Ablation and optical third-order nonlinearities in ag nanoparticles

International Journal of Nanomedicine
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Ablation and optical third-order nonlinearities in Ag nanoparticles
This article was published in the following Dove Press journal: International Journal of Nanomedicine 17 November 2010 Number of times this article has been viewed

carlosTorres-Torres 1 Néstor Peréa-López 2 Jorge Alejandro reyes-esqueda 3 Luis rodríguez-Fernández 3 Alejandro crespo-sosa 3 Juan carlos cheang-Wong 3 Alicia Oliver 3
section of graduate studies and research, school of Mechanical and electrical engineering, National Polytechnic Institute, Zacatenco, Distrito Federal, Mexico; 2Laboratory for Nanoscience and Nanotechnology research and Advanced MaterialsDepartment, IPIcYT, camino a la Presa san Jose, san Luis Potosi, Mexico; 3Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, México, D.F. 01000, México
1

Abstract: The optical damage associated with high intensity laser excitation of silver nanoparticles (NPs) was studied. In order to investigate the mechanisms of optical nonlinearity of a nanocomposite and theirrelation with its ablation threshold, a high-purity silica sample implanted with Ag ions was exposed to different nanosecond and picosecond laser irradiations. The magnitude and sign of picosecond refractive and absorptive nonlinearities were measured near and far from the surface plasmon resonance (SPR) of the Ag NPs with a self-diffraction technique. Saturable optical absorption and electronicpolarization related to self-focusing were identified. Linear absorption is the main process involved in nanosecond laser ablation, but nonlinearities are important for ultrashort picosecond pulses when the absorptive process become significantly dependent on the irradiance. We estimated that near the resonance, picosecond intraband transitions allow an expanded distribution of energy among the NPs, incomparison to the energy distribution resulting in a case of far from resonance, when the most important absorption takes place in silica. We measured important differences in the ablation threshold and we estimated that the high selectiveness of the SPR of Ag NPs as well as their corresponding optical nonlinearities can be strongly significant for laser-induced controlled explosions, withpotential applications for biomedical photothermal processes. Keywords: nonlinear optics, laser irradiation, metallic nanoparticles, Kerr effect, nonlinear optical absorption

Introduction
It has been noted that the physical features of formation and interaction of metallic nanoparticles (NPs) are quite specific at different wavelengths of irradiation.1 The optical response of NPs differs drasticallyfrom conventional materials2 and, particularly, they exhibit important changes strongly influenced by surface plasmon resonance (SPR) excitations.3–5 Their powerful and fast optical nonlinear response make them attractive for applications in some areas like photonics6 or plasmonics,7 but it seems that they are extraordinarily valuable for biomedical functions such as controlled drug delivery,8genomics research,9 targeting,10 diagnosis,11 and therapeutic applications.12 Because of their distinctive optical properties and biocompatibility, Au NPs have proven to be powerful tools in various nanomedicinal and nanomedical applications.13 Nevertheless, recent advances in the use of NPs in medicine include research on Ag NPs mainly due to their interesting sensitivity given by SPR properties14,15because excitations of the SPR could produce scattering and absorption that are easily controlled by tuning the structural orientation of the NPs.16,17 The SPR excitation of metallic NPs is an extremely useful property for in vivo imaging techniques such as photoacoustics18

correspondence: carlos Torres-Torres section of graduate studies and research, school of Mechanical and electrical...