Concealment of time delay signature of chaotic output in a slave semiconductor laser with chaos laser injection

• The time delay (TD) signature generally exists for the chaotic semiconductor laser with optical feedback, which will certainly go against its application in secure communication.
• The TD signature for both intensity and phase chaos can be concealed through an improved chaotic laser system, which has a slave semiconductor laser injected by a master SL with double optical feedback.
• The more favourable result is that the bandwidth of chaotic laser output can be improved by choosing the optimal detuning frequency in our improved chaotic laser system.

An improved chaotic laser system, which has a slave semiconductor laser (SL) injected by a master SL with double optical feedback (DOF), is proposed, so that the time delay (TD) signature can be successfully concealed from both intensity and phase chaos via choosing appropriate parameters. The TD signature is investigated by employing autocorrelation function (ACF) and mutual information (MI) function. Through analyzing the influence on TD signature in the region of injection current and injection strength for the slave SL, we find that, for both intensity chaos and phase chaos, the TD signature can be easily concealed under weak injection strength. When the injection strength is strong, we can not only successfully conceal TD signature, but also improve the bandwidth of chaotic laser output by choosing the optimal detuning frequency.