QuantAlps
An ecosystem for quantum sciences & technologies 

We present a new kind of on-chip surface plasmon polariton (SPP) detector based on kinetic inductance detectors (KIDs). Our device combines a hybrid NbTiN-Al microwave resonators architecture, where aluminum serves not only as a photon absorber but also as a plasmonic material. The characteristics of this new detector are demonstrated by detecting optically excited surface plasmon polaritons (SPPs) at a wavelength of 1.5 µm. Notably, our detector enables direct observation of quasiparticle diffusion in aluminum, providing new insights into non-equilibrium dynamics at the nanoscale. By detecting SPPs from inelastic tunneling in Al/Al₂O₃/Al junctions, this work opens new approaches for probing current fluctuations at optical frequencies.