Waveguide HBT electroabsorption modulators: devices and circuits

Abstract

We show the monolithic integration of HBT and EAM which are merged to a combined device able to operate as an electronic and optical component (HBT-EAM) simultaneously. Comparison to a pure EAM made from the same InP-based layer stack gives an improved optical modulation contrast up to 20GHz. To demonstrate the concept a differential amplifier is built which results in a voltage gain of 8 at 2.55GHz, limited mainly due to a load resistor of 500R. To improve optical modulation an InGaAlAs-base is realized to give better contrast up to IO&, while the DC current gain is at 3.5 and has to be optimized.