A high $T_{\mathrm{c}}$ superconducting terahertz emitter operated from 0.5 to 2.4 THz .*

According to our previous studies, the efficiency of the THz radiation from a high $T_{\mathrm{c}}$ superconducting emitter can be improved greatly when the stand-alone mesa structure of Bi2212 single crystal is used for the emitter$^{\mathrm{1)}}$. The principal reason for that lies in the heat removal from the mesa. Recently, we developed a new device structure with high heat exhaust from the stand-alone mesa structures and studied the radiation characteristics from the different shape of mesa structures. The results obtained from a cylindrical stand alone mesa show very wide the radiation frequencies ranging from 0.5 to 2.4 THz. Strong emission power peaks were observed at about 1.0 THz and 1.6 THz$^{\mathrm{2)}}$. 1) T. Kitamura \textit{et al.}, Appl. Phys. Lett. \textbf{105}, 202603 (2014) 2) T. Kashiwagi \textit{et al.}, Appl. Phys. Lett. \textbf{107}, 082601 (2015)