# Ultrafast and energy-efficient all-optical switching with graphene-loaded deep-subwavelength plasmonic waveguides

## TL;DR

This paper demonstrates ultrafast, energy-efficient all-optical switching using graphene-loaded deep-subwavelength plasmonic waveguides, achieving record-low switching energy and sub-picosecond switching times for integrated photonic circuits.

## Contribution

It introduces a novel graphene-loaded plasmonic waveguide design that significantly enhances optical nonlinearity, enabling ultrafast, low-energy all-optical switching at the nanoscale.

## Key findings

- Switching energy of 35 fJ achieved
- Switching time of 260 fs demonstrated
- Device compatible with silicon photonics

## Abstract

All-optical switches have attracted attention because they can potentially overcome the speed limitation of electric switches. However, ultrafast, energy-efficient all-optical switches have been challenging to realize due to the intrinsically small optical nonlinearity in existing materials. As a solution, we propose graphene-loaded deep-subwavelength plasmonic waveguides (30 nm x 20 nm). Thanks to extreme light confinement, we have significantly enhanced optical nonlinear absorption in graphene, and achieved ultrafast all-optical switching with a switching energy of 35 fJ and a switching time of 260 fs. The switching energy is four orders of magnitudes smaller than that in previous graphene-based devices and is the smallest value ever reported for any all-optical switch operating at a few picoseconds or less. This device can be efficiently connected to conventional Si waveguides and employed in Si photonic integrated circuits. We believe that this graphene-based device will pave the way towards on-chip ultrafast and energy-efficient photonic processing.

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Source: https://tomesphere.com/paper/1907.01764