Fig. 1. Second-order photon cross-correlation of the mixed light (50∶50 ratio of chaotic laser to coherent laser) versus τ and τ_c when l=15 m and τ_c=τ_φ. (a) m=min(|τ|,|l/c|); (b) m=|l/c|

Fig. 2. Second-order photon cross-correlation results of chaotic laser versus τ and τ_c when l=15 m

Fig. 3. Second-order photon cross-correlation results of coherent laser versus τ and τ_c when l=100 m

Fig. 4. Relationship between second-order photon cross-correlation and proportion P of chaotic laser

Fig. 5. Second-order photon cross-correlation results of mixed laser. (a) τ_c<τ_φ; (b) τ_c=τ_φ; (c) τ_c>τ_φ

Fig. 6. Schematic of experimental setup for measuring second-order photon cross-correlation of chaotic laser and distinguishing between different chaotic states

Fig. 7. Experimental time series and frequency spectrum under different feedback strengths. (a) η=2.5% time series; (b) η=2.5% frequency spectrum; (c) η=18% time series; (d) η=18% frequency spectrum

Fig. 8. Experimental results of second-order photon cross-correlations. (a) Coherent light; (b) mixed light; (c) chaotic light