Enhanced complexity of optical chaos in a laser diode with phase-conjugate feedback

Abstract

We demonstrate numerically that a semiconductor laser subjected to phase-conjugate feedback (PCF) can exhibit an enhancement in the complexity of chaos by comparison to conventional optical feedback. Using quantifiers from spectral analysis and information theory, we demonstrate that under similar parametric conditions, PCF exhibits a larger chaotic bandwidth and higher spectral flatness and statistical complexity. These properties are of utmost importance for applications in secure communications and random number generation.

Wideband chaos from a laser diode with phase-conjugate feedback

“…a first rapid linear increase then almost saturation of chaos bandwidth with feedback ratio, contradict earlier theoretical predictions from our group: in Ref. [24] numerical simulations of a PCF laser model found a monotonic linear increase of the chaos bandwidth with the feedback ratio, as is also observed in a conventional optical feedback configuration but with a much faster increase. However, this simulation was performed on a PCF laser model with instantaneous phase-conjugation and therefore did not consider the filtering effect of the phase-conjugate mirror related to its finite penetration depth.…”

Effect of Bias Current on Complexity and Time Delay Signature of Chaos in Semiconductor Laser With Time-Delayed Optical Feedback

“…There are troughs at the feedback round trip time and its subharmonics for all three bias currents. The trough value at the feedback round time is adopted to be used to measure the complexity of chaos [32]. Fig.…”

“…Several techniques have been used to quantify the complexity of chaos, such as Lyapunov exponents [37], [38], strangeness of strange attractors [39] and permutation entropy (PE) [29][30], [32], [40][41]. PE has a few advantages over other techniques, which includes easy implementation, faster computation and being robust to noise.…”

“…The bandwidth and TD signature of chaos have been studied extensively [15]- [28]. Complexity of chaos has also been investigated [29]- [32]. Effect of optical injection strength, frequency detuning and feedback strength on the complexity, bandwidth and TD have been broadly reported.…”

Evaluating entropy rate of laser chaos and shot noise

“…To mimic the frequency-band extractor, the theoretical time series of chaos are mixed with a sinusoidal signal and filtered using a Chebyshev Type-II LPF with a bandwidth of 100 MHz. The PE definition can be found in Refs [20][21][22][23][24][25]. and the embedding dimension d is chosen as 5 inFig.…”