关键词: waveguide, anisotropic materials, near-field imaging, van der Waals materials

Abstract: The unique in-plane and out-of-plane anisotropy of $\alpha $-MoO$_{3}$ 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 $\alpha $-MoO$_{3}$ by near-field imaging of the waveguide modes along the [100] and [001] directions of $\alpha $-MoO$_{3}$ 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 $\alpha $-MoO$_{3}$ in device applications. Our findings enhance the field of research into $\alpha $-MoO$_{3}$, highlighting its utility in fabricating next-generation optoelectronic devices due to its unique optically anisotropic waveguide.

Key words: waveguide, anisotropic materials, near-field imaging, van der Waals materials