Modulation response, impedance, and equivalent circuit of ultra-high-speed multi-mode VCSELs

Abstract

To establish highly performing vertical cavity surface-emitting lasers (VCSELs), it is essential to have an adequate understanding of the intrinsic laser dynamics of these devices. However, this is done while bearing in mind that extrinsic parasitic elements in VCSELs play an important role in limiting the intrinsic modulation bandwidth. Compared to largesignal analyses, the small-signal modulation response of a VCSEL can be isolated from the entire system, thus providing accurate information on the intrinsic laser dynamics. An alternative approach to that of using the rate equations is to transform theses rate equations to an equivalent circuit model. In this work, we firstly present advanced electrical circuit modeling of the intrinsic dynamic performance of multi-mode VCSELs, for the case where lasing modes do not share a common carrier reservoir. The electrical circuit model is derived from innovative advanced multi-mode rate equations that take into account the effect of spatial hole burning, gain compression, and inhomogeneity in the injection current. Secondly, we analyse different electrical parasitic equivalent circuit models in the aim of comparing them and selecting the one that can best describe and represent the physical properties of our high-performance VCSELs. Through measuring the microwave reflection coefficient S11(f) and fitting it into the calculated counterpart from the equivalent-circuit impedance model, the parasitic components of the equivalent circuit model are extracted.