Improved Nano-optical Traps for Single-particle Sensing Applications

We present numerical design and simulations of nano-optical traps for single-particle sensing applications. While commonly used nano-holes with circular shapes are suitable for physically trapping nanoparticles to be detected and identified, they generate relatively weak signals in the far zone, especially when nanoparticles are small. We show that optical sensitivity of nano-holes can be enhanced significantly by using well-designed tip geometries such that metallic and dielectric nanoparticles can be detected and identified based on far-zone scattering data. Numerical simulations are performed to test the designed nano-holes and demonstrate their excellent performances in various scenarios.