Entropy rate of chaos in an optically injected semiconductor laser for physical random number generation

We evaluate the (epsilon, tau) entropy of chaotic laser outputs generated by an optically injected semiconductor laser for physical random number generation. The vertical resolution epsilon and sampling time tau are numerically optimized by comparing the (epsilon, tau) entropy with the Kolmogorov-Sinai entropy, which is estimated from the Lyapunov exponents using linearized model equations. We then investigate the dependence of the (epsilon, tau) entropy on the optical injection strength of the laser system. In addition, we evaluate the (epsilon, tau) entropy from the experimentally obtained chaotic temporal waveforms in an optically injected semiconductor laser. Random bits with an entropy close to one bit per sampling point are extracted to satisfy the conditions of physical random number generation. We find that the extraction of the third-most significant bit from eight-bit experimental chaotic data results in an entropy of one bit per sample for certified physical random number generation. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement