Abstract
The nonlinear dynamics and frequency locking of semiconductor lasers under repetitive optical pulse injection are studied numerically. Different dynamical states, including pulsation and oscillation states, are found by varying the intensity and the repetition frequency of the injection pulses. Through individual period-doubling routes, the laser enters into chaotic pulsation (CP) states and chaotic oscillation (CO) states, respectively. Moreover, the bandwidths of the chaos states are also investigated. The time series and power spectra of frequency-locked states with di®erent winding numbers, which is the ratio of the oscillation frequency and the repetition frequency of the injection pulses, are shown. Chaotic communication of semiconductor lasers under repetitive optical pulse injection is demonstrated and investigated numerically. The advantages of this chaotic communication system include large bandwidth, robust, and high security compared to the chaotic communication system based on constant optical injection. In this system, the chaotic carrier is generated by injecting repetitive pulses to a semiconductor laser. The message is encoded to the chaotic carrier with additive chaotic modulation (ACM) method, while decoding is realized by synchronizing a receiver laser with a transmitter laser. For a signal-to-noise ratio (SNR) above 30 dB, a bit-error-rate (BER) below the benchmark of 10-9 set by the conventional communication is achieved.