Design and modeling of asymmetric bow-tie VCSELs for 100 GHz and beyond

We present the design and numerical analysis of an asymmetric bow-tie vertical-cavity surface-emitting laser (ABT-VCSEL) that enables PAM-2 direct modulation up to 100 GHz. The device concept relies on photon-photon resonance (PPR) between laterally coupled modes, triggered by a structural asymmetry introduced via a hollowed dielectric mirror. This approach avoids the need for asymmetric pumping and probing while ensuring strong modal coupling under uniform carrier injection. A dynamical in-house suite, combining field-carrier interaction, electromagnetic, and thermal problems, is developed and discussed to evaluate device performance under realistic conditions. The simulation results predict a 3-dB bandwidth up to 70 GHz with low modulation swing, and open eye diagrams at 100 GHz PAM-2 modulation and 70 GHz PAM-4 modulation. The proposed ABT-VCSEL concept shows robustness against geometrical variations and ambient temperature when proper cavity detuning is applied, making it a promising candidate for next-generation ultra-fast short-reach interconnects.