Electrical Spectroscopy of Polaritonic Nanoresonators

TL;DR

This paper demonstrates the first electrical spectroscopy of polaritonic nanoresonators in 2D materials, enabling spectrally resolved detection of light confinement at the nanoscale for potential sensing and imaging applications.

Contribution

It introduces a novel electrical detection method for 2D polaritonic nanoresonators using a graphene pn-junction, combining high confinement and tunability in the mid to long-wave infrared range.

Findings

Record high-quality factors up to 200 in nanoresonators.

Prominent photocurrent peaks in the lower reststrahlen band of hBN.

Tunable resonances via geometrical and gate control.

Abstract

One of the most captivating properties of polaritons is their capacity to confine light at the nanoscale. This confinement is even more extreme in two-dimensional (2D) materials. 2D polaritons have been investigated by optical measurements using an external photodetector. However, their effective spectrally resolved electrical detection via far-field excitation remains unexplored. This fact hinders their potential exploitation in crucial applications such as sensing molecules and gases, hyperspectral imaging and optical spectrometry, banking on their potential for integration with silicon technologies. Herein, we present the first electrical spectroscopy of polaritonic nanoresonators based on a high-quality 2D-material heterostructure, which serves at the same time as the photodetector and the polaritonic platform. We employ metallic nanorods to create hybrid nanoresonators within the hybrid plasmon-phonon polaritonic medium in the mid and long-wave infrared ranges. Subsequently, we electrically detect these resonators by near-field coupling to a graphene pn-junction. The nanoresonators simultaneously present a record of lateral confinement and high-quality factors of up to 200, exhibiting prominent peaks in the photocurrent spectrum, particularly at the underexplored lower reststrahlen band of hBN. We exploit the geometrical and gate tunability of these nanoresonators to investigate their impact on the photocurrent spectrum and the polaritonic's waveguided modes. This work opens a venue for studying this highly tunable and complex hybrid system, as well as for using it in compact platforms for sensing and photodetection applications.