Bias level dependence of turn-off oscillations in vertical-cavity surface-emitting lasers

Abstract

Turn-off oscillations are dynamical phenomena that appear when modulating the current applied to vertical-cavity surface-emitting lasers (VCSELs). These phenomena consist of the generation of significant pulsed optical power, while the laser current remains at the lowest (bias) value during the modulation. We study the dependence of turn-off oscillations on the bias current for both single-mode and multitransverse-mode VCSELs. We show that as the bias current increases, the maximum power of these oscillations obtained with multimode lasers becomes similar to the one obtained with single-mode lasers. A criterion for obtaining the bias current above which turn-off oscillations are no longer dominated by spatial effects is given. We also show that the transverse spatial profile of the light emitted in multimode VCSELs during turn-off oscillations depends on the value of the bias current.