We demonstrate single-photon counting at 1550 nm with titanium-nitride (TiN) microwave kinetic inductance detectors. Energy resolution of 0.4 eV and arrival-time resolution of 1.2 microseconds are achieved. 0-, 1-, 2-photon events are resolved and shown to follow Poisson statistics. We find that the temperature-dependent frequency shift deviates from the Mattis-Bardeen theory, and the dissipation response shows a shorter decay time than the frequency response at low temperatures. We suggest that the observed anomalous electrodynamics may be related to quasiparticle traps or subgap states in the disordered TiN films. Finally, the electron density-of-states is derived from the pulse response.
@article{arxiv.1208.0871,
title = {A titanium-nitride near-infrared kinetic inductance photon-counting detector and its anomalous electrodynamics},
author = {J. Gao and M. R. Visser and M. O. Sandberg and F. C. S. da Silva and S. W. Nam and D. P. Pappas and K. D. Irwin and D. S. Wisbey and E. Langman and S. R. Meeker and B. A. Mazin and H. G. Leduc and J. Zmuidzinas},
journal= {arXiv preprint arXiv:1208.0871},
year = {2015}
}