Fig. 1. Chaotic laser generation methods. (a) Optical feedback; (b) optical injection; (c) optoelectronic feedback

Fig. 2. Generation of broadband chaotic lasers by active optical feedback loop based on HNLF^[42]. (a) Experimental setup; (b) power spectra

Fig. 3. Generation of flat broadband chaotic lasers using asymmetric dual-path optical feedback ^[43]. (a) Experimental setup; (b) power spectra

Fig. 4. Generation of flat broadband chaotic laser based on mutual injection method ^[56]. (a) Experimental setup; (b) power spectra

Fig. 5. Generation of chaotic lasers with broadband and TDS suppression based on the asymmetric mutual injection method ^[57]. (a) Experimental setup; (b) chaotic characteristics, including power spectra, optical spectra, time series, and ACF

Fig. 6. Relationship between the synchronisation coefficients and the output characteristics of the two DFB lasers. (a) Map of the synchronisation coefficients for the bandwidth of two DFB lasers; (b) map of the synchronisation coefficients for the TDS of two DFB lasers

Fig. 7. Three-segment photonic integrated chip based on optical feedback structure ^[67]. (a) Experimental setup; (b) chaotic characteristics, including optical spectrum, power spectrum, time series, and ACF

Fig. 8. Wavelength-tunable monolithic integrated chaotic semiconductor laser chip ^[68]. (a) Experimental setup; (b) chaotic characteristics, including optical spectrum, time series, power spectrum, and phase diagram; (c) wavelength-tunable characteristics of chaotic laser, including optical spectra, power spectra, side mode suppression ratio and linewidth, and standard bandwidth

Fig. 9. Monolithic integrated chaotic semiconductor laser based on stochastic feedback and mutual injection ^[73]. (a) Experimental setup; (b) chaotic characteristics, including time series, power spectrum, ACF, and phase diagram; (c) simplified model diagram of the random grating in a passive optical waveguide

Fig. 10. Generation of chaotic laser by a curved-edge hexagonal microcavity laser based on internal mode interactions ^[74]. (a) Experimental setup; (b) characteristics of chaos, including time series, power spectrum, ACF, correlation integral curves, correlation dimension, and K-entropy