Fig. 1. Experimental setup. DM Laser, discrete-mode laser; OC, optical circulator; FC, fiber coupler; EDFA, erbium-doped fiber amplifier; PC, polarization controller; VA, variable optical attenuator; PM, power meter; PD, photodetector; ESA, electrical spectrum analyzer; OSC, oscilloscope.

Fig. 2. Time series and power spectra of the ECF DM-SL output intensity when bias current is 40 mA, where the feedback ratio ξf is 0.045 (row 1), 0.090 (row 2), and 0.300 (row 3). The gray lines in the power spectra denote the noise floor.

Fig. 3. (a) Time series, (b) power spectra, and (c) phase portraits of the output of ECF DM-SL when I=40  mA, where ξf is 0.048 (row 1), 0.052 (row 2), 0.059 (row 3), and 0.063 (row 4). The insets of the first column show the detail temporal waveforms in a 3 ns time span.

Fig. 4. Duty cycle of the periodic oscillation as a function of ξf when I=40  mA.

Fig. 5. (a) Time series, (b) power spectra, and (c) phase portraits for the output of the DM-SL when I=70  mA, where the feedback ratio ξf is 0.158 (row 1), 0.186 (row 2), and 0.204 (row 3). The insets of the first column show the detail temporal waveforms within 3 ns time span.

Fig. 6. Mapping of dynamical states of the ECF DM-SL in the parameter space of ξf and I.

Fig. 7. (a) Time series, (b) power spectra, and (c) phase portraits for the output of the DM-SL when τ=20  ns, where the J/Jth=3 and the feedback strength κ is 4.2  ns−1 (row 1) and 5.0  ns−1 (row 2). The insets of the first column show the detail temporal waveforms within a 3 ns time span.

Fig. 8. Duty cycle of the periodic oscillation as functions of κ when J/Jth=3 and τext=20  ns.

Fig. 9. (a) Time series, (b) power spectra, and (c) phase portraits for the output of the DM-SL when τ=20  ns, where the J/Jth=6, κ=7.9  ns−1 (row 1) and κ=9.3  ns−1 (row 2). The insets of the first column show the detail temporal waveforms within a 3 ns time span.

Fig. 10. Dynamical state maps of the ECF DM-SL in the parameter space of normalized bias current and feedback strength when τext=10  ns (left column) and τext=20  ns (right column).