High-speed electro-absorption modulator based on sige HBT

In this paper, we propose a silicon electro-absorption modulator (EAM) that is based on the NPN SiGe Heterojunction Bipolar Transistor (HBT). The SiGe HBT EAM is a carrier-injection type device in which electrons are injected from the emitter to the base and the collector region. Compared to other silicon-based injection-type modulators, the HBT optical modulator has the advantages of small footprint, high switching speed, and low driving voltage. Unlike phase modulator, the HBT EAM directly modulates light intensity; therefore, it does not require Mach-Zehnder Interferometer (MZI) or resonant cavity structures to convert phase information into the intensity for incoherent detection. As a result, the EAM design is simpler than the Electro-Optic (EO) modulator and consumes less surface area on a chip.