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The nanolaser is composed by two sections for the gain and saturable absorber: a metal screen ensure selective pumping of the gain section with a CW laser beam. By a suitable choice of the parameters (Q-factor, gain vs absorption ratio and pumping rate), the laser operates in different regimes: excitable, pulsing with variable rate (i.e. implements the Leak Integrate and Fire model of the neuron), bistable and CW. Excitability is shown in the figure: panels (c) to (e) relate to the response to a pulsed excitation as a function of its energy (here estimated before the input coupler to the silicon chip) when the pump is set just below the threshold of self-pulsing. Panel (f) shows the spiking probability, estimated as the fraction of traces where spikes are emitted (the event is detected when signal goes above -40 arb.u.). The spiking probability follows the expected trend with the excitation, already observed in VCSELs [6] and agrees very well with our stochastic implementation of the Yamada model of self-pulsing lasers. This result paves the way to electrically pumped, interconnected spiking nanolasers, operating with manageable (0.1 mA) current levels and sub-nanosecond time scales. References [1] B. J. Shastri et al., “Photonics for artificial intelligence and neuromorphic computing,” Nat. Photon. 15, 102 (2021). [2] Y. Shen et al., “Deep learning with coherent nanophotonic circuits,” Nat. Photon. 11, 441 (2017). [3] A. Jha et al., “Reconfigurable all-optical nonlinear activation functions for neuromorphic photonics,” Opt. Lett. 45, 4819 (2020). [4] H.J. W¨unsche et al., ”Excitability of a semiconductor laser by a two-mode homoclinic bifurcation” , Phys. Rev. Lett. 88, 023901 (2001). [5] T. Van Vaerenbergh et al., “Cascadable excitability in microrings,” Opt. Express 20, 20292 (2012). [6] F. Selmi et al., “Relative Refractory Period in an Excitable Semiconductor Laser,” Phys. Rev. Lett. 112 183902 (2014). |
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