Long-time dynamics of a vertical-cavity surface-emitting laser under optical feedback

External optical feedback in vertical-cavity surface-emitting laser (VCSEL) is found to influence its output intensity. We studied the effect of the amount of total output polarisation feedback and polarisation-selective feedback on the output intensities of a VCSEL for a low-resolution sampling and for long temporal duration. A resolution time-series correlation analysis is performed for different feedback conditions and the characteristic dynamics is investigated. We found a correlated fluctuation in VCSEL output for a moderate amount of total feedback and polarised feedback. The period of such fluctuations is found to be reduced from total feedback to the polarised feedback of the system.