The Research Of Optical Trapping With Low Power Based On A Palladium Nanorod Pair Array

Optical trapping is currently widely applied in many fields, especially bioscience field. In this field, one critical issue is to trap and manipulate small bio-particles without damaging them. The plasmonics-assisted optical trapping method is considered to be vary promising for achieving more precise trapping of small particles compared to the conventional optical trapping method. The optical trapping force generated by plasmonics-assisted optical trapping is largely increased, because of the use metal nanostructure and stimulating the surface plasmon polaritons which can make local light field enhance and near-field light intensity increase. In recent years, it is widely attention that how to make use of surface plasmon optical tweezers to obtain greater optical force so as to realize the complex operation of micro-nano particles. Based on surface plasmon resonance,this article proposes surface plasmon optical tweezers based on metal palladium nanorod pair array which can produce greater optical trapping force with low incident power.In this article, firstly, we give a brief summary of the history of the development of optical trapping and its applications. Then we introduce the basic principle of optical tweezers and three kinds of calculation methods of optical trapping force. Finally, we analyze and simulate the plasmonics-assisted optical trapping based on a palladium nanorod pair array. We also design the experiment to prove our theoretical conclusions.Here, we present a more direct approach to create a nanonewton optical force trap by simply illuminating a palladium nanorod pair array deposited on a substrate and study the trapping behavior of the nanospheres under such optical trap. At resonance, we study the optical force acting on the nanoparticle with different positions based on the method of Finite Element Analysis (FEA) and Maxwell stress tensor. We get that the maximum of optical force is about 5.5 nN with input power 200mW. Compared with other surface plasmon optical tweezers, the force is increased to three or four times and even an order of magnitude. Numerical simulation results show that nanoparticles can be captured near the center closed to the gap between the nanorod pair. In addition, we present the quantitative relationship of resonance wavelength changes with the parameters of the nanostructure. Our optical trapping nanostructure has great potential to trap nanoparticles and may be easily integrated into a small chip for some transdisciplinary applications because of its simple structure.