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

• Published in: ACS photonics Vol. 6; no. 11; pp. 2816 - 2822
• Main Authors: Tamayo-Arriola, Julen, Castellano, Eduardo Martínez, Bajo, Miguel Montes, Huerta-Barberà, Adelaida, Muñoz, Elias, Muñoz-Sanjosé, Vicente, Hierro, Adrian
• Format: Journal Article
• Language: English
• Published: American Chemical Society 20-11-2019
• Subjects: propagation length; CdZnO; mid-infrared plasmonics; hybridization; surface plasmon−phonon polariton
• ISSN: 2330-4022; 2330-4022
• DOI: 10.1021/acsphotonics.9b00912

The development of new photonic 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 with the surface phonon polariton 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 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 it also improves its characteristics with respect to the bare surface plasmon polariton. The reduced damping of the phonon oscillators allows to reduce the losses of the hybrid mode, enhancing the propagation length above 500 μm, 1 order of magnitude larger than that of typical surface plasmon polaritons, clearing the path for its application on emerging plasmonic devices working in the mid-infrared spectral range.