Superconducting Microstrip Losses at Microwave and Sub-millimeter wavelengths

Abstract

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{é}rot resonators (FPR) operating around $350$GHz. 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 $\tan \delta =3.7\pm 0.5\times 10^{-5}$ at $6$GHz and $\tan \delta =2.1\pm 0.1\times 10^{-4}$ at $350$GHz. 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.

8 pages, 3 figures

References in corpus (2)

• Generalized Tunneling Model for TLS in amorphous materials and its predictions for their dephasing and the noise in superconducting microresonators
• Thin film dielectric microstrip kinetic inductance detectors