Dynamics of semiconductor laser diodes with delayed optical feedback and their application for the high-bit-rate generation of random-number sequences
Kim, Byung Chil
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This thesis focuses on the chaotic dynamics of an external cavity semicon-ductor laser (ECSL) and their application for the high-bit-rate generation of random-number sequences. On the one hand, we are interested in experimentally studying fundamental nonlinear dynamics phenomena by using semiconductor laser systems. Considerable and systematic information concerning the dynamical regimes and the bifurcations between them is conveyed by the bifurcation diagram (BD) obtained by fixing all but one parameter and then mapping out the extremal values of a conve-niently measured dynamical variable as the parameter varies. BDs provide a global picture of the dynamical system and it enables systematic investigations of the rich variety of dynamical behavior observed in ECSLs, including laser diode (LD) station-ary dynamics, multistability, intermittency between stable states, and various routes to chaos, in terms of transitions between these types of behavior. We focus on the measurement of intensity time series and the mathematical and numerical analysis of generated (and simulated) time series, extracted random-number sequences, the information-theoretic estimation of bounds on the rate of random-number generation, and the information-theoretic analysis of post-processing techniques. With regard to fundamental properties, we show the statistical nature of chaotic intensity time series from ECSLs and their use for random-number generation. Also, we report the experimental investigation of two different approaches to random bit generation based on the chaotic dynamics of a semiconductor laser with optical feed-back. The first approach is based on computing high-order finite differences of the chaotic laser intensity time series. The second approach is based on pragmatic considerations and could lead to rates of 2.2 Tb/s by extracting 55 bits per sample.