Simultaneous Coherent Detection With Baseband Enhancement in Chaotic Random Bit Generation by an Optically Injected Laser

Optical injection into a semiconductor laser invokes chaos that is coherently detected without direct detection for fast random bit generation (RBG). Originating from the injection without any feedback, the chaos contains no undesirable time-delay signature. Although the injection dynamics only supports a low dimensionality of three, simultaneous coherent detection uses the two dimensions of intensity
$I$
and phase
$\varphi $
in yielding two signals
$I_{\mathrm{H}}$
and
$I_{\mathrm{B}}$
, which are from heterodyning and balanced delayed homodyning, respectively. Compared to
$I$
from direct detection, the two coherently detected signals
$I_{\mathrm{H}}$
and
$I_{\mathrm{B}}$
are baseband-enhanced for effectively utilizing the low-frequency responses of the detectors. Experimentally, on a laser with a relaxation resonance of 5.2 GHz,
$I_{\mathrm{H}}$
and
$I_{\mathrm{B}}$
are baseband-enhanced by 8 dB and 12 dB, respectively. Through a basic postprocessing by discarding bits, they are digitized for RBG with an output bit rate reaching 280 Gbps. Through an extensive postprocessing by involving pseudo-random contributions, a boosted output bit rate of 1.28 Tbps is possible even when the detection bandwidth is reduced to 3 GHz. Both postprocessings satisfy a set of standardized randomness tests from the National Institute of Standards and Technology. Based on the simultaneous coherent detection, the potential of baseband enhancement is illustrated for the low-dimensional dynamics from injection.