Electrical Design of High-Speed Electro-Optically Modulated Coupled-Cavity VCSELs

We present an equivalent circuit cut-off frequency analysis of a Coupled-Cavity Vertical-Cavity Surface-Emitting Laser with one cavity used as a fast electro-optic modulator with lumped electrodes. We find that the mesa capacitance and the polyimide capacitance and series resistance are the most influencing parameters. In order to enhance the -3 dB bandwidth the design steps should be: reduction of the contact pad area and modulator mesa radius together with increasing the modulator cavity length, as well as implementing a pnp structure. Based on the model, we suggest a realistic structure that is theoretically able to achieve about 100 GHz modulation speed.