Two-dimensional metal oxide polaritonics.

Two-dimensional (2D) metal oxides (MOs) are crucial materials in semiconductor optoelectronics and energy applications. Recently, ultra-confined and anisotropic polaritons, which are hybrid light-matter waves, in 2D MOs have renewed interest in the field of nanophotonics. With natural abundance, diverse compositions, and rich symmetries, MOs exhibit a wide range of electromagnetic responses from the visible to terahertz spectral range, providing various polariton platforms for designing on-chip photonic integrated circuits. In this Review, we discuss crystal symmetry and polaritons in MOs, present intrinsic and extrinsic manipulation approaches, and summarize strategies for synthesizing 2D polaritonic MOs. We also propose 2D MO-based polaritonic device architectures for use in heat management, photonics, and biosensing, all of which could be integrated into future photonic chips. Overall, with the rapid flourishing of 2D MO polaritonics, this review aims to stimulate further exploration and innovation for next-generation on-chip photonic systems.