Critical study of the Vertical-Cavity Surface Emitting Lasers (VCSEL) electrical access for integrated optical sub-assembly

The proposal contribution aims at highlighting the consequence of the impedance mismatching in VCSEL-based optical subassembly for optical interconnection applications. The integration of this micro-laser diode to an optical interconnection module needs a particular care to avoid electromagnetic coupling which could transform the advantage of the VCSEL technology in a weakness. Indeed, the vertical emission perpendicular to the active layer gives the possibility to achieve the need of planarization of the optoelectronic circuits and the design of VCSEL arrays. That is why it is of great interest to develop an optoelectronic model including the electrical access effect. This model is based on the VCSEL rate equation comparison with a behavioral small-signal equivalent circuit. Scattering parameters of various VCSEL structures and various VCSEL chip submounts are tested. This characterization allows the validation of the laser model and emphasizes the influence of the electrical access during the light transmission. In a particular VCSEL array structure, a crosstalk phenomenon is also observed. This crosstalk increases strongly with increase in the frequency. Consequently the electrical access to the VCSEL needs to be improved in order to avoid an inadequate utilization of the VCSEL.