Miniaturizable Si-based electro-optical modulator working at 1.5 μm

Abstract

Optoelectronic devices are considered the innovative element for the next generation of microelectronic integrated circuits. For this purpose, both active and passive devices—extremely miniaturized—must be implemented. We fabricated and electro-optical Si-based light intensity modulator working at 1.5 μm using a bipolar mode field-effect transistor integrated within a Si rib waveguide. The principle of operation is the light absorption by a plasma of free carriers that can be opportunely moved inside or outside of the device optical channel by properly changing the control bias. The devices, only 100 μm long, were fabricated using epitaxial Si wafers and standard clean room processing. The optical characterization at 1.48 μm in static conditions shows a modulation of ∼90% while the dynamic electrical characterization provides a switching time of ≈10ns (foreseen modulation frequency of hundreds of MHz). A modulation depth above 25% is observed for modulation frequency up to 300 kHz.