Figure 1

Random-bit generation scheme and device structures. (a) Schematic diagram of random-bit generation. ADC denotes the analog-digital converter. (b) Schematic of the random signal generator module consisting of two chaos laser chips. Chip resistors are used for impedance matching and current is injected to the distributed feedback (DFB) laser and semiconductor optical amplifier (SOA) contacts of the chaos laser chips via bonding pads (wires not shown here). Electrical signal is output from the photodiodes (PDs) in the chaos laser chips via microstriplines to high-frequency connectors. (c) Photo of a random signal generator module. (d) Optical image showing the monolithically integrated optical components. A small section of the 10-mm-long passive waveguide for optical feedback can be seen. DFB laser, semiconductor distributed feedback laser; SOA1 and SOA2, semiconductor optical amplifiers, The width of the waveguide is 2 $\mu$m. The lengths of the PD, DFB laser, SOA1, SOA2, and passive waveguide are, respectively, 50 $\mu$m, 300 $\mu$m, 200 $\mu$m, 100 $\mu$m, and 10 mm.Reuse & Permissions

Figure 2

Random-bit generation using the random signal generator module. Temporal wave forms of the two module outputs and corresponding binary digitized signals (a) 00111111010$\dots$ and (b) 0110010110$\dots$. Dots mark points sampled with 2.08 GHz sampling rate. The threshold value for the ADC is zero, shown as a solid line. The random bit sequence output after the XOR operation is 01011010111$\dots$.Reuse & Permissions

Figure 3

The “vanishing time” of the autocorrelation functions. The colors indicate the time (ns) required for the exponentially decaying envelope of the autocorrelation function to becomes less than 0.1.Reuse & Permissions

Figure 4

Numerical results on the convergence of the density and autocorrelation function. (a) Difference between the evolving time density and the invariant density. Inset: Any smooth initial density (the green curve) converges to the invariant density (the red curve). (b) The autocorrelation function.Reuse & Permissions

Figure 5

Radio-frequency spectra and autocorrelation functions for $I_{\mathrm{SOA}1}=$ (a), (b) 2 mA; (c), (d) 6 mA; and (e), (f) 10 mA.Reuse & Permissions