Unveiling the in-plane anisotropic dielectric waveguide modes in α-MoO₃ flakes

The unique in-plane and out-of-plane anisotropy of α-MoO₃ has attracted considerable interest with regard to potential optoelectronic applications. However, most research has focused on the mid-infrared spectrum, leaving its properties and applications in the visible and near-infrared light spectrum less explored. This study advances the understanding of waveguiding properties of α-MoO₃ by near-field imaging of the waveguide modes along the 100 and 001 directions of α-MoO₃ flakes at 633 nm and 785 nm. We investigate the effects of flake thickness and documented the modes’ dispersion relationships, which is crucial for tailoring the optical responses of α-MoO₃ in device applications. Our findings enhance the field of research into α-MoO₃, highlighting its utility in fabricating next-generation optoelectronic devices due to its unique optically anisotropic waveguide.