a Architecture of the implementation. The graphene heterostructure is incorporated on one side of the resonator. Optical micrographs show that we can drive the resonator by using electric probes and green scattering is excited by the gain media (upper panel). Here, the bar is 60 μm (bottom panel). b Transmission and reflection of the resonator. c Laser evolution (VSD = 16 V). By increasing the pump power, the laser operation travels from CW to multimode and then to locking. The laser threshold is ≈60 mW and the mode-locking threshold is ≈450 mW. Curves i to v plot the measured spectra of the laser states. d Characterization of the mode-locked state, from left to right: magnified optical spectrum, the first-order beat note in RF, and the frequency-resolved autocorrelation map
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