Theoretical analysis of high-efficient dielectric nanofocusing for the generation of a brightness light source

High-brightness light sources with nanoscale volume are required in nonlinear physics studies or various nanoscale engineering areas. Although several plasmonic devices, such as plasmonic nanofocusing, have been proposed for light concentration, the efficient enhancement of the nanofocusing device to get a bright light source is still limited owing to the inevitable Ohmic loss resulting from high field confinement on metallic surface. We propose the concept of dielectric nanofocusing by reversing the concept of conventional plasmonic nanofocusing and using a three-dimensional bowtie nanoaperture (3D BNA). The optical simulations demonstrate that the 3D BNA can achieve an intensity enhancement factor of 9.01 × 10⁴. We calculate the dispersion relation for a tapered silver-SiN_x-air waveguide to prove the possibility of focusing even for a high tapered angle. The theoretically calculated modal length can explain the origin of the high intensity enhancement by proving an energy flow from the dielectric layer to the air regime in dielectric nanofocusing. The performed optical and thermal simulations demonstrate that the 3D BNA can achieve a peak intensity of 6.21 PW/cm² by avoiding the energy confinement around the metal. Our approach provides a new method for obtaining a high brightness light source.