Stimulated plasmon polariton scattering

C Wolff,N A Mortensen

doi:10.1038/s41467-020-17810-4

Abstract

Plasmon and phonon polaritons of two-dimensional (2D) and van-der-Waals materials have recently gained substantial interest. Unfortunately, they are notoriously hard to observe in linear response because of their strong confinement, low frequency and longitudinal mode symmetry. Here, we propose an approach of harnessing nonlinear resonant scattering that we call stimulated plasmon polariton scattering (SPPS) in analogy to the opto-acoustic stimulated Brillouin scattering (SBS). We show that SPPS allows to excite, amplify and detect 2D plasmon and phonon polaritons all across the THz-range while requiring only optical components in the near-IR or visible range. We present a coupled-mode theory framework for SPPS and based on this find that SPPS power gains exceed the very top gains observed in on-chip SBS by at least an order of magnitude. This opens exciting possibilities to fundamental studies of 2D materials and will help closing the THz gap in spectroscopy and information technology.

Highlights

Plasmon and phonon polaritons of two-dimensional (2D) and van-der-Waals materials have recently gained substantial interest
The most promising avenue to overcome the extreme wave number mismatch between polaritons and free-space radiation is by scattering at discontinuities, e. g. introduced by the probe of a scanning near-field optical microscope (SNOM), or material discontinuities designed into the device[9]
In the remainder of this paper, we describe the principle of stimulated plasmon polariton scattering (SPPS) and conclude that it is experimentally observable in a standard silicon slot waveguide covered with an appropriately biased graphene monolayer

Summary

Introduction

Plasmon and phonon polaritons of two-dimensional (2D) and van-der-Waals materials have recently gained substantial interest. The generation of graphene plasmon polaritons by difference-frequency generation based on the intrinsic nonlinearities has been studied both theoretically[10,11] and experimentally[12] This has led to significant insights[13], but is somewhat inefficient and does not seem very practical for applications beyond fundamental research. From its initial status as an academic curiosity, it has soon proven invaluable to characterize mechanical properties of materials at GHz frequencies—a difficult range for direct mechanical measuring techniques It has attracted considerable attention for the realization of flexible yet highly selective optical filters[17], novel light sources[18], the processing and buffering of optical signals[19,20], and for the generation and amplification of coherent hypersonic waves, e.g. following the concept of the so-called phonon laser[21]. In the remainder of this paper, we describe the principle of SPPS and conclude that it is experimentally observable in a standard silicon slot waveguide covered with an appropriately biased graphene monolayer

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Conclusion