Mode partition noise in vertical cavity surface emitting lasers

In vertical cavity surface emitting lasers (VCSELs), a single longitudinal mode is supported in a cavity that can allow multiple transverse modes. In contrast to edge emitting lasers where multiple modes are longitudinal with nearly identical transverse profile, transverse modes can have significant differences in their coupling efficiency. Hence, mode selective loss (MSL) is easily introduced and mode partition noise (MPN) is more significant to the intensity noise of VCSELs. In this paper, we discuss the relevant time scales of the mode partition dynamics of VCSELs and explain the low frequency dependence of the relative intensity noise (RIN) spectrum.