We observe continuous terahertz-wave emission from a stack of intrinsic Josephson junctions made of slightly Pb-doped Bi 2 Sr 2 CaCu 2 O 8 d + . We investigate how Pb doping affects the c-axis current-voltage and emission characteristics. The terahertz emission spectra are measured by Fourier-transform infrared spectroscopy and reveal that the emission frequency is remarkably increased by Pb doping, an effect that we attribute to cavity resonance.

We present an effective engineering technique for compactly packaging high-T c superconducting continuous-wave terahertz source modules. A terahertzemitting device, which consists of stacks of intrinsic Josephson junctions in single crystalline Bi 2 Sr 2 CaCu 2 O 8+δ , bias electrodes, a collimating lens, and other components, is packaged into a single finger-sized assembly. The rigid and stable structure used for the packaging guarantees physical and chemical stability with good thermal contact, and provides reproducible characteristics with a high yield rate. The coherent terahertz waves can be emitted from the back side of the base crystal without significant screening. The intuitive results obtained from the numerical simulation are consistent with the observed thermal properties. The modules are easy to use, and thus intended for all users unfamiliar with superconducting electronic devices.

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