Fig. 5.

Characterization of a two-capillary filter. a FEM simulations and b experimental data for two 1 mm outer diameter glass capillaries separated by a 1 mm square metallic rod spacer where both capillaries contain a liquid metal plug in the beam path. In this case, there are multiple resonant features. Two narrow resonant peaks can be seen at 116 GHz and 130 GHz in the signals emerging from Port 3 (red curves), while a resonant peak is observed at 123 GHz emerging from Port 2 (blue curves). c The ratio of Port 3 to Port 2 reveals an isolation ratio of nearly +40 dB at the two outer resonances, and nearly –40 dB at the middle one