Time delay signature elimination of chaos in a semiconductor laser by dispersive feedback from a chirped FBG

TL;DR

This paper demonstrates experimentally and numerically that dispersive feedback from a chirped fiber Bragg grating significantly reduces or eliminates the time delay signature in a semiconductor laser, improving chaos control.

Contribution

It introduces the use of dispersive feedback from a chirped FBG to suppress TDS in semiconductor lasers, showing advantages over mirror and uniform FBG feedback.

Findings

TDS decreased by 90% with dispersive feedback

TDS evolution differs from uniform FBG feedback, never rising again

Dispersive feedback does not require amplification or filtering

Abstract

Time delay signature (TDS) of a semiconductor laser subject to dispersive optical feedback from a chirped fiber Bragg grating (CFBG) is investigated experimentally and numerically. Different from mirror, CFBG provides additional frequency-dependent delay caused by dispersion, and thus induces external-cavity modes with irregular mode separation rather than a fixed separation induced by mirror feedback. Compared with mirror feedback, the CFBG feedback can greatly depress and even eliminate the TDS, although it leads to a similar quasi-period route to chaos with increases of feedback. In experiments, by using a CFBG with dispersion of 2000ps/nm, the TDS is decreased by 90% to about 0.04 compared with mirror feedback. Furthermore, both numerical and experimental results show that the TDS evolution is quite different: the TDS decreases more quickly down to a lower plateau (even background noise level of autocorrelation function) and never rises again. This evolution tendency is also different from that of FBG feedback, of which the TDS first decreases to a minimal value and then increases again as feedback strength increases. In addition, the CFBG feedback has no filtering effects and does not require amplification for feedback light.