Impact of α-factor, combined optical phase and gain saturation on the onset of chaos of short external cavity semiconductor lasers

Abstract

Influences of line-width enhancement factor (α-Factor), combined optical phase (COP), and gain saturation (GS) on the onset of chaos (route to chaos (RTC)) of the short external cavity (EC) semiconductor lasers (LDs) are numerically investigated. The bifurcation diagrams (BDs), output photon number time variations, corresponding phase portraits, and fast Fourier transforms (FFT) are presented to examine the RTC of the laser in terms of GS, COP, and α-Factor. Calculated results displayed that variation of the α-Factor leads to RTC considerable modifications and these changes are positive by including the GS. The COP variation moves the optical feedback (OFB) intensity to higher values and causes fluctuations in the RTC of the LD with and without including the GS. The LD RTC is specified for four separate regions, oscillations with one frequency (PO), oscillations with two frequencies (PD), oscillations with three frequencies (3P), and oscillations with four frequencies (4P), in terms of GS, COP, and α-Factor. As the LD operation state moves from continuous wave (CW) to PO, PD, or chaos operation state the OFB intensity decreases / increases through α-Factor / GS increasing and fluctuates with increasing the COP within one period (0–2π). The results presented here can be useful in designing stable LD and directing chirp in integrated devices through COP and α-Factor changing.