Resonant terahertz excitation and radiation from hierarchically-structured ZnO microspheres via a cylindrical cavity

Abstract

High-efficiency terahertz (THz) emission and detection are of great interest because of their promising applications in high-speed communications, biomedicine, and imaging. A previous study has achieved efficient room-temperature THz emission at ∼360 GHz by green-light exciting the lattice symmetric stretching vibrations of ZnO nanoplates self-assembled into ZnO microspheres (MSs). Herein, we explore resonant THz radiation of this kind of ZnO MSs under around 360 GHz excitation. A Fabry–Perot resonant cavity is designed and used to obtain the resonant THz signal. Compared to the case without the ZnO MSs, the THz output powers are enhanced by 1.5 and 3.2 times under two excitations of 356.1 and 375.8 GHz with an input power of 6.5 mW, respectively. Furthermore, it is shown that when a wide frequency THz wave irradiates on the ZnO MSs in the cavity, the output THz signal strength shows an obvious variation with frequency and can thus be utilized to detect the presence of some THz waves with specific frequencies. This work indicates that such self-assembled MSs can not only radiate the enhanced THz waves via a resonator, but also effectively apperceive some specific THz signals as a detector.