Fig. 1. Experimental systems of speckle suppression using chaotic lasers. (a) Experimental setup diagram; (b) experimental setup of chaos generation with optical feedback; (c) experimental setup of chaos generation by electrical chaotic signal modulation

Fig. 2. Time series and speckle patterns of the laser diode with and without optical feedback disturbance when I=1.9I_th. (a1)(b1) Without optical feedback disturbance; (a2)(b2) feedback strength is -2.1 dB

Fig. 3. Influence of feedback strength and bias current on speckle contrast in a chaotic system with optical feedback. (a) Influence of feedback strength on speckle contrast when bias current is 1.9I_th; (b) influence of bias current on speckle contrast when feedback strength is -2.1 dB

Fig. 4. Time series and speckle patterns of laser diode with and without electrical chaotic signal modulation when I=1.9I_th. (a1)(b1) Without chaotic signal modulation; (a2)(b2) modulation amplitude of chaotic signal is 4.8 V

Fig. 5. Influence of modulation amplitude and bias current on speckle contrast in a chaotic system using electrical chaotic signal modulation. (a) Influence of modulation amplitude on speckle contrast when bias current of the laser diode is 1.9I_th; (b) influence of bias current on the speckle contrast when modulation amplitude of laser diode is 4.8 V