Fig. 1. Schematic diagram of MIM structure, which consists of the gold cladding layers and the air gap as the core layer. The dielectric constants of gold and air are ε_Au = 12.997 + 1.0341i and ε₀ = 1, respectively. The thickness of the air gap is d = 60 nm. The plasmonic modes propagate towards the origin from all spatial directions to create the superchiral field.

Fig. 2. Distribution of light field components and g-factor enhancement for the superchiral spot. (a) H_|| in the xz plane, (b) E_z in the xz plane, (c) E_z in the xy plane, (d) E_|| in the xz plane, (e) g/g_CPL in the xz plane, and (f) g/g_CPL in the xy plane.

Fig. 3. Schematic diagram of the focusing system to generate a superchiral spot by the plasmonic mode in the MIM structure.

Fig. 4. (a) Amplitudes of the transverse component of the magnetic field, (b), (c) amplitudes of the z component and transverse component of the electric field, (d) g-factor enhancement of the superchiral spot.

Fig. 5. (a) Positions of the superchiral spots when θ/θ_NA = 0.9, 0.92, 0.94, 0.96, 0.98, 0.999 for d = 60 nm. The colorbar represents the g-factor enhancement (i.e., g/g_CPL). h is the z position of the superchiral spot, and d is the thickness of the air gap. (b) The relationship between the position of the superchiral field and the incident angle θ when the thickness of the air gap is 50 nm, 60 nm, 70 nm, and 80 nm.