Figure 1.

Sketch of the dual-width plasmonic grating structure, on a Si substrate containing a layer of SiO₂, with finite thickness: (a) shows a 3D representation of the structure and the generation of plasmonic hot spots within the area of a diffraction-limited Gaussian beam; (b) shows a 2D cross-section of the structure in (a) as designed in the computational models. The structure widths (w₁ and w₂), spacing width (g), period (P), and SiO₂ thickness (t_SiO2) are labeled, along with the incident wavelength (λ₀), propagation direction (k), and electric field polarization (E₀).