Design of High Efficiency Multi-GHz SiGe HBT Electro-Optic Modulator

Abstract

We design and theoretically analyze a heterojunction bipolar transistor (HBT) electro-optic (EO) modulator with a composition graded SiGe base. The waveguide has a large cross-section of 1 microm for ease of fiber alignment. At a base-emitter bias of V BE = 2.5 V, a pi-phase shift requires 74.5 microm interaction length for TM polarization at lambda = 1.55 microm. The total optical attenuation is 3.9 dB to achieve a pi-phase shift in this condition. This device is expected to operate at a switching speed of 2.4 GHz.