Elimination of bleaching in a material based on aqueous fluid with carbon nanoparticles for optical limiters

The possibilities of correcting the functional properties of nonlinear optical limiters based on carbon nanoparticles using polymer dopants have been considered. The results of analyzing the characteristics of nonlinear optical limiting of a suspension of carbon black with addition of sodium dodecylbenzene sulfonate and polyvinyl alcohol are given. The forms in which particles exist in the suspension have been investigated by different physicochemical methods. Optical measurements have confirmed the efficiency of these additives.     

A review of characterization and physical property studies of metallic nanoparticles

In this survey, the characterization of metallic nanoparticles prepared by various methods and the physical properties including the theory and measurements of linear and nonlinear optics, electric and magnetic properties are reviewed. Technical results involving linear optical absorption, optical second harmonic generation, temperature dependence of resistivity, electron paramagnetic resonance and magnetic susceptibility measurements were portrayed. A number of fascinating and provocative results have been developed that lead our perspective understanding of quantum size confinements.     

Ultrafast nonlinear spectroscopy of a single silver nanoparticle

The time‐domain nonlinear spectroscopy of a single silver nano‐object is investigated by combining the spatial modulation linear spectroscopy technique with a high‐sensitivity femtosecond pump–probe setup. The investigated single nanoparticle is first optically characterized for size and shape via quantitative measurement of its linear absorption spectrum, and time‐resolved nonlinear pump‐probe measurements are subsequently performed on the same particle. The breathing mode period of a single nanoparticle measured in the time domain is found to be in good agreement with that inferred by the optically deduced particle characteristics, opening the way of full optical investigation of the acoustic response of the characterized single nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd.     

Broadband optical limiting in the suspensions of lead sulfide nanoparticles

Nanoparticles of lead sulfide (PbS) have been prepared by a surfactant micelle template-inducing reaction. These nanoparticles were dispersed in ethanol and investigated for their nonlinear optical properties by nanosecond laser pulses. Broadband optical limiting effects have been observed at the wavelengths of 355, 1064, and 430 nm and every 30 nm from 470 to 620 nm. The nonlinear light-scattering process in the suspensions of PbS nanoparticles was characterized at the wavelength of 532 nm. Nonlinear absorption and nonlinear scattering were deduced to be the mechanisms for the broadband optical limiting performance. The origins of the nonlinear scattering were discussed.     

Blue-shifted plasmon resonance of individual size-selected gold nanoparticles

The future implementation of integrated photonic devices requires the creation of nanostructures with well defined morphological and optical properties. To this end, we deposited size-selected gold nanoparticles produced by a gas phase aggregation cluster source on transparent substrates at room temperature with controlled impact energy. Interferometric optical detection measurements using a supercontinuum laser source demonstrated a blue-shifted plasmon resonance at the single particle level. The blue shift was observed to be more pronounced for small single clusters down to 3 nm in size.     

Time-resolved analysis of nonlinear optical limiting for laser synthesized carbon nanoparticles

Nonlinear optical limiting materials have attracted much research interest in recent years. Carbon nanoparticles suspended in liquids show a strong nonlinear optical limiting function. It is important to investigate the nonlinear optical limiting process of carbon nanoparticles for further improving their nonlinear optical limiting performance. In this study, carbon nanoparticles were prepared by laser ablation of a carbon target in tetrahydrofuran (THF). Optical limiting properties of the samples were studied with 532-nm laser light, which is in the most sensitive wavelength band for human eyes. The shape of the laser pulse plays an important role for initializing the nonlinear optical limiting effect. Time-resolved analysis of laser pulses discovered 3 fluence stages of optical limiting. Theoretical simulation indicates that the optical limiting is initialized by a near-field optical enhancement effect.     

Optical properties of one-dimensional soft photonic crystals with ferrofluids

We review the recent theoretical study on the optical properties of one-dimensional soft photonic crystals (1D SPCs) with ferrofluids. The proposed structure is composed of alternating ferrofluid layers and dielectric layers. For the ferrofluid, single domain ferromagnetic nanoparticles can align to a chain under the stimuli of an external magnetic field, thus changing the microstructure of the system. Meanwhile, nonlinear optical responses in ferrofluids are also briefly reviewed.     

Glutathione-capped core-shell structured magnetite nanoparticles: Fabrication and their nonlinear optical characteristics

Core-shell structured magnetic Fe₃O₄@glutathione composite nanoparticles were synthesized and examined using diverse methods including Fourier-transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray analysis, transmission electron microscope, thermogravimetric analysis, and vibrating sample magnetometer analysis. In addition, the nonlinear optical measurements were performed by both open and closed aperture z-scan methods using an aqueous colloidal solution of the fabricated nanoparticles. The colloidal system exhibited a positive nonlinear refractive index because of the self-focusing effect arising from optical re-orientation. Although optical re-orientation is a rare phenomenon in nanocolloids, high polarizability of the enveloping organic ligands caused optical re-orientation of the composite nanoparticles in the electrical field direction of the incident beam. Finally, the effect of external voltage on the nonlinear optical index was further investigated.     

Formation, structure and nonlinear optical properties of carbon nanoparticles synthesized by pulsed laser ablation

Carbon nanoparticles were prepared by pulsed laser ablation in argon gas for studying their formation, properties and applications. The nanoparticles were produced at different background pressures and different substrate temperatures, respectively. Micro-Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the samples. Nonlinear optical limiting properties of the carbon nanoparticles were characterized using nanosecond laser pulses. Uniform carbon nanoparticles can be synthesized in a background gas for nonlinear optical applications. PACS 61.46.+w; 81.07.-b; 78.20.-e     

Gyroscopic behavior exhibited by the optical Kerr effect in bimetallic Au–Pt nanoparticles suspended in ethanol

The modification in the third-order nonlinear optical response exhibited by rotating bimetallic Au–Pt nanoparticles in an ethanol solution was analyzed. The samples were prepared by a sol–gel processing route. The anisotropy associated to the elemental composition of the nanoparticles was confirmed by high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy measurements. The size of the nanoparticles varies in the range from 9 to 13 nm, with an average size of 11 nm. Changes in the spatial orientation of the nanomaterials automatically generated a variation in their plasmonic response evaluated by UV–Vis spectroscopy. A two-wave mixing experiment was conducted to explore an induced birefringence at 532 nm wavelength with nanosecond pulses interacting with the samples. A strong optical Kerr effect was identified to be the main responsible effect for the third-order nonlinear optical phenomenon exhibited by the nanoparticles. It was estimated that the rotation of inhomogeneous nanostructures can provide a remarkable change in the participation of different surface plasmon resonances, if they correspond to multimetallic nanoparticles. Potential applications for developing low-dimensional gyroscopic systems can be contemplated.     

Evolution of terahertz conductivity in ZnSe nanocrystal investigated with optical-pump terahertz-probe spectroscopy

The unique optical properties of nanoparticles are highly sensitive in respect to particle shapes, sizes, and localization on a sample. This demands for a fully controlled fabrication process. The use of femtosecond laser pulses to generate and transfer nanoparticles from a bulk target towards a collector substrate is a promising approach. This process allows a controlled fabrication of spherical nanoparticles with a very smooth surface. Several process parameters can be varied to achieve the desired nanoparticle characteristics. In this paper, the influence of two of these parameters, i.e. the applied pulse energy and the laser beam shape, on the generation of Si nanoparticles from a bulk Si target are studied in detail. By changing the laser intensity distribution on the target surface one can influence the dynamics of molten material inducing its flow to the edges or to the center of the focal spot. Due to this dynamics of molten material, a single femtosecond laser pulse with a Gaussian beam shape generates multiple spherical nanoparticles from a bulk Si target. The statistical properties of this process, with respect to number of generated nanoparticles and laser pulse energy are investigated. We demonstrate for the first time that a ring-shaped intensity distribution on the target surface results in the generation of a single silicon nanoparticle with a controllable size. Furthermore, the generated silicon nanoparticles presented in this paper show strong electric and magnetic dipole resonances in the visible and near-infrared spectral range. Theoretical simulations as well as optical scattering measurements of single silicon nanoparticles are discussed and compared.     

Diffraction patterns and nonlinear optical properties of gold nanoparticles

Stable gold nanoparticles have been prepared by using soluble starch as both the reducing and stabilizing agents; this reaction was carried out at 40 °C for 5 h. The obtained gold nanoparticles were characterized by UV–Vis absorption spectroscopy, transmission electron microscopy (TEM) and z-scan technique. The size of these nanoparticles was found to be in the range of 12–22 nm as analyzed using transmission electron micrographs. The optical properties of gold nanoparticles have been measured showing the surface plasmon resonance. The second-order nonlinear optical (NLO) properties were investigated by using a continuous-wave (CW) He–Ne laser beam with a wavelength of 632.8 nm at three different incident intensities by means of single beam techniques. The nonlinear refractive indices of gold nanoparticles were obtained from close aperture z-scan in order of 10^?7 cm²/W. Then, they were compared with diffraction patterns observed in far-field. The nonlinear absorption of these nanoparticles was obtained from open aperture z-scan technique. The values of nonlinear absorption coefficient are obtained in order of 10^?1 cm/W.     

Investigation of the nonlinear optical characteristics of composite materials based on sapphire with silver, copper, and gold nanoparticles by the reflection Z-scan method

The nonlinear optical characteristics of silver, copper, and gold nanoparticles synthesized in a sapphire matrix by ion implantation are studied. The measurements are performed by the RZ-scan method with optical reflection at the radiation wavelength of a picosecond Nd:YAG laser (λ = 1064 nm). The nonlinear refractive indices and the real parts of the third-order nonlinear susceptibility of the composites are determined. It is shown that the nonlinear refraction in the samples is caused by the Kerr effect.     

Third-order nonlinear optical properties of graphene composites: A review

Graphene has excellent thirdorder nonlinear optical (NLO) properties due to its unique electronic band structure and wideband gap tunability. This paper focuses on the research progress of graphene and its composite materials in nonlinear optics in recent years. In this review, recent results on graphene (or graphene oxide)-metal nanoparticles (G-MNPs), graphene-metal-oxide nanoparticles (G-MONPs), graphene-metal sulfide nanoparticles (G-MSNPs), and graphene-organic molecular composites (G-OM) have been discussed. In addition, the enhancement mechanism of nonlinear absorption (NLA) and optical limiting (OL) have also been covered.     

Laser ablation of GaAs in liquids: structural, optical, and nonlinear optical characteristics of colloidal solutions

We investigated the optical, structural, and nonlinear optical properties of GaAs nanoparticles prepared by laser ablation in various liquids at the wavelengths of 795 nm and 1,054 nm. The slow-thermal-effect-induced self-defocusing processes were dominating both in the cases of high pulse repetition rate and nanosecond pulses. The two-photon absorption was observed in these colloidal solutions in the case of low pulse repetition rate of picosecond and femtosecond radiation. The nonlinear susceptibility of GaAs nanoparticles ablated in water was measured to be 2× 10^–9 esu.     

Effect of Ag Nanoparticles on Optical Properties of R6G Doped PMMA Films

The composite PMMA films containing Ag nanoparticles and rhodamine 6G are prepared. We investigate the fluorescence properties and nonlinear optical properties of R6G/PMMA films influenced by Ag nanoparticles. The fluorescence enhancement factor is about 3.3. The corresponding nonlinear refractive index is measured to be -2.423 ×10^-8 esu using the Z-scan technique, which is much enhanced compared with the R6G/PMMA film. The results indicate that these enhancements are attributed to surface plasmon resonance of Ag nanoparticles.     

Characterization of optical and nonlinear optical properties of silver nanoparticles prepared by laser ablation in various liquids

The optical, structural, and nonlinear optical properties of silver nanoparticles prepared by laser ablation in various liquids were investigated at 397.5, 532, and 795 nm. The TEM and spectral measurements have shown temporal dynamics of size distribution of Ag nanoparticles in solutions. The thermal-induced self-defocusing dominated in the case of high pulse repetition rate as well as in the case of nanosecond pulses. In the case of low pulse repetition rate, the self-focusing (γ = 3 × 10⁻¹³ cm² W⁻¹) and saturated absorption (β = −1.5 × 10⁻⁹ cm W⁻¹) of picosecond and femtosecond radiation were observed in these colloidal solutions. The nonlinear susceptibility of Ag nanoparticles ablated in water was measured to be 5 × 10⁻⁸ esu (at λ = 397.5 nm).     

Opto-acoustic sensing of fluids and bioparticles with optomechanofluidic resonators

Opto-mechano-fluidic resonators (OMFRs) are a unique optofluidics platform that can measure the acoustic properties of fluids and bioanalytes in a fully-contained microfluidic system. By confining light in ultra-high-Q whispering gallery modes of OMFRs, optical forces such as radiation pressure and electrostriction can be used to actuate and sense structural mechanical vibrations spanning MHz to GHz frequencies. These vibrations are hybrid fluid-shell modes that entrain any bioanalyte present inside. As a result, bioanalytes can now reflect their acoustic properties on the optomechanical vibrational spectrum of the device, in addition to optical property measurements with existing optofluidics techniques. In this work, we investigate acoustic sensing capabilities of OMFRs using computational eigenfrequency analysis. We analyze the OMFR eigenfrequency sensitivity to bulk fluid-phase materials as well as nanoparticles, and propose methods to extract multiple acoustic parameters from multiple vibrational modes. The new informational degrees-of-freedom provided by such opto-acoustic measurements could lead to surprising new sensor applications in the near future.     

Growth and characterization of an efficient nonlinear optical single crystal: Urea p-nitrophenol

An organic nonlinear optical single crystal of urea p-nitrophenol has been synthesized and grown by slow evaporation solution growth technique. The grown crystals were characterized by single crystal and powder X-ray diffraction analysis and it was found to be the structure of the crystal belongs to triclinic system. The various functional groups were identified by FT-IR and Raman spectral analysis. Thermal stability of the grown crystal was studied by TGA/DTA. The optical properties of the grown crystals were analyzed by UV–vis. The mechanical properties of the grown crystal were studied by Vickers microhardness measurements. Nonlinear optical property of the crystal was confirmed using the Kurtz and Perry powder technique and a study of its SHG efficiency in comparison with KDP has made.     

Third-order nonlinear optical properties of silver nanoparticles mediated by chitosan

Silver nanoparticles in chitosan medium were prepared by the chemical reduction method. Silver nitrate and hydrazine were used as the precursor and reducing agent in the present of chitosan as a natural host polymer. The samples are characterized by UV–visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The measurements of nonlinear optical properties were defined by Z-scan technique using green CW laser beam operated at 532 nm wavelengths. Thermal effect has a dominant role in the overall material nonlinearity with CW laser. It is shown that the synthesized samples have a negative nonlinear refractive index.