery modes, and heterostructured metal–dielectric whispering‐gallery modes, are considered. These modes are characterized by a largely enhanced evanescent field that is referred to as a plasmon‐type field in hybrid whispering‐gallery modes. Moreover, the coupling effect between localized surface plasmon resonances and whispering‐gallery modes is summarized. The underlying coupling mechanisms and their influence on mode shifts, Q factor, mode splitting, and line shapes of the whispering‐gallery modes are discussed. Applications based on optoplasmonic WGM microcavities including enhanced sensing, nanolasing, and free‐space coupling are highlighted, followed by an outlook of the opportunities and challenges in developing large‐scale on‐chip integrated optoplasmonic systems.

Fabrication and characterization of on-chip silicon spherical-like microcavities with high Q-factors

“…sphere-like microcavity are observed as the corresponding Lorentzian dip families in the shown spectrum. The Q-factor is defined as the ratio of the energy stored in the oscillating cavity to the energy dissipated per cycle by damping processes [32] , which can be expressed by Q = λ=Δλ, where λ is the central wavelength of a WGM, and Δλ is its full width at half-maximum. Due to the large effective index mismatch between the WGMs of this silicon microcavity and the silica fiber taper, the resonance mode is under coupled, and its strength is relatively weak.…”

4D Printing of Liquid Crystals: What's Right for Me?

“…Since the cavity's functionality relies on the shift of the resonance frequency, WGM microcavities are attractive as optical sensors. [184] When the waveguide itself was partially made of LCN, the WGM resonance was blue shifted upon illumination (Figure 10g). [167] In contrast, if the WGM was instead made of a nonresponsive material and coupled to an LCN which was then actuated, the shape of the passive WGM changed, and red shifted the resonance.…”

Methods in Raman spectroscopy for saliva studies – a review

“…Nanosystems combining photonic and plasmonic components have recently found sensing applications, [350] notably whispering gallery mode sensors. [351] In a Raman-saliva context, Hong et al [195] have presented an optical-plasmonic hybrid FDTD model consisting of an AuNP underlayer and a larger silica microsphere (Figure 7C). The authors measure methamphetamine-doped urine and saliva with the optoplasmonic arrangement, presenting spectra down to concentrations of 1 Â 10 À8 M and 1 Â 10 À9 M, respectively.…”