Bandwidth and unpredictability properties of semiconductor ring lasers with chaotic optical injection

• We study semiconductor ring lasers with chaotic optical injection.
• We evaluate the bandwidth and unpredictability degree of chaotic signal.
• The enhancement of bandwidth and unpredictability degree can be achieved.
• The results could be valuable for chaos-based communications.
• The results could also be valuable for fast random number generations.

The bandwidth and unpredictability properties of chaotic semiconductor ring lasers (SRLs) are numerically investigated. The SRL is brought to chaotic behaviors by utilizing chaotic optical injection from a master laser with optical feedback. The bandwidth and unpredictability degree of chaotic signal are examined for parameter regions of injection strength and frequency detuning. The chaos unpredictability degree is evaluated quantitatively by permutation entropy (PE). It is shown that, chaos can be obtained in large parameter regions, and simultaneous enhancement of bandwidth and unpredictability degree could be achieved for proper injection parameters. Such results are important for carrying out chaos-based communications and fast random number generations (RNGs).