Conceal Time Delay Signature of Chaos in Semiconductor Lasers With Dual-Path Injection

The time delay (TD) signatures of chaotic signals in semiconductor lasers (SLs) with dual-path injection (DPI) are investigated numerically and experimentally based on the autocorrelation function and the permutation entropy function, and are compared with those for chaotic signals in SLs with single-path injection (SPI). Both the intensity and phase chaos are considered. The regions of injection strength and frequency detuning contributing to TD concealment are identified. The optimal selection of injection delays for the DPI case is also suggested. It is found that, for both intensity and phase chaos, the TD signature for the DPI case can be better concealed in wider parameter regions than that for the SPI case, which is highly desirable for security-enhanced chaotic communication systems as well as high-speed random number generators based on chaotic SLs.