Fig. 1. (a) Epitaxial wafer structure of the DFB-SA, (b) schematic of the fabricated DFB-SA chip, and (c) sample of the fabricated DFB-SA chip.

Fig. 2. (a) Experimental setup for a photonic spiking neuron based on the DFB-SA; (b) PI curves of the DFB-SA for VSA=0  V and VSA=−0.4 V; (c) optical spectra of the free-running DFB-SA for VSA=0  V, IG=99  mA and VSA=−0.4  V, IG=120  mA.

Fig. 3. (a1)–(a3) Time series of period spike outputs; (b1)–(b3) the corresponding power spectra of the DFB-SA for different gain currents with VSA=−0.4  V, IG=115  mA, IG=120  mA, and IG=130  mA.

Fig. 4. Spike frequency as a function of the gain current for different cases of VSA.

Fig. 5. Excitability threshold property of DFB-SA subject to external perturbations. (a) The external stimulus; (b) the response output, the inset represents the enlargement of a single spike; (c) temporal maps plotting the response of the DFB-SA neuron to the arrival of 100 consecutive external stimuli with VSA=−0.4  V and IG=99.2  mA. The wavelength of the injected laser is 1548.61 nm.

Fig. 6. Temporal integration behavior of the DFB-SA spiking neuron: (a) the external stimulus with pulse pairs having different ISIs; (b) the response with VSA=−0.4  V and IG=94  mA. The ISI for seven pulse pairs is, respectively, 0.40 ns, 0.48 ns, 0.64 ns, 0.66 ns, 0.80 ns, 0.86 ns, and 1.0 ns.

Fig. 7. Refractory period behavior of the DFB-SA spiking neuron: (a) external stimulus with pulse pairs having different interspike interval; (b)–(f) the response under different conditions of the gain current. The gain current is, respectively, (b) 98.7 mA, (c) 104.4 mA, (d) 105.1 mA, (e) 111.0 mA, and (f) 112.1 mA. The ISI for seven pulse pairs is, respectively, 0.48 ns, 0.58 ns, 0.72 ns, 0.88 ns, 1.0 ns, 1.16 ns, and 1.24 ns.

Fig. 8. Schematic of the DFB-SA subject to external optical injection.

Fig. 9. Numerical results of time series (left column) and power spectra (right column) of the self-pulsation output of the DFB-SA. (a) IG=45  mA, (b) IG=48  mA, and (c) IG=51  mA and ISA=0  mA.

Fig. 10. Numerical results of the neuronlike response: (a) represents the stimuli; (b) represents the response with IG=41.7  mA and ISA=0  mA.

Fig. 11. (a) The schematic of an ANN-to-SNN conversion using the photonics spiking neuron based on DFB-SA. (b) The activation function; the solid line is the curve of the measured data, and the dashed line is the corresponding polynomial fitting of the optical activation function. (c) The training and test accuracy for the MNIST dataset and (d) the confusion matrix of the inference task.

Table 1. Basic Parameters Used in This Paper [33,34]