Direct observation of THz radiation from cylindrical structure of intrinsic Josephson junction system of Bi2212

Intense terahertz (THz) radiation was observed from a single crystalline high-$T_{c}$ superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ (Bi2212) system$^{1, 2)}$. We have performed various experiments on THz radiation with Bi2212 rectangular mesa structure fabricated by Argon-ion-milling and photolithography technique with changing the sample parameters. In this work, we report new experimental results obtained with samples which have a cylindrical structure fabricated by focused ion beam milling. The intense emission of electromagnetic radiation can be obtained in the return blanch only. The frequency is directly measured by FT-IR spectrometer to be $f$ = 0.474 THz in this particular sample of diameter with 90 $\mu $m. This frequency value is in good agreement with the fundamental cavity resonance mode frequency. 1) L. Ozyuzer et al., Science \textbf{318} (2007) 1291 2) K. Kadowaki et al., Physica C \textbf{468} (2008) 634-639