Fig. 1.

A reconfigurable T-junction power switch. A T-junction waveguide with a mechanically repositionable septum can be used as a variable-ratio power splitter. a, b We incorporate a pair of liquid metal channels into the two output arms of the T. The metal plug can be moved in these channels using a DC voltage. This causes the side wall of the T-junction waveguide section to be either metal (when the metal plug is inserted) or a highly absorbing liquid electrolyte (when the metal plug is withdrawn). Here, the signal emerging to the right (Port 3) is present when the right-hand channel contains metal (a), and absent when the metal is withdrawn, leaving only electrolyte (b). c, d Numerical simulations using COMSOL, showing the change in the signal propagating in Port 3 when the liquid metal plug is present (c) and when it is replaced with absorbing electrolyte (d) on the right side. The channel on the left side (Port 2) has liquid metal in both cases. e The measured spectrum of the power ratio (metal plug inserted vs. withdrawn) for the Port 2 output of the T-junction, for the case when Port 3 has liquid metal (red) and electrolyte (blue). A broad spectral region is observed for which the on–off ratio exceeds 20 dB. The two curves are very similar, indicating that the output of Port 2 is unaffected by the state of Port 3. The black solid curve shows the predicted ratio from COMSOL simulations. f Characterization of this switch using modulated data at 1 Gb/s, at 200 GHz carrier frequency. The bit error rate for the signal from Port 2 reaches error-free (10⁻⁹) performance when the metal plug is inserted, for both states of the channel in Port 3. The small difference between these two curves is an indication of a small degree of cross-talk due to a back reflection from the liquid metal plug on the Port 3 side. When the metal plug is removed from Port 2, the signal from that port is much too small to measure a BER