Exciton-Polaritons in Carbon Nanotube Crystals with Tunable Anisotropy

Abstract Anisotropy can endow optical systems with polarization sensitivity and nontrivial band structures, which are crucial for polarization manipulation, topological photonics, and related device applications. Here, we show that an aligned thin film of single-walled carbon nanotubes (CNTs) within a planar microcavity behaves as a uniaxially anisotropic crystal, which endows the resulting polariton system with strong polarization selectivity and tunable light–matter coupling. By introducing orientational disorder, the CNT film transforms into a biaxial crystal characterized by the emergence of two orthogonally polarized polariton branches and distinct polarization splitting, which enables the construction of topologically nontrivial band architectures. By developing a quantum model for polariton systems based on one-dimensional emitter ensembles, we establish a quantitative correlation between polarization splitting and orientational disorder. Our work demonstrates that aligned CNT microcavities serve as a highly flexible and versatile platform for studying anisotropic near-infrared exciton-polaritons, which can build a bridge between polarization-controlled optics, topological photonics, and non-Hermitian physics.