Investigation On Polarization Switch And Nonlinear Dynamics Of1550nm-VCSELs With Optical Feedback

Compared with the traditional edge-emitting lasers, the vertical cavity surface emitting lasers have many advantages such as single longitudinal mode output, small divergence angle, low loss, well array integration, possibility for on-wafer test, lower costs and so on. Because of the round output port and the weak anisotropy of VCSELs, the VCSELs have more complex nonlinear dynamics with the optical feedback. The current application and research situation about VCSELs are mostly focus on850nm/980nm waveband, which are only suitable for short distance communication and the reports-of experimental and theoretical researches on long-wavelength VCSEL are quite bland. However, when the light propagating in the optic fiber has low-loss area in the1550nm wave band, it means the long-wavelength VCSEL has wide application prospects.Based on the framework of the spin-flip model (SFM), the nonlinear dynamics of1550nm-VCSELs subject to polarization-preserved optical feedback have been theoretically investigated. The results show that, for a free-running1550nm-VCSEL, the current value for polarization switching (PS) is affected seriously by the internal parameters; with the increase of the gain anisotropy coefficient γa, the corresponding current for PS is increased. Due to the introduction of the polarization-preserved optical feedback, the dominant polarized mode (Y polarized mode) will display different dynamical states for different injection currents while the other mode (X polarized mode) may be excited. As a result, the average output powers of the two polarized modes are increased along with fluctuation with the increase of current. For different feedback times, the dynamics states of1550nm-VCSELs with polarization-preserved optical feedback maybe route into chaos via by different evolution paths such as period doubling bifurcation, quasi-periodic bifurcation and intermittent chaos. The signifcance of this paper can help people understand the effect of external optic feedback on long-wavelength VCSEL and make the VCSELs works on the particular dynamics state.