Concave microlens assisted optoplasmonic trapping in Au nanohole

Utilizing the dielectric microstructure to confine optical energy, this work significantly enhances localized surface plasmon resonance (LSPR) effects for superior light-matter interaction. This study introduces an optoplasmonic tweezer integrated with a concave dielectric microlens and the metal thin-film system, engineered for efficient nanoparticle trapping and dynamic manipulation. Using finite element analysis, we optimized the size and spacing of Au nanoparticles (AuNPs) on the thin film to maximize the electric field intensity in the nanohole on the Au film. The structural parameters of the designed concave microlens were also investigated to optimize light confinement while enabling fluid transportation function. The results demonstrate that the optoplasmonic tweezer we proposed can achieve an approximately 400-fold enhancement of the electric field within the Au nanohole, exhibiting exceptional performance in trapping nanoparticles in a fluid. We propose an optoplasmonic structure composed of concave microlens and AuNPs, which can enable simultaneous integration both microfluidic channels and trap nanoparticles, providing a new idea for trapping nanoparticles in fluids.