Launching and Manipulation of Higher‐Order In‐Plane Hyperbolic Phonon Polaritons in Low‐Dimensional Heterostructures

• Published in: Advanced materials (Weinheim) 2023-06, Vol.35 (22), p.e2300301-n/a
• Main Authors: Lu, Guanyu, Pan, Zhiliang, Gubbin, Christopher R., Kowalski, Ryan A., De Liberato, Simone, Li, Deyu, Caldwell, Joshua D.
• Format: Article
• Language: English
• Subjects: Electromagnetic radiation; Electrons; Heterostructures; hyperbolic dispersion; hyperbolic phonon polaritons; in‐plane; Lattice vibration; low‐symmetry material; Materials science; nanowire; Nanowires; Phonons; Polaritons; Propagation modes; Silicon carbide; Wave fronts; Wave propagation
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202300301

Hyperbolic phonon polaritons (HPhPs) are stimulated by coupling infrared (IR) photons with the polar lattice vibrations. Such HPhPs offer low‐loss, highly confined light propagation at subwavelength scales with out‐of‐plane or in‐plane hyperbolic wavefronts. For HPhPs, while a hyperbolic dispersion implies multiple propagating modes with a distribution of wavevectors at a given frequency, so far it has been challenging to experimentally launch and probe the higher‐order modes that offer stronger wavelength compression, especially for in‐plane HPhPs. In this work, the experimental observation of higher‐order in‐plane HPhP modes stimulated on a 3C‐SiC nanowire (NW)/α‐MoO3 heterostructure is reported where leveraging both the low‐dimensionality and low‐loss nature of the polar NWs, higher‐order HPhPs modes within 2D α‐MoO3 crystal are launched by the 1D 3C‐SiC NW. The launching mechanism is further studied and the requirements for efficiently launching of such higher‐order modes are determined. In addition, by altering the geometric orientation between the 3C‐SiC NW and α‐MoO3 crystal, the manipulation of higher‐order HPhP dispersions as a method of tuning is demonstrated. This work illustrates an extremely anisotropic low dimensional heterostructure platform to confine and configure electromagnetic waves at the deep‐subwavelength scales for a range of IR applications including sensing, nano‐imaging, and on‐chip photonics. Highly confined, directionally dependent in‐plane hyperbolic light propagation is demonstrated in a heterostructure composed of a 3C‐SiC nanowire on α‐MoO3 flake. Such low‐dimensional heterostructure showcases the efficient and precise manipulation of the extremely anisotropic light‐matter interactions at the deeply subwavelength scale, opening opportunities for a wide range of IR applications.