Anomalous blue-shift of terahertz whispering-gallery modes via dielectric and metallic tuning

Abstract

The vast majority of resonant systems show a red-shift for the resonance frequency when a perturbation, e.g. losses, are introduced to the system. In contrast, here we report for the first time the experimental demonstration of both red-and anomalous blue-shifting of whispering-gallery modes (WGMs) using dielectric and metallic substrates. The maximum blue-shift is more than three times as large as the expected red-shift, proving that the anomalous blue-shift is more than a peculiar curiosity. The experiments are performed in the terahertz (THz) frequency range with coherent continuous-wave spectroscopy. The results establish dielectric and metallic tuning as a novel, and viable approach to tune high quality (high-Q) WGMs, and provide valuable insights into the anomalous blue-shift of WGM cavity systems. The tuning capabilities for these compact monolithic resonators is of significant interest for fundamental science and technological applications alike.

Symmetry-Broken High-Q Terahertz Quasi-Bound States in the Continuum

“…We observe a high- Q quasi-BIC resonance with an experimentally measured quality factor of Q = 3700 ± 200. Other works in the THz regime have also achieved very high Q modes. − However, to our knowledge, this represents a remarkable accomplishment, establishing a new benchmark for the highest reported experimental Q factor for a quasi-BIC resonance supported by an all-dielectric THz metasurface. This work opens up a practical path for developing high- Q metasurfaces suitable for THz applications.…”

Microresonator frequency reference for terahertz precision sensing and metrology

“…Analysing the intensity ratio and phase difference of the reference scan and sample scan allows to extract the frequency difference between the THz sensor (for this particular tilt and coupling position) and the frequency reference. Because the loaded resonance frequency of the THz microresonator sensor shows a small dependence on the coupling position (<5 MHz) [15], and to improve the accuracy of the measurements, we extract the resonance frequencies for several coupling positions at various distances to the waveguide. In particular, the resonance frequency shift follows an exponential behaviour as a function of the distance between the micoresonator and waveguide [16].…”

Crystalline Hydrate Dehydration Sensing Based on Integrated Terahertz Whispering Gallery Mode Resonators

“…Terahertz resonators can be used for sensing and have the advantages of high accuracy and integration. Similar methods mainly focus on the terahertz whispering gallery mode resonators (THz-WGMRs) [ 33 , 34 , 35 , 36 , 37 ], metasurfaces [ 38 , 39 , 40 , 41 ], and photonic crystals [ 42 , 43 , 44 ]. THz-WGMRs possess high sensitivity because of high Q factors.…”