The shape and alignment of silver nanoparticles embedded in a glass matrix is controlled using silicon ion irradiation. Symmetric silver nanoparticles are transformed into anisotropic particles whose larger axis is along the ion beam. Upon irradiation, the surface plasmon resonance of symmetric particles splits into two resonances whose separation depends on the fluence of the ion irradiation. Simulations of the optical absorbance show that the anisotropy is caused by the deformation and alignment of the nanoparticles, and that both properties are controlled with the irradiation fluence. *

High-energy metallic ions were implanted in silica matrices, obtaining spherical-like metallic nanoparticles (NPs) after a proper thermal treatment. These NPs were then deformed by irradiation with Si ions, obtaining an anisotropic metallic nanocomposite. An average large birefringence of 0.06 was measured for these materials in the 300-800 nm region. Besides, their third order nonlinear optical response was measured using self-diffraction and P-scan techniques at 532 nm with 26 ps pulses. By adjusting the incident light's polarization and the angular position of the nanocomposite, the measurements could be directly related to, at least, two of the three linear independent components of its third order susceptibility tensor, finding a large, but anisotropic, response of around 10(-7) esu with respect to other isotropic metallic systems. For the nonlinear optical absorption, we were able to shift from saturable to reverse saturable absorption depending on probing the Au NP's major or minor axes, respectively. This fact could be related to local field calculations and NP's electronic properties. For the nonlinear optical refraction, we passed from self-focusing to self-defocusing, when changing from Ag to Au.

A large optical birefringence of oriented Ag nanoellipsoids embedded in silica was measured using an ellipsometric technique. The two main surface plasmon resonances associated with the axes of the ellipsoid were tuned, allowing us to quantify the light transmission through the samples when placed and rotated between crossed and parallel polarizers. This birefringence can be physically associated with the selective optical absorption of one component of the linear polarization of the incident light with respect to the anisotropic axis of the sample, depending on the wavelength used to perform the measurement.

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Significant changes in the optical properties of nanometer-size Ag clusters embedded in high-purity silica were obtained. Samples were prepared by 2 MeV Ag-ion implantation with fluences in the 2.8–3.8×1016 ions/cm2 range and subsequent annealing at various temperatures in air (oxidizing atmosphere) or in a hydrogen-rich atmosphere (reducing atmosphere). Changes consisted of large and small blueshifts of the resonance surface plasmon peak position, light absorption modification in the ultraviolet (UV) region, increased optical extinction in all the spectrum wavelength range, and different resonance peak height depending on annealing atmosphere. Optical property changes were analyzed in terms of Ag cluster size, interaction at cluster–matrix interface, cluster hydrogen content, diffusivity and conductivity. Bands in the UV region are reported.

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In this paper, Au nanoparticles obtained by ion implantation and a subsequent thermal annealing have been elongated in a privileged direction by means of a postannealing 10 MeV Si ion irradiation. The modification and splitting of the surface plasmon resonance peak were determined by optical extinction spectroscopy, changing the polarization angle of the incident light. Moreover, the extinction spectra were accurately fitted with the T-matrix method, showing a good agreement with the results obtained by transmission electron microscopy, Rutherford backscattering spectrometry, and grazing-incidence small-angle X-ray scattering.

Formation of Au core−Ag shell bimetallic nanoparticles in silica matrix is demonstrated through sequential implantation of Ag and Au ions and subsequent thermal annealing. Formation of core−shell structures is verified through optical absorption spectroscopy, high-resolution transmission electron microscopy, electron energy loss spectroscopy, and simulated optical extinction spectra. A mechanism for the formation of such unusual structures in ion-implanted silica is proposed. By controlling the implantation energy of the two ions properly and keeping the implantation sequence Ag first and then Au, it is possible to create Au core−Ag shell nanoparticles in the silica matrix with homogeneous distribution.