Optical trapping of Au-Fe alloyed nanoparticles: a theoretical calculation

Magnetoplasmonic nanoparticles, such as Au-Fe alloys, are very interesting for their properties. In this article, the optical trapping of Au-Fe nanoparticles are investigated as a function of Fe atomic percent doped in gold nanoparticles, theoretically. Using a generalized Lorenz-Mie theory, it is shown that the maximum force exerted on the alloyed nanoparticles enhances about 75% with increasing Fe atomic percent. It is shown that the trapping strength is depth-dependent and shows a 20% increment in shallow positions and a 17% decrement in the axial direction in the optimal depth, which is 7 mu m deep inside the sample. Wavelength dependence of alloyed nanoparticles is studied too.