Numerical analysis of optical feedback phenomenon and intensity noise of fibre‐grating semiconductor lasers

Abstract

SUMMARYThis paper demonstrates numerical analysis of the dynamics and intensity noise of fiber grating semiconductor lasers (FGSLs). The induced phenomenon of strong optical feedback (OFB) is analyzed. The simulations are based on an improved time-delay rate equations model of a single-mode laser that takes into account the multiple round trips of the lasing field in the fiber cavity. The analyses are performed in terms of the temporal trajectory of the laser intensity, bifurcation diagram and relative intensity noise (RIN). We explore influence of the fiber-cavity length on the dynamics and RIN. The results show that when the fiber-cavity is short, the regime of strong OFB is characterized by either continuous-wave (CW) operation or periodic pulsation. The pulsation frequency is locked at the frequency separation of either the compound-cavity modes or the external fiber-cavity modes. The corresponding RIN level is close to or higher than the level of the solitary laser depending on pulse symmetry. When the fiber cavity is long, the laser exhibits unstable dynamics over wider range of OFB. Moreover, the strong-OFB pulsation becomes beating quasi-periodic at the relaxation oscillation frequency and the fiber-cavity mode-separation frequency.

Numerical modeling of the output and operations of semiconductor lasers subject to strong optical feedback and its dependence on the linewidth‐enhancement factor

“…In the application of the FGSL as a pumping source to optical fiber amplifiers, it is important to examine influence of the external OFB on the power P g emitted from the FG and the power P b emitted from the HRC at the back facet. These powers are calculated based on a traveling wave model of the lasing field in the laser and external cavities as 7 where X is another OFB function describing transmission of the lasing field in the external fiber cavity, and is given by 11: …”

“…In 7, 8, the authors took part in developing a versatile time‐delay model to analyze the operation of semiconductor lasers under an arbitrary amount of OFB ranging from very weak to very strong. The model was successfully employed to investigate operation characteristics and noise of FGSLs 10, 11.…”

Numerical modeling of the route‐to‐chaos of semiconductor lasers under optical feedback and its dependence on the external‐cavity length

“…In this paper, we apply the improved time-delay model in [11] to analyze the OFB phenomenon in semiconductor lasers. The model is schematically illustrated in Figure 1.…”

“…Therefore, OFB is one of the most studied problems in laser dynamics, but yet it has not been fully understood because of its complexity, nonlinearity and the large number of included parameters. The route-to-chaos is one of the interesting nonlinear phenomena associated with OFB; it may include dynamics with period-doubling (PD), sub-harmonics (SH) or quasi-periodicity [6][7][8][9][10][11]. PD is observed in the limit of short-external cavity [7,[9][10][11]; it follows a region of periodic oscillation and is characterized by the periodic oscillation frequency and its half harmonic.…”

“…Kao et al [9] predicted that this frequency should correspond to Hopf-bifurcation point (the onset of periodic oscillation). The quasi-periodic (QP) route-to-chaos dominates the long-external-cavity dynamics and is a manifest of competition between resonances of the laser cavity and the external cavity [1,6,[8][9][10][11]. Kao et al [9] reported that QP is characterized by the Hopfbifurcation frequency with a beaten component of nearly the external-cavity resonance frequency.…”