Whispering Gallery Modes at THz

Abstract

Whispering gallery modes (WGM) offer strong confinement of electromagnetic radiation to specific resonances supported by the geometry of the resonator. In fact, highest ever quality factors are reported in optical and near‐infrared WGMs along with their applications. Terahertz (THz) radiation offers a unique spectroscopic window to probe materials and has applications in security, sensing, and telecommunication. WGMs at THz have untapped potential for light–matter interaction studies and wide‐ranging applications. In this review, an educational overview of WGMs is given, followed by a review of the THz WGMs and their applications.

On‐chip terahertz whispering gallery mode resonator with high‐Q based on multislot waveguide

“…[1][2][3][4] As a result, using resonators with higher quality factor and larger coupling spectrum width has been demonstrated as effect approach to improve the accuracy and range of THz sensors. [5][6][7][8][9][10][11][12] In past years, on-chip THz resonator and waveguide are widely used in the field of sensing and communication. 9,10,[13][14][15] With an increase interest in developing integrated THz devices and circuits, there is a compelling need for ultracompact on-chip THz resonators with high-quality factor and large coupling spectrum width.…”

“…[5][6][7][8][9][10][11][12] In past years, on-chip THz resonator and waveguide are widely used in the field of sensing and communication. 9,10,[13][14][15] With an increase interest in developing integrated THz devices and circuits, there is a compelling need for ultracompact on-chip THz resonators with high-quality factor and large coupling spectrum width. [7][8][9] Generally, high-resistivity float zone silicon (HRFZ-Si) ring cavity based on ridge waveguides are fabricated by CMOS technology.…”

“…9,10,[13][14][15] With an increase interest in developing integrated THz devices and circuits, there is a compelling need for ultracompact on-chip THz resonators with high-quality factor and large coupling spectrum width. [7][8][9] Generally, high-resistivity float zone silicon (HRFZ-Si) ring cavity based on ridge waveguides are fabricated by CMOS technology. 10,11 In this case, the performance of resonators is typically limited by a relatively large absorption loss (e.g., 0.025 cm −1 in 0.4 THz ~2 THz for HRFZ-Si, which is two orders of magnitude larger than the absorption loss of optical materials in near-infrared light).…”

“…To increase accuracy, sensitivity and range of THz sensors within ultracompact structure, higher-quality-factor and broad-spectrum on-chip THz resonators with bending radius down to few millimeter are still in great demand. 1,9,24 In this article, a novel scheme of on-chip THz WGMR with instinct quality factor up to 10 4 is presented when the bending radius is 2mm. And the coupling spectral width is increased to the order of 0.1THz at a fixed coupling distance.…”

Materials for Terahertz Optical Science and Technology

“…Whispering gallery mode (WGM) resonators offer another exotic platform to realize high Q-factor resonances at THz frequencies that enable capabilities for single molecule sensing with high specificity for medical, chemical and security applications, as discussed in the works reviewed by S. S. Prabhu and V. G. Achantha. [19] An alternative approach to enhance the device sensitivity is shown through total internal reflection of THz waves in a dielectric cavity that allows broadband imaging of cancer tissues, thin film sensing and holographic images (see the review on total internal reflection geometry from Q. Sun et al [20] ).…”