**7. Single unit plasmonic bowtie nano-antenna**

Bowtie shape PNAs (PBNAs) can transfer the light field efficiently by converting the light from external space into a subwavelength spectral region with the improvement at an optical wavelength in a tiny area between its antenna arms.

First of all, initial dimensions are selected to design primary bowtie shape nanoantenna by sitting the length of nano-antenna is (L), the width is (W), the thickness is (T), the apex width is (A), the gap width is (G) and the bowtie apex angle is (Θo) [30], as shown in **Figure 1a**.

The bowtie structure is normally illuminated by linearly polarized waveguide excitation source along the x-axis (x-polarization). The surrounding environment of the design structure is assumed to be air. as shown in **Figure 1b**.
