LAUSR

We demonstrate that tunable whispering gallery modes can be supported in a spoof plasmonic cavity with a deep-subwavelength scale by inserting periodic metal strips into a silicon cylinder. The resonant frequencies of modes can be tuned freely by properly tailoring the structural parameters. Furthermore, we also show that the resonant modes can keep a high quality factor for a defect existing on the surface of the spoof plasmonic cavity by switching the whispering gallery resonance to Fabry–Perot-like resonance, which is absent for the traditional whispering gallery cavities. This property indicates potential applications in the design of optical cavities at low frequencies.