Fig. 1. Schematic diagram of structural model proposed in this study. (a) The formation of the hybrid mode. (b) The twistedly and vertically aligned MIM structure realized with the rotation of θ. (c) The proposed periodic array of the MIM structure with LCP and RCP plane waves.

Fig. 2. Transmission spectra of MIM structures for (a) LCP and (b) RCP plane waves with different twisted angles at 0^o, 30^o, 60^o, and 90^o, respectively. (c) The detailed transmission spectra of the MIM structure with twisted angles θ varied from 90^o to 0^o with a step of 10° for LCP and RCP plane waves, respectively. The radius of the nanodisks is 220 nm, and the gap in the disk is 50 nm.

Fig. 3. Simulated charge distributions of the top and bottom nanogaps twistedly stacked with (a) 0^o, (b) 90^o, (c) 30^o, and (d) 60^o, excited with LCP and RCP plane waves at the wavelength of 1550 nm, respectively. Simple drawing for charge oscillations of the same structures with the twisted angle of (e) 0^o, (f) 90^o, (g) 30^o, and (h) 60^o, excited with LCP and RCP plane waves at the wavelength of 1550 nm, respectively. Inset in (h): SP mode and gap mode for the same structure with LCP and RCP plane waves, respectively.

Fig. 4. Calculated magnetic near-field distributions of top and bottom nanogaps twistedly stacked with (a) 0°, (b) 90°, (c) 30°, and (d) 60°, excited with LCP and RCP plane waves at the wavelength of 1550 nm, respectively.

Fig. 5. CD signals of the MIM structure impacted by twisted angles varied from 0° to 90°. (a) ΔT spectrum for structures twisted from 0° to 90° with a step of 10°. The maximum CD signal is achieved with the twisted angle of 60°, as the red arrow marks. (b) Grayscale image of the CD signal (ΔT) impacted by the twisted angle and plane wave wavelength. The maximum CD signal is achieved at 1550 nm for the twisted angle of 60°, as the green star marks.

Fig. 6. (a) Maximum of CD (ΔT) with varied Au nanodisk radius from 120 nm to 250 nm, in which the red shift with the increasing nanodisk radius is marked by the dash line. (b) Maximum of CD (ΔT) with varied refractive index n from 1.38 to 1.46, in which the red shift with the increasing refractive index is marked by the dash line.