Mesa structures of Bi2Sr2CaCu2O8 + δ (Bi-2212) high-temperature superconductor represent stacks of intrinsic Josephson junctions. Josephson junctions allow direct conversion of DC voltage into high-frequency electromagnetic waves with tunable frequency f = (2e/h) V (= 0.48359 THz/mV). Thus, superconductors can provide an alternative technology for creation of compact THz sources. It has long been anticipated that small Bi-2212 mesas may have many benefits as THz oscillators: (i) Edge effects and capacitive coupling persuade in-phase synchronization of junctions, needed for superradiance; (ii) Selfheating is reduced proportional to the mesa size, which allows operation at high voltages and frequencies; (iii) The frequency and the quality factor Q of the primary geometrical resonance (cavity mode) increase inversely proportional to the mesa size. Fiske steps with Q > 100 were reported for μm- size Bi-2212 mesas. This should strongly boost the emission efficiency because high-Q resonances enhance the emission power Q2 and decrease the line-width 1/Q. (iv) Small mesas can be made free from defects and with identical junctions, simplifying their synchronization. Here we demonstrate that small-but-high Bi-2212 mesas can be used as high-frequency electromagnetic wave generators in a record high frequency range up to 11 THz [1]. We argue that a threshold number of junctions N>100 is needed for coherent superradiant emission from the mesas. We demonstrate several ways of detection of radiation: using a nearby mesa on the same crystal as a switching current detector, or an external bolometer. The Figure represents generationdetection experiment in the 1-11 Thz range with inbuilt detector. Two mesas with different sizes and detector configurations are presented. a, d I–V characteristics of generator mesas. b, e Measured detector responses as a function of the generator voltage per junction. c, f Emission spectra: detector response vs. Josephson frequency for the falling parts of the generator I–V curves. Vertical bars on top of c, f mark expected frequencies of strong emitting in-phase geometrical resonances in mesa with sizes Lx*Ly corresponding to those generators. The estimated maximum emission power ~1μW indicates an encouraging DC to AC conversion efficiency.