Intensity Noise Characteristics of Multimode VCSELs

The intensity noise spectra of several multi-transverse mode 1550-nm vertical-cavity surface-emitting lasers (VCSELs) have been experimentally investigated. For a VCSEL emitting in two parallel polarized transverse modes the noise spectra of the individual modes and total power show two resonance peaks. The frequencies at which both peaks appear have been measured as a function of the bias current. Our experimental results confirm the theoretical predictions of Valle Differences in the noise spectra are experimentally observed when considering a VCSEL emitting in three transverse modes with polarization instabilities. We show that additional peaks appear in the noise spectra of the total power as the bias current is increased.