Fig. 4: Modulation performances of the plasmonic metafiber EOM.

a Experimental setups for direct current (DC) and alternative current (AC) modulation characterizations, which consist of a light source, a metafiber EOM, a signal generator with a voltage amplifier and an optical detector. Depending on DC or AC modulation tests, the light source could be selected as either a supercontinuum laser (SCL) or a tunable telecoms laser (TL), the signal generator uses either static bias voltages or radio frequency (RF) bit signals, and the optical detector is either an optical spectrum analyzer (OSA) or a fast oscilloscope with photodetector (OPD). b DC modulation performance of the plasmonic metafiber EOM. The reflection spectrum of plasmonic metafiber undergoes a redshift when the DC bias voltage changes from −100 V (green line) to +100 V (red line). The inset shows a modulation depth of 11% at the wavelength of 1287 nm. c AC modulation performances of plasmonic metafiber EOM at different driving frequencies. Top row shows the temporal responses of an oscilloscope under a constant bias voltage of ±1 V; the bottom row shows the temporal responses of an oscilloscope with nearly the same amplitude of output signals