Efficient detection of midinfrared photons by phonon trapping in superconducting nanowires

Phonons not only serve as the fundamental medium underlying superconductivity but also play a critical role in tuning the performance of superconducting nanowires. Here, we present an efficient approach for detecting midinfrared single photons by leveraging enhanced phonon trapping in superconducting nanowires, which arises from intrinsic acoustic mismatch. In the experiment, the nanowires are patterned on nitrogen-doped amorphous tungsten films, which consist of disordered heavy atoms and weakly doped light atoms. This unique structural composition enables the films to exhibit a phonon group velocity that is significantly lower than that of the silicon substrate. The current-voltage characteristics reveal an ultrahigh ratio of the superconducting switching current to retrapping current ( ∼ 22 ), which is more than three times higher than that of conventional niobium nitride nanowires. We attribute the increased ratio to phonon trapping facilitated by strong intrinsic acoustic mismatch. Furthermore, the fabricated detector achieves saturated internal detection efficiencies across a wavelength range 1.75–6 µm. This work provides a facile strategy for improving the sensitivity of midinfrared single-photon detectors through phonon engineering.