Presentation Information
[16a-PA1-10]Microscopic Theory of Linear and Nonlinear Losses in Millimeter-Wave and Terahertz Superconducting Waveguides
〇Takayuki Kubo1,2 (1.KEK, 2.Sokendai)
Keywords:
superconductivity,waveguide,terahertz
We evaluate the attenuation constant (alpha) of the fundamental mode in rectangular superconducting waveguides from the millimeter-wave to terahertz bands by linking standard waveguide theory with the superconducting surface resistance derived from a microscopic theory. The formulation applies to an arbitrary mean free path (mfp): at low frequencies the loss is minimized around mfp ~ xi, while near the gap frequency cleaner samples (mfp>xi) yield lower loss. For NbN, we obtain alpha<0.001 dB/cm at 1 THz and T/Tc=0.25 for mfp=3*xi. We also point out that nonlinear surface resistance becomes important under strong electromagnetic fields.