Dynamics of semiconductor lasers with polarization rotated feedback and its applications for fast random bit generation

Semiconductor lasers are nowadays most prominently used in telecommunications and data communications due to their small dimensions and cost-efficiency. One application of current interest is random bit sequence generation using chaotic semiconductor laser dynamics. Chaotic semiconductor lasers are attractive for this, since they allow for high bit rates in the GBit/s range. At the same time, as analog systems with noise, they avoid the shortcomings of digital systems, representing real random bit sequence generators, rather than pseudo-random bit sequence generators. Most of the recent studies are based on lasers subjected to coherent optical feedback, and require extensive signal processing using logic functions or high-order derivatives to achieve high generation rates. This paper proposes a new experimental scheme of random bit sequence generation based on semiconductor laser dynamics induced by polarization rotated feedback, where the interaction between the TE and TM-mode intensities through the carrier density generates chaotic instabilities. This method relies on rapid decorrelation of the high-frequency chaotic laser dynamics, and thus can produce fast random bits with minimal post-processing.