Terahertz emission from a stack of intrinsic Josephson junctions in Bi$_{2}$Sr$_{2}$Ca$_{2}$Cu$_{3}$O$_{10+\delta }$

Terahertz radiation in the 0.3--10 THz frequency range is a technologically attractive form of electromagnetic radiation, because it has applications in numerous fields. Terahertz generation from stacks of intrinsic Josephson junctions fabricated from Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ (Bi-2212) has become a major focus of both experimental and theoretical research [U. Welp \textit{et al.}, Nat. Photonics \textbf{7}, 702 (2013)]. Here, we observe continuous terahertz emission from a stack of intrinsic Josephson junctions made of Bi$_{2}$Sr$_{2}$Ca$_{2}$Cu$_{3}$O$_{10+\delta }$ (Bi-2223). We investigate how triple CuO$_{2}$ planes affect the c-axis current--voltage and emission characteristics. The terahertz emission spectra are measured by Fourier-transform infrared spectroscopy.