Integrated ultra-fast all-optical transistor

The clock frequency of electronic circuits has been stagnant at a few gigahertz foralmost two decades because of the breakdown of Dennard scaling, which suggeststhat by miniaturizing transistors, they can run faster while consuming the samepower[1]. Optical-based computing offers a potential solution to this challenge[2].However, the lack of materials with sufficiently strong nonlinear interactions necessaryfor achieving all-optical switches led to large device sizes and high optical energyrequirements that hindered scalable architectures. Recently, microcavities utilizingpolymers as photoactive material in the regime of strong light-matter interaction haveenabled the development of all-optical transistors[3] capable of operating at roomtemperature with switching times below one picosecond[4]. Nonetheless, the realizationof complex circuits was restricted due to limitations posed by non-integrated verticalcavity geometry. Here, by leveraging silicon-on-insulator technology, we realize fullyintegrated metamaterial-based high-index contrast grating (HCG) microcavities filledwith an organic polymer (MeLPPP) as photoactive material. This platform, capable ofhosting a strong-light matter interaction regime system, shows integrated on-chipexciton-polariton condensation at ambient conditions. Furthermore, by exploiting theoutcoupling resonance from one (control) cavity as input for the next (transistor) cavity,through seeded polariton condensation, we demonstrate ultrafast all-optical transistoraction with switching time in the order of 1ps[5]. Finally, the coupling of two resonatorsproves the cascadability of this technology which paves the way for the implementationof more complex logic circuits.