Wavelength-Dependent Optical Nonlinear Absorption of Au-Ag Nanoparticles

The nonlinear optical absorption properties of Au-Ag nanoparticles (NPs) were studied using an open-aperture Z-scan under a nanosecond pulsed laser with wavelengths of 450 nm, 510 nm, 550 nm, and 600 nm. The experimental results demonstrated that, when the laser intensity was 1.04 × 1013 W/m2, the Au-Ag NPs showed saturated absorption (SA). When the laser intensity was increased to 3.03 × 1013 W/m2, the switch from SA to reverse saturation absorption (RSA) occurred. The nonlinear absorption and its transformation were analyzed by using local surface plasmon resonance (LSPR) effect, bleaching of ground state plasmon, and free carrier absorption theory.

Tuning the Non-Linear Optical Absorption Properties of Eu3+ Doped NiWO4 Nanostructures

NiWO4 nanostructures doped with different ratios of Eu3+ have been prepared by a chemical precipitation method. The influence of Eu3+ on NiWO4 nanostructures were characterized using X-ray diffraction (XRD), UV-visible diffuse reflectance spectra, scanning electron microscopy (SEM) and Raman. XRD patterns display that the samples crystallize to monoclinic wolframite structure. SEM images reveal that the particles are well uniformly dispersed with average particle size lies around 40-50nm. Third-order nonlinear optical properties were studied by a Z-scan technique at 532 nm using continuous wave diode pumped Nd:YAG laser. Open and closed aperture results reveal the nanostructures to possess reverse saturation absorption and negative nonlinear refraction. The calculated absorption coefficients (β), imaginary part of third-order susceptibilities Imχ(3) are in the order of 10-6(cm/W) and 10-7 esu. These results indicated that the synthesized nanostructures could be promising materials for optical device applications.

SOME ASPECTS OF THE MATERIALS’ OPTICAL LIMITING FEATURES

Due to the effective use of the fullerenes and other nanoparticles in the materials for the general optoelectronic, laser and display technique, as well as for biomedicine, the different mechanisms to attenuate the light intensity are considered with good advantage in order to protect the human eyes and technical devises from high laser irradiation. Reverse saturation absorption, complex formation, scattering, etc. are taken into account. In the current paper the influence of the content of the nanoobjects on the interface relief is shown and considered as an additional possible optical limiting mechanism. Moreover, the diffraction from the nanostructured materials via high frequency Kerr effect is added to extend the numbers of the optical limiting mechanisms. Different experimental instruments and supporting models are presented. VIS lasers, AFM, OCA devises are applied to test and visualize the results. Theoretical and experimental data are in good coincidence.

Nonlinear Optical Characteristics of Crystal VioletDye Doped Polystyrene Films by Using Z-Scan Technique

Z-scan technique was employed to study the nonlinear optical properties (nonlinear refractive index and nonlinear absorption coefficient) for crystal violet doped polystyrene films as a function of doping ratio in chloroform solvent. Samples exhibits in closed aperture Z-scan positive nonlinear refraction (self-focusing). While in the open aperture Z-scan gives reverse saturation absorption (RSA) (positive absorption) for all film with different doping ratio making samples candidates for optical limiting devices for protection of sensors and eyes from energetic laser light pulses under the experimental conditions.

CW Optical Limiting Study in Disperse Yellow Dye-doped PMMA-MA Polymer Films

<div><p><em>Molecules with high two-photon absorption (TPA) cross section and the molecules which have reverse saturation absorption (RSA) cross section are of great interest today because of their application in three-dimensional optical data storage and photonic switches. During last forty years, several techniques have been developed to determine the two-photon absorption cross-sections and reverse saturation absorption cross-sections of the materials. This includes direct methods, such as nonlinear transmission and Z-scan methods and indirect methods, such as two-photon excited fluorescence and two-photon pump-probe transient absorption spectroscopy. During recent years, the organic dye-doped polymer films getting more attention due to their advantages to fabricate photonics devices. In this paper, we have studied the nonlinear optical properties like nonlinear absorption and nonlinear refraction of an azo dye Disperse yellow-7 (DY-7) doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix using open aperture and closed aperture Z-scan experimental methods using continuous wave (CW) laser. The optical limiting properties of these films are also studied in Type 1 and Type 2 configurations at different input power using continuous wave (CW) laser beams of 532 nm wavelength.</em></p></div>

Study of molecular aggregation effects on the nonlinear refractive index and absorption of Oxazin 720 laser dye

In this experimental work, nonlinear optical properties of Oxazine 720 laser dye in acetone, dimethyl sulfoxide, ethanol, and water were studied using the z-scan method. It is found that the nonlinear behavior of Oxazine 720 dye in water is different from other organic solvents. The magnitude of the nonlinear refractive index was obtained in the order of 10−8 and 10−7 cm2/W for the 0.2 mmol/L solutions of this dye in water and other solvents, respectively. Also, it was observed that, in the aqueous solution, reverse saturation absorption occurs while, in other organic solvents, saturation absorption occurs and, near the focal point of the lens, it is converted to reverse saturation absorption. These differences in the nonlinear refractive index and nonlinear absorption changes of aqueous solution and other solutions may be due to strong aggregative behavior of dye molecules in water.