Abstract-Subwavelength thick ultrahigh-Q terahertz disc microresonators

Dominik Walter Vogt, Angus Harvey Jones, Thomas Alan Haase, and Rainer Leonhardt

 (a) Schematic illustration of a THz disc resonator with subwavelength thickness. The insert depicts 2 orders of magnitude of the normalized electric field distribution of the fundamental TM mode of a disc resonator with 12 mm diameter and 66.5 μm thickness at 0.6 THz on a logarithmic scale. The HRFZ-Si disc is indicated with the grey solid line. (b) Simulated intrinsic 𝑄$Q$ factor 𝑄0$Q_0$ for two discs with 6 mm diameter and 72 μm thickness (blue dots) and 12 mm diameter and 66.5 μm thickness (orange dots). The green-shaded area indicates the 𝑄0$Q_0$ of a solid sphere with 6 mm diameter. For simplicity, a constant permittivity corresponding to a material absorption of 𝛼=0.006 cm−1$\alpha =0.006{\mathrm{cm}}^{-1}$ is assumed. (c) Optimal disc thickness (black) and maximal intrinsic 𝑄$Q$ factor (brown) for diameters from 6 to 60 mm at a design frequency of about 560 GHz. The green-shaded area shows the intrinsic 𝑄$Q$ factors for solid sphere resonators. (d) FSRs of the disc resonators for diameters from 6 to 60 mm with optimal thicknesses (blue) and solid spheres (green). The solid lines are interpolations of the simulated data points to guide the eye.

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-8-7-1183

Artificial structures that exhibit narrow resonance features are key to a myriad of scientific advances and technologies. In particular, exploration of the terahertz (THz) spectrum—the final frontier of the electromagnetic spectrum—would greatly benefit from high-quality resonant structures. Here we present a new paradigm of terahertz silicon disc microresonators with subwavelength thickness. Experimental results utilizing continuous-wave THz spectroscopy establish quality factors in excess of 120,000 at 0.6 THz. Reduction of the disc thickness to a fraction of the wavelength reduces the losses from the silicon substrate and paves the way to unparalleled possibilities for light–matter interaction in the THz frequency range.

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