Emitted Phonon Spectrum and Its Influence on the Detected Signal in Superconducting Sn Diodes

We observed experimentally that the detected signal-vs-generator current deviates from linearity. The deviation has a shape similar to that of a Lorentzian. Preliminary arguments lead us to the conclusion that if the maximum deviation occurs at a generator voltage Vₘ the emitted recombination peak should tend to a width given by Vₘ-2Δ. By calculating the spectrum of phonons emitted at a given generator voltage and hence the detector response signal, we have shown that the above prediction is essentially correct. We also give a brief discussion on the behavior of a superconductor when used as a phonon frequency convertor.