Investigation On Polarization Switching And Nonlinear Dynamics Of 1550nm-VCSELs With Optoelectronic Feedback

Compared with the conventional edge-emitting lasers (EELs), the vertical cavity surface emitting lasers (VCSELs) have many own unique advantages such as low threshold current, low cost, single longitudinal mode output, small divergence angle, easy large-scale integration into two-dimensional arrays and high-coupling efficiency to optical fiber and so on. Because of the round output port and the weak anisotropy of VCSELs, the VCSELs can exhibit two orthogonal directions (X and Y), namely X polarization mode and Y polarization mode, and the VCSELs subjected to optoelectronic feedback can exhibit a variety of complex nonlinear dynamics. The current application and research situation about VCSELs are mainly focus on 850nm/980nm waveband, which are only suitable for short-distance communication. However, the reports of experimental and theoretical researches on long-wavelength VCSELs are quite scarce. The lasing wavelength of the 1550nm-VCSELs mainly located in the optical fiber zero-dispersion and low-loss window, it means the long-wavelength VCSELs have wide application prospects in high-speed and long-distance transmission.Based on the spin-flip model, the polarization switch and nonlinear dynamics of 1550nm-VCSEL subject to optoelectronic feedback have been theoretically and experimentally investigated. The results show that, the 1550nm-VCSEL subjected to negative optoelectronic feedback exhibits complex polarization when the feedback strength and feedback delay time are varied. When increasing the optoelectronic feedback strength, the phenomenon of polarization mode competition is observed. The region where bom polarization modes compete moves to lower injection currents. With further increase the feedback strength, the Y-polarization mode was completely suppressed over the entire current range; With the increase of the feedback delay time, the polarization mode competition of the VCSEL first become more and more fierce, then begin to weaken, finally tends to be stable. Meanwhile, the complex nonlinear dynamics including regular pulsing (RP), quasiperiodic pulsing (QP), chaotic pulsing (CP) states and the quasiperiodic route to chaos are numerically observed in the 1550nm-VCSEL with positive optoelectronic feedback and these are verified experimentally. The research of this paper not only can help people understand the effect of external optoelectronic feedback on long-wavelength VCSELs in chaos communication, but also has important theoretical and practical value in making the VCSELs work on some particular dynamics states through artificial regulation.