On-chip Ultrafast Polariton Transistors

The speed of electronic circuits has plateaued due to the limitations of transistor scaling, prompting research into all-optical logic as an alternative for high-speed computing [1]. In this direction, recent developments utilizing the strong light-matter interaction regime offered by exciton-polariton microcavities, have led to the realization of transistors at cryogenic temperature [2]. Furthermore, ultrafast transistor action [3] and NOR gate functionalities [4] have been demonstrated at room-temperature with organic semiconductors embedded in DBR vertical cavities, by exploiting polariton condensation through bosonic stimulation. Nonetheless, this vertical geometry, which has the wavevector of the polariton condensate mainly perpendicular to the substrate, necessitates the use of external free-space optics to re-route the emitted light between the individual transistors. This results in propagation delays on the order of hundreds of picoseconds that ultimately prevent the realization of scalable ultrafast circuits. This work introduces a scalable approach to room-temperature transistor functionalities in a planar architecture by employing integrated high-contrast grating (HCG) microcavities filled with an organic polymer (MeLPPP) [5]. Such a system exhibits strong light-matter coupling, confirmed by polariton condensation, characterized by a nonlinear emission increase, spectral narrowing, and blue shift (Fig. 1a). With one HCG cavity generating the pulsed in-plane control signal that constitutes the input “seed” for a second “transistor” cavity (Fig. 1b), we demonstrate transistor action on a picosecond time scale (Fig. 1c) by precisely defining the excitation scheme through a fine control of the time delay between the excitation pulses of the two cavities [6]. Hence, we observe up to 60x amplification with minimal signal distortion and a switching contrast exceeding 8. By leveraging rubust nanofabrication techniques from silicon photonics, this scalable architecture opens new possibilities for integrated all-optical logic circuits thanks to the planar on-chip nature of the signal routing.