Nonlinear optical response of platinum nanoparticles and platinum ions embedded in sapphire

Structure Formation and Regulation of Au Nanoparticles in LiTaO3 by Ion Beam and Thermal Annealing Techniques

The size uniformity and spatial dispersion of nanoparticles (NPs) formed by ion implantation must be further improved due to the characteristics of the ion implantation method. Therefore, specific swift heavy ion irradiation and thermal annealing are combined in this work to regulate the size and spatial distributions of embedded Au NPs formed within LiTaO₃ crystals. Experimental results show that small NPs migrate to deeper depths induced by 656 MeV Xe³⁵⁺ ion irradiation. During thermal annealing, the growth of large Au NPs is limited due to the reductions in the number of small Au NPs, and the migrated Au NPs aggregate at deeper depths, resulting in a more uniform size distribution and an increased spatial distribution of Au NPs. The present work presents a novel method to modify the size and spatial distributions of embedded NPs.

Synthesis, Linear and Nonlinear Optical Properties of Ag/Al2O3 Nanocomposites

This work reports a detailed study of the synthesis, characterization and third-order nonlinear optical properties of Ag and Al₂O₃ nanoparticles and their polymer nanocomposites. Ag and Al₂O₃ nanoparticles were prepared by the chemical precipitation method. The X-ray diffraction studies confirmed the purity and the crystalline nature of the sample and revealed the crystallite size. The linear optical properties and the structural morphology of the nanoparticles were confirmed using UV-visible spectroscopy and SEM analysis. The prepared nanoparticles were introduced into the polymer matrix by the spin-coating technique. Open-aperture and closed-aperture Z-scan technique was used to study the nonlinear absorption and nonlinear refraction of the samples under a Q-switched Nd:YAG laser at 532 nm. The observed third-order nonlinear optical susceptibility (χ⁽³⁾) was on the order of 10^-6 esu, which indicates that these materials are potential candidates for photonic applications.

Controlled Synthesis of Platinum and Silver Nanoparticles Using Multivalent Ligands

Here, the controlled formation of platinum nanoparticles (PtNPs) and silver nanoparticles (AgNPs) using amine-functionalized multivalent ligands are reported. The effects of reaction temperature and ligand multivalency on the growth kinetics, size, and shape of PtNPs and AgNPs were systematically studied by performing a stepwise and a one-step process. PtNPs and AgNPs were prepared in the presence of amine ligands using platinum (II) acetylacetonate and silver (I) acetylacetonate, respectively. The effects of ligands and temperature on the formation of PtNPs were studied using a transmission electron microscope (TEM). For the characterization of AgNPs, additionally, ultraviolet-visible (UV-Vis) absorption was employed. The TEM measurements revealed that PtNPs prepared at different temperatures (160–200 °C, in a stepwise process) are monodispersed and of spherical shape regardless of the ligand multivalency or reaction temperature. In the preparation of PtNPs by the one-step process, ligands affect the shape of the PtNPs, which can be explained by the affinity of the ligands. The TEM and UV-Vis absorption studies on the formation of AgNPs with mono-, di-, and trivalent ligands showed narrower size distributions, while increasing the temperature from 80 °C to 120 °C and with a trivalent ligand in a one-step process.

Third-order nonlinear optical properties of a multi-layer Al2O3/ZnO for nonlinear optical waveguides

This is a report of a study of the nonlinear optical properties of samples based on multiple Al₂O₃/ZnO bilayers fabricated by atomic layer deposition (ALD) in silica. The multi-layer configuration for samples consists of alternated layers of constant thickness of Al₂O₃ (Δx) and ZnO (Δy) nanolaminates with a total thickness of ∼ 500 nm. The physical properties of the samples were characterized by means of TEM, spectrophotometry and variable angle spectroscopic ellipsometry. The absorptive and refractive contributions to the nonlinearity of the samples were studied by means of z-scan technique using a 100 fs at 800 nm. The nonlinear parameters, β and n₂, are studied using different values of the layers thickness, Δx and Δy, in the nanolaminated stack. The possible applications in optical signal processing system are discussed by means of the figures of merit W and T.

Laser-induced electrical signal filtering by multilayer reduced graphene oxide decorated with Au nanoparticles

Nanoscale plasmonic particles represent a crucial transformation on optical and electronic properties exhibited by advanced materials. Herein are reported remarkable interferometric optical effects with dependence on polarization for filtering or modulating electronic signals in multilayer nanostructures. Metallic nanoparticles were incorporated in randomly distributed networks of reduced graphene oxide by an in-situ vapor-phase deposition method. The polarization-selectable nonlinear optical absorption contribution on the photoconductivity of reduced graphene oxide decorated with gold nanoparticles was analyzed. Nanosecond pulses at 532 nm wavelength were employed in a two-wave mixing experiment to study photoconduction and nonlinear optical absorption in this nanohybrid material. The ablation threshold of the sample was measured in 0.4 J/cm². Electrochemical impedance spectroscopy measurements revealed a capacitive response that can be enhanced by gold decoration in carbon nanostructures. A strong two-photon absorption process characterized by 5 × 10^-7 m/W was identified as a physical mechanism responsible for the nonlinear photoconductive behavior of the nanostructures. Experimental shift of 1 MHz for the cutoff frequency associated with an electrical filter function performed by the sample in film form was demonstrated. Moreover, amplitude modulation of electronic signals controlled by the polarization of a two-wave mixing experiment was proposed. All-optical and optoelectronic nanosystems controlled by multi-photonic interactions in carbon-based materials were discussed. The key role of the vectorial nature of light in two-wave mixing experiments is a fascinating tool for the exploration of low-dimensional systems.

Structural and Optical Properties Correlated with the Morphology of Gold Nanoparticles Embedded in Synthetic Sapphire: A Microscopy Study

This work reports on the electron microscopy analysis of the structure and morphology of gold nanoparticles produced by ion implantation as well as their relationship to their optical properties. Metalic nanoparticles by ion implantation are usually spherical and formed beneath the surface of a dielectric matrix. In this experiment, the matrix was sapphire. After high-energy Si ion irradiation, the gold nanoparticles were elongated into prolate spheroids. Since the nanoparticles are embedded in a dielectric matrix, secondary electron imaging in a JEOL JSM-7800F at low voltage did not allow their analysis. This work proposes an analysis using backscattered electron imaging in a field emission scanning electron microscopy at higher voltages (20 kV) to explore the morphology of the embedded nanoparticles. The samples were observed by cross-sectional view as well as a top view of the surface of the sapphire matrix for exploration and recognition of their morphology, dimensions, distribution, and composition. The analysis was extended by means of Rutherford backscattering spectrometry, X-ray diffraction, and optical extinction spectroscopy. The nanoparticles exhibited structural and optical properties correlated directly to the morphology observed by microscopy. The beam interaction with the sample and the used parameters was simulated in the CASINO code, from which the depth of exploration with distinct parameters used in microscopy analysis was estimated.

Nonlinear Absorption Response Correlated to Embedded Ag Nanoparticles in BGO Single Crystal: From Two-Photon to Three-Photon Absorption

We report on the embedded silver (Ag) nanoparticles fabricated by Ag+ ion implantation into the Bi4Ge3O12 (BGO) crystal. Localized surface plasmon resonance (LSPR) phenomenon has been observed by linear optical absorption spectrum, which is accordance with the expectation based on Mie theory calculation. Further proofs are given by SRIM, TEM and SAED analysis, which explain the slight difference between experiment and calculation. Based on the z-scan system, it is found that the nonlinear optical response is converted from two-photon absorption to three-photon absorption under the 515 nm femtosecond pulse excitation within the LSPR band. The nonlinear absorption coefficient is measured to be ~3.1 × 10-9 cm/W (two-photon absorption coefficient) and ~8.9 × 10-14cm3/W2 (three-photon absorption coefficient) for pure BGO crystal and the sample embedded with Ag nanoparticles (Ag:BGO), respectively. Finally, we have proposed a model to explain the asymmetric nonlinear transmittance, which is in good agreement with the experimental results.

Giant Enhancement of Nonlinear Optical Response in Nd:YAG Single Crystals by Embedded Silver Nanoparticles

We report on the enhancement and modulation of nonlinear optical response in an Nd:Y₃Al₅O₁₂ (Nd:YAG) laser crystal through embedded silver nanoparticles (NPs) fabricated by Ag⁺ ion implantation. The linear absorption spectrum of the sample clearly reveals a localized surface plasmon resonance (SPR) band from 350 to 700 nm correlated to the Ag NPs. By using the Z-scan technique with femtosecond pulses at a wavelength of 515 nm, which is considered as an optical excitation within the SPR band, the nonlinear refraction index reaches values as high as ∼10^-12 cm²/W, enhanced by ∼4 orders of magnitude in comparison to that of unimplanted Nd:YAG (without Ag NPs). In addition, it has been shown that embedded Ag NPs in the Nd:YAG host reveal saturable absorption signifying the nonlinear responses. We have also observed that the nonlinear absorption coefficients depend significantly on the excitation energy and can be modulated by varying the fluence of Ag⁺ ions.

Nonlinear optical properties of metal nanoparticles: a review

Metal nanoparticles (MNPs) hold great technological promise because of the possibility of engineering their electronic and optical properties through material design.

Nonlinear optical response of platinum nanostructures and application for water detection in transformer oil

We report the fabrication of platinum nanostructures on an ITO substrate (Pt-NSs).