Suppression of time delay signatures of chaotic output in a semiconductor laser with double optical feedback

Abstract

We experimentally and numerically demonstrate the time delay (TD) signature suppression of chaotic output in a double optical feedback semiconductor laser (DOF-SL) system. Two types of TD signature suppression are demonstrated by adjusting the lengths and the feedback power ratios of the two external cavities. One can significantly eliminate all TD signatures of the DOF-SL system and the corresponding power spectrum distribution becomes quite smooth and flat, the other suppresses one of two TD signatures and remains another one.

Method to identify time delay of chaotic semiconductor laser with optical feedback

“…6(b), which is consistent with the report in Ref. [11]. However, two peaks are apparent in the IFFT curve from the RF spectrum ( Fig.…”

“…The autocorrelation curve (Fig. 8(b)) shows that the ACF can only distinguish one time delay (i.e., τ cav2 ), which is consistent with the results obtained by Wu et al [11] . However, our method can identify both time delays simultaneously, as shown in Fig.…”

“…These results reveal that the second scenario in Ref. [11] is also not a sufficient condition for security.…”

“…Typical scenarios are to generate high-dimensional chaos [6] , to modulate the delay time [7,8] , and to use multiple feedback [9,10] . Recently, Wu et al experimentally showed that the TD signatures can be suppressed in two limits when double external cavities are used; one is that the two external cavities have roughly equal lengths, and the other is that one cavity length is approximately half of the other [11] . Rontani et al proposed that TD signature identification would be impossible when the TD is close to the relaxation period of the laser operating with weak feedback [12] .…”

Physical Random Number Generations and Photonic Integrated Circuits for Chaotic Generators

“…For the suppression and elimination of time signatures in chaotic semiconductor lasers, several methods have been proposed. For examples, double optical feedback in semiconductor lasers and the generation of chaos by mutually coupled semiconductor lasers were proposed and chaotic signatures were greatly suppressed or even completely eliminated (Wu et al 2009(Wu et al , 2011). …”