# Integrated, ultrafast all-optical polariton transistors with sub-wavelength grating microcavities

## TL;DR

Researchers developed a compact, ultrafast all-optical transistor using silicon photonics and organic materials, enabling faster and scalable optical computing.

## Contribution

A scalable, in-plane integrated all-optical transistor with picosecond switching and high amplification using sub-wavelength grating microcavities.

## Key findings

- Achieved exciton-polariton condensation at room temperature in integrated microcavities.
- Demonstrated picosecond switching and 60x amplification with an 8:1 extinction ratio.
- Device has a 2 × 2 µm2 footprint suitable for on-chip integration.

## Abstract

All-optical logic has the potential to overcome the operation speed barrier that has persisted in electronic circuits for two decades. However, the development of scalable architectures has been prevented so far by the lack of materials with sufficiently strong nonlinear interactions needed to realize compact and efficient ultrafast all-optical switches with optical gain. Microcavities with embedded organic material in the strong light-matter interaction regime have recently enabled all-optical transistors operating at room temperature with picosecond switching times. However, the vertical cavity geometry, which is predominantly used in polaritonics, is not suitable for complex circuits with on-chip coupled transistors. Here, by leveraging state-of-the-art silicon photonics technology, we have achieved exciton-polariton condensation at ambient conditions in fully integrated high-index contrast sub-wavelength grating microcavities filled with a π-conjugated polymer as optically active material. We demonstrate ultrafast all-optical transistor action by coupling two resonators and utilizing seeded polariton condensation. With a device area as small as 2 × 2 µm2, we realize picosecond switching and amplification up to 60x, with extinction ratio up to 8:1. This compact ultrafast transistor device with in-plane integration is a key component for a scalable platform for all-optical logic circuits that could operate two orders of magnitude faster than electronic counterparts.

Using integrated silicon high-contrast sub-wavelength gratings and organic cavity exciton-polaritons at room temperature, we realize all-optical transistor action with picosecond switching and amplification, as well as ultracompact footprint.