Terahertz microresonators for material characterisation

Terahertz (THz) technology is rapidly evolving, and the advancement of data and information processing devices is essential. Silicon THz microresonators provide perfect platforms to develop compact and integrated devices that could transform THz technology. Here we present a systematic study on the key figure of merit of silicon THz disc microresonators - the quality factor (Q-factor) - in dependence on the substrate's resistivity. Our results show that the Q-factor depends linearly on the resistivity and a variation in resistivity from 10k$\Omega$cm to 15k$\Omega$cm changes the Q-factor from 50k to 76k at 0.6THz. Moreover, we experimentally determine that the silicon material absorption is inversely proportional to the substrate's resistivity. In general, the presented methodology is ideally suited to precisely measure the material absorption of low-loss materials in the THz domain, which is challenging using conventional THz spectroscopy.