Optical trapping calculations for metal nanoparticles. Comparison with experimental data for Au and Ag spheres.
We calculate the optical forces on Au and Ag nanospheres through a procedure based on the Maxwell stress tensor. We compare the theoretical and experimental force constants obtained for gold and silver nanospheres finding good agreement for all particles with r < 80 nm. The trapping of the larger particles recently demonstrated in experiments is not foreseen by our purely electromagnetic theory based on fixed dielectric properties. Since the laser power produces a heating that may be large for the largest spheres, we propose a model in which the latter particles are surrounded by a steam bubble. This model foresees the trapping of these particles and the results turn out to be in reasonable agreement with the experimental data.
Saija
Rosalba
R
Dipartimento di Fisica della Materia e Ingegneria Elettronica, Università di Messina, Messina, Italy.
Denti
Paolo
P
Borghese
Ferdinando
F
Maragò
Onofrio M
OM
Iatì
Maria Antonia
MA
D003198:Computer Simulation; D006046:Gold / Q000737:chemistry* / Q000528:radiation effects*; D008027:Light; D008956:Models, Chemical; D054118:Nanospheres / Q000737:chemistry* / Q000528:radiation effects / Q000648:ultrastructure; D052898:Optical Tweezers; D012834:Silver / Q000737:chemistry* / Q000528:radiation effects*
D012834:Silver; D006046:Gold