Figure 4. Influence of periodic forcing in the organization of the symbolic patterns.

(a), Probabilities computed from the experimental data. The DC value of laser pump current is 39 mA and the modulation amplitude is increased from 0 mV to 78 mV (0% to 4% of the DC current, other experimental parameters are as described in Methods). The two word clusters are clearly seen, which are the same as without modulation. A crossover in the word hierarchy can also be observed at about 1.8%. (b), Probabilities computed from the modified circle map, when varying the parameter K with constant noise strength. Here again, the hierarchical and clustered structure of the probabilities is in good qualitative agreement with that in the experimental data. The parameters are ρ = −0.23, α_c = 0.2 and β_c = 0.002. (c), Probabilities computed with the modified circle map considering a noise strength that decreases with the modulation amplitude. For weak modulation the agreement with the experimental probabilities is further improved.