Figure 3.

(a) Schematics of a 225-nm-thick α-MoO₃ slab on a SiO₂ substrate in which propagating PhPs are depicted by elliptical fringes (represented in red and blue). A vertically oriented electric point dipole placed on top of the structure provides concentrated electric fields that allow for launching PhPs at an incident wavelength ${\omega }_0=$ 979 cm⁻¹ (elliptic regime). (b) Simulated electric field profiles (dots), Re(E_z), along the [100] and [001] crystal directions of α-MoO₃ for an incident frequency ${\omega }_0=$ 905 cm⁻¹ (hyperbolic regime) and ${\omega }_0=$ 979 cm⁻¹ (elliptic regime). The fit to the simulated profiles are depicted with a black solid line.