A Controllable and Highly Propagative Hybrid Surface Plasmon-Phonon Polariton in a CdZnO-based Two-Interface System

TL;DR

This paper demonstrates a tunable hybrid surface plasmon-phonon polariton in a CdZnO-based system, with controllable resonance frequencies and significantly enhanced propagation lengths, advancing nanophotonic device development.

Contribution

It introduces a new hybrid mode in CdZnO systems with tunable properties and reduced losses, enabling longer-range plasmonic applications.

Findings

Hybrid SPPP mode observed and tunable via film thickness

Propagation length exceeds 500 microns, much longer than typical SPPs

Sapphire phonons enhance mode characteristics and reduce damping

Abstract

The development of new nanophotonic devices requires the understanding and modulation of the propagating surface plasmon and phonon modes arising in plasmonic and polar dielectric materials, respectively. Here we explore the CdZnO alloy as a plasmonic material, with a tunable plasma frequency and reduced losses compared to pure CdO. By means of attenuated total reflectance, we experimentally observe the hybridization of the surface plasmon polariton (SPP) with the surface phonon polariton (SPhP) in the air-CdZnO-sapphire three-layer system. We show how through the precise control of the CdZnO thickness, the resonance frequencies of the hybrid surface plasmon-phonon polariton (SPPP) are tuned in the mid-infrared, and the nature of the hybrid mode turns from a plasmon-like behavior in the thicker films to a phonon-like behavior in the thinnest films. The presence of sapphire phonons not only allows the hybrid mode to be formed, but also improves its characteristics with respect to the bare SPP. The reduced damping of the phonon oscillators allows to reduce the losses of the hybrid mode, enhancing the propagation length above 500 microns, one order of magnitude larger than that of typical SPPs, clearing the path for its application on emerging devices such as plasmonic waveguides.