Dynamics of 980 nm VCSELs Characterized Using Temperature Dependent RIN Spectra

High speed optical interconnects are replacing copper connections in ever shorter link distance, low cost, high speed communication systems employing directly modulated laser diodes. In very short distance systems ($<$1 m), laser diode bandwidth is a major limitation. Laser intensity noise spectra contain valuable information on laser dynamics including resonant frequency and damping. In this work, vertical cavity surface emitting lasers (VCSELs) are fabricated from a metal-organic chemical vapor deposition (MOCVD) grown AlGaAs structure on an n-type substrate. The intrinsic resonance frequency and damping constant of 980 nm VCSELs are measured. Two methods are used: constant temperature and varying injection current and constant injection current with varying temperature. After fitting the spectra to the conventional damped oscillator model to extract resonance frequency and damping, K-factor analysis is performed both on the conventional constant temperature data as well as the constant current data. The results of the two approaches are compared.