We re-examined the angular dependence of the radiation from the intrinsic Josephson junctions in rectangularmesas of Bi2Sr2CaCu2O8 + δ, in order to determine if the cavity mode part of the radiation arises from waves across the widthw or along the length of the mesas, associated with ‘hot spots’ (Wang et al 2010 Phys. Rev. Lett. 105 057002).We derived analytical forms for the angular dependence expected in both cases for ageneral cavity mode in which the width of the mesa corresponds to an integer multiple ofone-half the wavelength of the radiation. Assuming the coherent radiation from the acJosephson current source and the cavity magnetic surface current density source combineincoherently, fits to the data of Kadowaki et al (2010 J. Phys. Soc. Japan 79 023703) on amesa with mean for both wave directions using two models for the incoherent combination were made,which correspond to standing and traveling waves, respectively. The results suggest thatthe combined output from the uniform ac Josephson current source plus a cavity waveforming along the rectangle length is equally probable as that of the combined output fromthe uniform ac Josephson current plus a cavity wave across the width. However, for mesasin which is integral, where n is theindex of the rectangular TMzn, 0 mode, it is shown that standing cavity mode waves along the length of the mesa do not radiate in thexz plane perpendicular to the length of the mesa, suggesting experiments on such mesas couldhelp to resolve the question.
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