We present a lab-on-chip experiment to accurately measure losses of superconducting microstrip lines at microwave and sub-mm wavelengths. The microstrips are fabricated from NbTiN, which is deposited using reactive magnetron sputtering, and amorphous silicon which is deposited using plasma-enhanced chemical vapor deposition (PECVD). Sub-mm wave losses are measured using on-chip Fabry-P{\'e}rot resonators (FPR) operating around 350GHz. Microwave losses are measured using shunted half-wave resonators with an identical geometry and fabricated on the same chip. We measure a loss tangent of the amorphous silicon at single-photon energies of tanδ=3.7±0.5×10−5 at 6GHz and tanδ=2.1±0.1×10−4 at 350GHz. These results represent very low losses for deposited dielectrics, but the sub-mm wave losses are significantly higher than the microwave losses, which cannot be understood using the standard two-level system loss model.
@article{arxiv.2108.11095,
title = {Superconducting Microstrip Losses at Microwave and Sub-millimeter wavelengths},
author = {S. Hähnle and K. Kouwenhoven and B. Buijtendorp and A. Endo and K. Karatsu and D. J. Thoen and V. Murugesan and J. J. A. Baselmans},
journal= {arXiv preprint arXiv:2108.11095},
year = {2021}
}