Search

With the miniaturization of electronic-based devices, the foreseen potential of new optical nanoprobes and the assessment of eventual size and shape effects, elaboration of multifunctional noncentrosymmetric nanocrystals with ferroelectric, pyroelectric, piezoelectric, and nonlinear optical properties are the subject of an increasing research interest. Here, the recent achievements from the solution-based methods (coprecipitation in homogeneous and nanostructured media, sol-gel processes including various chemistries and hydro/solvothermal techniques) to prepare 0-D perovskite and nonperovskite oxides in the 5-500 nm size range are critically reviewed. To cover a representative list of covalent- and ionic-type materials, BaTiO

Pure α-La(IO3)3 and α-La0.85Er0.15(IO3)3 nanocrystals were synthesized by a microwave-assisted hydrothermal method leading to a reaction yield of 87 ± 4%. Electron microscopy and dynamic light scattering characterizations provide evidence for the formation of nanocrystals with an average size of 45 ± 10 nm for α-La(IO3)3 and 55 ± 10 nm for α-La0.85Er0.15(IO3)3. When dispersed in ethylene glycol, the nanocrystal suspensions exhibit second-harmonic generation under near-infrared excitations at 800 and 980 nm whereas additional photoluminescence by up-conversion is simultaneously observed in the case of α-La0.85Er0.15(IO3)3 nanocrystals. Quantitative assessments of the second-harmonic generation efficiency from second-harmonic scattering experiments at 1064 nm result in relatively high ⟨ d⟩ coefficients measured at 8.2 ± 2.0 and 8.0 ± 2.0 pm V-1 for α-La(IO3)3 and α-La0.85Er0.15(IO3)3, respectively. The relative intensity between second-harmonic generation and photoluminescence is discussed following the excitation wavelength.

Hybrid nanoparticles composed of an efficient nonlinear optical core and a gold shell can enhance and tune the nonlinear optical emission thanks to the plasmonic effect. However the influence of an incomplete gold shell, i.e., isolated gold nano-islands, is still not well studied. Here LiNbO3 (LN) core nanoparticles of 45 nm were coated with various densities of gold nano-seeds (AuSeeds). As both LN and AuSeeds bear negative surface charge, a positively-charged polymer was first coated onto LN. The number of polymer chains per LN was evaluated at 1210 by XPS and confirmed by fluorescence titration. Then, the surface coverage percentage of AuSeeds onto LN was estimated to a maximum of 30% using ICP-AES. The addition of AuSeeds was also accompanied with surface charge reversal, the negative charge increasing with the higher amount of AuSeeds. Finally, the first hyperpolarizability decreased with the increase of AuSeeds density while depolarization values for Au-seeded LN were close to the one of bare LN, showing a predominance of the second harmonic volumic contribution. ispartof: NANOMATERIALS vol:11 issue:4 ispartof: location:Switzerland status: published

Phase-pure, highly crystalline sub-50 nm LiNbO3 nanocrystals were prepared from a non-aqueous solvothermal process for 72 h at 230 &deg, C and a commercial precursor solution of mixed lithium niobium ethoxide in its parent alcohol. A systematic variation of the reaction medium composition with the addition of different amounts of co-solvent including butanol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol resulted in the formation of nanocrystals of adjustable mean size and shape anisotropy, as demonstrated from XRD measurements and TEM imaging. Colloidal stability of ethanol- and water-based suspensions was evaluated from dynamic light scattering (DLS)/zeta potential studies and correlated with FTIR data. Thanks to the evolution in the nanocrystal size and shape distribution we observed, as well as to the available literature on the alkoxide chemistry, the reaction pathways and growth mechanisms were finally discussed with a special attention on the monomer formation rate, leading to the nucleation step. The polar, non-perovskite crystalline structure of LiNbO3 was also evidenced to play a major role in the nanocrystal shape anisotropy.

International audience; Whereas most of the reports on the nonlinear properties of micro- and nanostructures address the generation of distinct signals, such as second or third harmonic, here we demonstrate that the novel generation of dual output lasers recently developed for microscopy can readily increase the accessible parameter space and enable the simultaneous excitation and detection of multiple emission orders such as several harmonics and signals stemming from various sum and difference frequency mixing processes. This rich response, which in our case features 10 distinct emissions and encompasses the whole spectral range from the deep ultraviolet to the short-wave infrared region, is demonstrated using various nonlinear oxide nanomaterials while being characterized and simulated temporally and spectrally. Notably, we show that the response is conserved when the particles are embedded in biological media opening the way to novel biolabeling and phototriggering strategies.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

International audience; We report the microwave-assisted hydrothermal synthesis of α-La(IO3)3 nanocrystals doped with Yb 3+ and Er 3+ ions, along with their structural and optical characterizations. 50-nm sized α-La0.9-xYb0.1Erx(IO3)3 nanocrystals with x = 0.005, 0.01 and 0.02 were synthesized and dispersed in ethylene glycol. The as-obtained suspensions exhibit both Second Harmonic Generation (SHG) signal and up-conversion photoluminescence (UC-PL) without interplay between the two signals under near-infrared resonant excitation. The relative intensity of SHG and UC-PL emission can be modulated according to the excitation wavelength. The most intense UC-PL signal is obtained from a 980-nm excitation, thanks to the sensitization of Er 3+ by Yb 3+. 2

The design of stimuli-responsive nanocarriers has raised much attention to achieve higher local concentration of therapeutics and mitigate the appearance of drug resistance. The combination of imaging properties and controlled photorelease of active molecules within the same nanoconjugate has a great potential for theranostic applications. In this study, a system for NIR light-triggered release of molecular cargos induced by the second harmonic emission from bismuth ferrite harmonic nanoparticles (BFO HNPs) is presented. Silica-coated BFO HNPs were covalently conjugated to a photocaging tether based on coumarin (CM) and l-tryptophan (Trp) as a model molecular cargo. Upon femtosecond pulsed irradiation at 790 nm, Trp was efficiently released from the NP surface in response to the harmonic emission of the nanomaterial at 395 nm. The emitted signal induced the photocleavage of the CM-Trp carbamate linkage resulting in the release of Trp, which was monitored and quantified by ultrahigh performance liquid chromatography-mass spectrometry (UHPLC-MS). While a small fraction of the uncaging process could be attributed to the nonlinear absorption of CM derivatives, the main trigger responsible for Trp release was established as the second harmonic signal from BFO HNPs. This strategy may provide a new way for the application of functionalized HNPs in dual imaging delivery theranostic protocols.

Pure α-La(IO

Preparation of stable BiFeO3 nanocrystal suspensions through a simple, low-cost precipitation technique is described. Amorphous precursors are first precipitated from metal nitrate salts in highly basic KOH solutions, and a short high-temperature annealing step is then performed to induce crystallization. Nanoparticles are characterized by X-ray diffraction (XRD), TEM, DLS and ζ-potential measurements, and the synthesis conditions optimized after a systematic variation of the KOH concentration within the range of 1–12 M. The presence of residual impurities (mainly Bi25FeO39 and Bi2Fe4O9) quantified from XRD and mean nanocrystal size is found to be strongly influenced by the initial KOH solution content. A concentration at about 3–4 M is optimal in terms of BiFeO3 phase-purity and nanocrystal size. Stability of aqueous dispersions of the amorphous precursors and of the purest crystallized nanoparticles is also characterized between pH = 2 and pH = 13. After preparation of stable, almost phase-pure BiFeO3 nanocrystal suspensions, second and third harmonic scattering (SHS and THS) at excitation wavelengths of 1064 nm and 1250 nm are reported from nonlinear optical scattering measurements and compared with other recently published literature values.

We demonstrate the simultaneous generation of second, third, and fourth harmonic from a single dielectric Bismuth Ferrite nanoparticle excited by a telecom fiber laser at 1560 nm. We first characterize the signals associated with different nonlinear orders in terms of spectrum, excitation intensity dependence, and relative signal strengths. Successively, on the basis of the polarization-resolved emission curves of the three harmonics, we discuss the interplay of susceptibility tensor components at the different orders and we show how polarization can be used as an optical handle to control the relative frequency conversion properties., Comment: include S.I. section at the end of the main pdf file

A tunable wavelength Hyper Rayleigh Scattering setup was developed to assess and compare Second Harmonic Scattering from Lithium Niobate, Zinc Oxide and Bismuth Ferrite nanocrystal suspensions in the 730–1150 nm excitation range.

We demonstrate the simultaneous generation of more than four harmonics from individual dielectric nanoparticles excited by a telecom fiber laser at 1560. We discuss the possibility to control their relative intensities by the laser polarization.

International audience

We present two new synthetic routes for bismuth ferrite harmonic nanoparticles (BiFeO3 HNPs). Both phase-pure and mixed phase BiFeO3 materials were produced after improvement of the solvent evaporation and sol-gel combustion routes. Metal nitrates with a series of dicarboxylic acids (tartronic, tartaric and mucic) were used to promote crystallization. We found that the longer the carbon backbone with a hydroxyl group attached to each carbon, the lower the annealing temperature. We also demonstrate that nanocrystals more readily formed at a given temperature by adding glycerol but to the detriment of phase purity, whereas addition of NaCl in excess with mucic acid promotes the formation of phase-pure, monocrystalline nanoparticles. This effect was possibly associated with a better dispersion of the primary amorphous precursors and formation of intermediate complexes. The nanoparticles have been characterized by XRD, TEM, ζ-potential, photon correlation spectroscopy, two-photon microscopy and Hyper-Rayleigh Scattering measurements. The improved crystallization leads to BiFeO3 HNPs without defect-induced luminescence and with a very high averaged second harmonic efficiency (220 pm/V), almost triple the efficiency previously reported. This development of simple, scalable synthesis routes which yield phase-pure and, crucially, monocrystalline BiFeO3 HNPs demonstrates a significant advance in engineering the properties of nanocrystals for bio-imaging and diagnostics applications.

Hyper Rayleigh scattering (HRS) was used to measure the second-order nonlinear susceptibility, χ

Polymethyl methacrylate (PMMA)/Fe(IO3)3 nanocomposite thin films are obtained by in situ particle generation in microemulsions and subsequent photopolymerization of a mixture containing methyl methacrylate, trimethylolpropane triacrylate, and crystallized iron iodate (Fe(IO3)3) nanorods. Hyper-Rayleigh scattering measurements combined with X-ray diffraction, transmission electron microscopy, and dynamic light scattering are first used to probe in situ the crystallization kinetics of iron iodate nanorods in water-in-oil microemulsions prepared with methyl methacrylate as the oil phase and marlophen NP12 as a surfactant. Trimethylolpropane triacrylate is then added as a crosslinker before spin-coating. Films are deposited on glass substrates for the nonlinear optical characterizations and on silicon wafers for the piezoelectric and mechanical measurements. Nanocomposite films treated by corona discharge are finally characterized through optical microscopy, laser Doppler vibrometry, and Brillouin spectroscopy. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1203-1211, 2013

Potassium niobate (KNbO3) nanocrystals exhibiting good second harmonic generation properties were coated with dextran derivatives containing primary amine groups. The surface modification results from attractive electrostatic interaction between the aminodextran molecules and the negatively charged surface of bare KNbO3 nanocrystals. To avoid flocculation, a suspension of KNbO3 nanocrystals was firstly prepared and then added drop-wise to an aqueous solution of aminodextran. The as-prepared hybrid (AD-coated KNbO3) nanoparticles were then characterized by using various techniques including transmission electron microscopy (TEM), infrared analysis (FTIR), dynamic light scattering (DLS) and zeta potential measurements as a function of pH of the dispersion medium. Then, the prepared AD- coated KNbO3 nanoparticles were evaluated in vitro diagnostic application as biomarker for non-tumor lung-derived human cells. The obtained results showed that the aminodextran-coated KNbO3 nanoparticles were efficiently bound to the non-tumor lung-derived human cells, which was proved by using a commercial Nikon multi-photon imaging platform. In addition, AD-coated KNbO3 nanoparticles showed good optical contrast for the investigated cells, and consequently they can be efficiently used as contrast agents in the bio-imaging diagnostic domain.

We use Hyper Rayleigh Scattering and polarization resolved multiphoton microscopy to investigate simultaneously the second and third-order nonlinear response of Potassium Niobate and Bismuth Ferrite harmonic nanoparticles. We first derive the second-to-third harmonic intensity ratio for colloidal ensembles and estimate the average third-order efficiency of these two materials. Successively, we explore the orientation dependent tensorial response of individual nanoparticles fixed on a substrate. The multi-order polarization resolved emission curves are globally fitted with an analytical model to retrieve individual elements of susceptibility tensors.

International audience; ABSTRACT: Spherical nanocrystals of iron iodate (Fe(IO3)3) as well as different hierarchically organized hybrid superstructures are synthesized at 80 °C from AOT-based water-in-oil microemulsions. For a fixed reaction time of 2 h, initial addition of PEG molecules and changes in the water/surfactant molar ratio w allow modification of the interactions between surfactant and PEG molecules at the surface of amorphous precursor particles. At low water content (w = 5.8), adsorption of AOT molecules inhibits the formation of crystallized nanoparticles if the amount of added PEG is too low, whereas spherical nanocrystals are obtained otherwise. In contrast, at a high water content (w = 12.2), SEM and TEM imaging reveal that the aggregation-induced crystallization of amorphous precursors induces the formation of higher-order complex forms. Aggregates of elongated cone-shaped bundles of nanofilaments and, subsequently, quasi-spherical urchin-like microstructures as long as the PEG amount is raised are observed. Significantly, lattice parameter refinements originally demonstrate the key role of AOT in the self-assembly and a homogeneous nucleation, leading to the formation of primary bouquet-like structures, is suggested before further self-assembly results in urchinlike structures. In terms of potential applications, spherical nanocrystals are promising exogenous labels for multiphoton microscopy, whereas higher-order architectures give perspectives in the morphogenesis of new functional materials.

Measurements of complex refractive indices n* = n - iκ are performed on pure KTaO 3 and K 0.93 Li 0.07 TaO 3 single crystals by using a spectroscopic ellipsometer in temperature range from room temperature to 10 K. At room temperature, experimentally obtained complex dielectric constants ϵ* = ϵ1−iϵ2 of both crystals are analyzed by the classical Drude model. Temperature dependence of the imaginary part ϵ 2 of K 0.93 Li 0.07 TaO 3 shows a small but distinct change around 70 K. The origin of the anomalous behavior is discussed.

Bismuth Ferrite (BFO) nanoparticles (BFO-NP) display interesting optical (nonlinear response) and magnetic properties which make them amenable for bio-oriented applications as intra- and extra membrane contrast agents. Due to the relatively recent availability of this material in well dispersed nanometric form, its biocompatibility was not known to date. In this study, we present a thorough assessment of the effects of in vitro exposure of human adenocarcinoma (A549), lung squamous carcinoma (NCI-H520), and acute monocytic leukemia (THP-1) cell lines to uncoated and poly(ethylene glycol)-coated BFO-NP in the form of cytotoxicity, haemolytic response and biocompatibility. Our results support the attractiveness of the functional-BFO towards biomedical applications focused on advanced diagnostic imaging., Word Count: 109 Complete Word Count (body text and figure legends) : 4886 Number of Figures: 6 Number of Tables: 0 Number of reference: 45

The present paper presents our work consisting of `doping' SiO2 sol–gel matrices with 5–30% mass of LiIO3 nanocrystals. Indeed, bulk α-LiIO3 is known to be very efficient for second harmonic generation (SHG). Bulk nanocomposite samples have been first studied showing nanocrystallites with size ranging from 50 to 400 nm and SHG. Then dip and spin coating methods have been used to build thin layers. Being given that LiIO3 crystals present structurally a strong dipolar moment, non-linear optical (NLO) properties may be enhanced using Corona discharges to orientate nanocrystals. This paper relates the fabrication process and the structural and optical characterizations of bulk and thin layer material.

Second Harmonic Generation (SHG) from BiFeO3 nanocrystals is investigated for the first time to determine their potential as biomarkers for multiphoton imaging. Nanocrystals are produced by an auto-combustion method with 2-amino-2-hydroxymethyl-propane-1,3-diol as a fuel. Stable colloidal suspensions with mean particle diameters in the range 100–120 nm are then obtained after wet-milling and sonication steps. SHG properties are determined using two complementary experimental techniques, Hyper Rayleigh Scattering and nonlinear polarization microscopy. BiFeO3 shows a very high second harmonic efficiency with an averaged hdi coefficient of 79612 pm/V. From the nonlinear polarization response of individual nanocrystals, relative values of the independent dij coefficients are also determined and compared with recent theoretical and experimental studies. Additionally, the particles show a moderate magnetic response, which is attributed to gamma-Fe2O3 impurities. A combination of high nonlinear optical efficiency and magnetic response within the same particle is of great interest for future bio-imaging and diagnostic applications.

International audience; Aggregation-induced crystallization of iron iodate nanorods within organic-inorganic aggregates of primary amorphous precursors is probed by time-dependent hyper-Rayleigh scattering measurements in Triton X-100 based-microemulsions. In the context of a growing interest of noncentrosymmetric oxide nanomaterials in multi-photon bioimaging, we demonstrate by a combination of X-ray diffraction and electron microscopy that an increase in the synthesis of temperature results in faster crystallization kinetics and in a better shape-control of the final Fe(IO3)(3) nanorods. For initial microemulsions of fixed composition, room-temperature synthesis leads to bundles of 1-3 mu m long nanorods, whereas shorter individual nanorods are obtained when the temperature is increased. Results are interpreted in terms of kinetically unfavorable mesoscale transformations due to the strong binding interactions with Triton molecules. The interplay between the nanorod crystallization kinetics and their corresponding unit cell deformation, evidenced by lattice parameter refinements, is attributed to a temperature-dependent adsorption of surfactants molecules at the organic-inorganic interface.

Proc. SPIE 8611; International audience; In this contribution we present the motivations underlying the introduction of harmonic nanoparticles, i.e. Second harmonic contrast agents for nonlinear microscopy. Their properties will be discussed in the light of various biological applications including imaging of stem cells and rare event detection in physiological media.

International audience; Potassium niobate nonlinear nanoparticles are used for the fi rst time to monitor the evolution of embryonic stem cells (ESC) by second harmonic microscopy. These particles feature the complete absence of photo-bleaching and unlimited excitation wavelength fl exibility. The potential of this approach is made evident for tissueregeneration studies and applications, by capturing a high-speed movie of ESCderived cardiomyocytes autonomously beating within a cluster. Time-resolved data are analyzed to retrieve 3D information of the contraction pattern at the cellular level.

International audience; Nonlinear optical nanocrystals have been recently introduced as a promising alternative to fluorescent probes for multiphoton microscopy. We present for the first time a complete survey of the properties of five nanomaterials (KNbO3, LiNbO3, BaTiO3, KTP, and ZnO), describing their preparation and stabilization and providing quantitative estimations of their nonlinear optical response. In the light of their prospective use as biological and clinical markers, we assess their biocompatibility on human healthy and cancerous cell lines. Finally, we demonstrate the great potential for cell imaging of these inherently nonlinear probes in terms of optical contrast, wavelength flexibility, and signal photostability.

A detailed experimental investigation of the formation mechanisms of acentric iron iodate [Fe(IO3)3] nanocrystals in AOT-based reverse micelles according to the water-in-oil (w/o) microemulsion (ME) composition and temperature was performed. A low chemical reaction rate was first demonstrated by means of UV−vis absorption spectroscopy. Attainment of iron iodate crystalline nanorods was then attributed to an oriented aggregation mechanism of 10−20-nm amorphous primary nanoparticles. As for the intermicellar exchange of reactants, the aggregation mechanism was also found to be determined by the ME composition because clear effects of the surfactant and reactant concentrations, the nature of the oil phase, and the water droplet size were observed. Moreover, a combination of dynamic light scattering, X-ray diffraction, and transmission electron microscopy experiments revealed that hyper-Rayleigh scattering is a fast, valuable, and nondestructive alternative to probe, in real time, the crystallization and form...

International audience; We present a technique to characterize ultrashort pulses at the focal plane of a high numerical aperture objective with unprecedented spatial resolution, by performing a FROG measurement with a single nanocrystal as nonlinear medium. This approach can be extended to develop novel phase-sensitive techniques in laser scanning microscopy, probing the microscopic environment by monitoring phase and amplitude distortions of femtosecond laser pulses.

We have developed LiIO3/laponite nanocomposite thin films to form waveguides with quadratic nonlinear optical properties. The films are dip-coated and annealed to induce LiIO3 crystallisation within the laponite matrix. LiIO3 nanocrystal orientation can be controlled using an electric field during the annealing process. In this article we perform the characterisations of the nanocomposite films through m-line spectroscopy and second harmonic generation microscopy (SHGM). Both refractive indexes deduced from m-line spectra and the SHG signal are shown to depend on the nanocrystal orientation distribution, and a relationship between the optical properties and microscopic structure of the films is developed.

A novel Laponite-lithium iodate nanocomposite has been synthesized for nonlinear optical applications. The elaboration starts with the addition of a lithium iodate aqueous solution to a colloidal suspension of Laponite JS. Thin layers, elaborated using the dip-coating technique, form waveguides and the linear dependence between the lithium iodate concentration and the refractive index and the control over the thickness allow one to optimize waveguiding properties. Waveguides show an attenuation of about 2 dB/cm and easily detectable second harmonic generation. For the nonlinear effective coefficient a value of 1.6 pm/V has been measured. X-ray structural characterization shows that after drying and heat-treatment between 150 and 200°C, lithium iodate crystallizes in the matrix with the crystallite size ranging from 20 to 50 nm. Due to the natural dipole moment of lithium iodate, the orientation of nanocrystals could be controlled using external electric field. The influence of the orientation on the nonlinear optical properties has been determined and compared with the simulations based on a matrix model considering the nanocomposite as a stack of linear and nonlinear 1D layers with fixed or random orientation. A good agreement is achieved between the experiment and the simulation.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In recent years, a large amount of activity has been carried out searching new materials for second order non-linear optics. Nanostructured materials composed of a host matrix and optical active nanocrystals form a new part of this research field. Our present work consists in "doping" SiO 2 matrices with 5 to 30% mass of LiIO 3 nanocrystals. Indeed, α-LiIO 3 is a compound known to be very efficient for second harmonic generation (SHG). This nanocomposite glass has been developped using sol-gel technics. Bulk samples have been first studied showing nanocrystallites with size ranging from 50 nm to 400 nm and second harmonic generation (SHG). Then thin layers have been elaborated using dip coating and spin coating technics. Being given that LiIO 3 crystals present structurally a strong dipolar moment, non-linear optical properties could be enhanced using Corona discharges to orientate nanocrystals. This paper relates the fabrication process and the structural and optical characterizations of bulk and thin layer material.

Due to its non-linear optical properties, lithium iodate is commonly used in optical devices. By proton exchange, performed by immersing z -cuts LiIO 3 single crystals in a molten hydrated nitrate salt, we formed a solid solution Li 1− x H x IO 3 layer close to the surface. This modification of the structure increases the refractive index so that a waveguide is created. The index profile obtained by m-lines spectroscopy combined with structure characterization by μ-Raman and X-ray diffraction experiments allows us to describe the diffusion process of hydrogen in LiIO 3 .

We report here micro-transmission measurements of a highly selective and a widely tunable optical filter at 1.55 micrometers . This filter is formed by a (lambda) /2 air cavity sandwiched between two 3.5 alternances InP-air Bragg mirrors. Reflectors and air cavity are fabricated by selective micro- machining of InGaAs sacrificial layers. Measurements have shown a very large wavelength tuning of 108nm for only 4.7V and a filter linewidth of 0.6 nm. Such performances have been possible because of the high reflectivity, large bandwidth and good optical confinement of the InP-air Bragg mirrors.

The design and the fabrication of vertical InP-based micro- opto-electro-mechanical devices are reported. These are based on micromachined III-V semiconductor structures realized by selective removal of adapted sacrificial layers in order to produce Fabry-Perot resonant microcavity. Continuous wavelength running of 50nm around 1.55 micrometers for a 15 volt bias actuation has been demonstrated. Resonant peak full width at half maximum of about 10 nm at 1.5 micrometers has been performed on a InP/air gap multilayered interferometric filter. The integration of absorbing layers inside the cavity will allow us to realize resonant cavity enhanced photonic devices with thinner, and therefore faster, photodetector structures with high quantum efficiencies.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have studied actuable suspended beams that form vertical optical resonant cavities. They are fabricated by sacrificial layers etching techniques on InP. They can be used as tunable optical filters for telecommunication applications. In this paper, we report optical characterizations of those devices. We have used micro reflectivity and optical profilometer measurements to make those characterizations. We have developed a micro- reflectivity experimental setup which uses the confocal principle. We have shown the deformation of the suspended beams and the variation of the reflectivity response induced by electrostatic actuation of the devices.

A Laponite clay-based lithium iodate nanocomposite have been synthesized for nonlinear optical applications. After addition of lithium iodate aqueous solution to a colloidal suspension of Laponite JS, thin layers are elaborated from this sol using dip-coating technique. After drying and heat treatments between 150 and 220°C, LiIO3 crystallizes in the matrix with nanometer size. As a result of their strong dipolar moment, the LiIO3 crystals can be orientated under an external electric field during nucleation. Planar waveguides have been elaborated on glass substrates and studied using m-lines spectroscopy. The experimental nonlinear optical response has been compared to predictions of a model and an effective nonlinear coefficient deff=1.4pm∕V has been measured.

International audience

International audience; Background: Harmonic Nanoparticles are a new family of exogenous markers for multiphoton imaging exerting optical contrast by second harmonic (SH) generation. In this tutorial, we present the application of Hyper-Rayleigh Scattering (HRS) for a quantitative assessment of the nonlinear optical properties of these particles and discuss the underlying theory and some crucial experimental aspects. Methods: The second harmonic properties of BaTiO3, KNbO3, KiTiOPO4 (KTP), LiNbO3 and ZnO nanocrystals (NCs) are investigated by HRS measurements after careful preparation and characterization of colloidal suspensions. Results: A detailed analysis of the experimental results is presented with emphasis on the theoretical background and on the influence of some experimental parameters including the accurate determination of the nanocrystal size and concentration. The SH generation efficiency and averaged nonlinear optical coefficients are then derived and compared for six different types of NCs. Conclusions: After preparation of colloidal NC suspensions and careful examination of their size, concentration and possible aggregation state, HRS appears as a valuable tool to quantitatively assess the SH efficiency ofnoncentrosymmetric NCs. All the investigated nanomaterials show high SH conversion efficiencies, demonstrating a good potential for bio-labelling applications.

This work focuses on the experimental characterization of the linear and nonlin-ear optical properties of harmonic nanoparticles - a new class of biological markers - and of composites based on KDP single crystals with incorporated metal oxide nanoparticles. We have developed several experimental setups, such as light scattering indicatrices technique, laser beam self-action analysis, the third harmonic generation efficiency (THG) measurements, and multiphoton microscopy with femtosecond laser excitation in the 710 - 1300 nm spectral range.The third order susceptibility measurements were performed by analyzing the THG at the interface of a cuvette filled with ZnO colloidal suspensions, showing a susceptibility value close to the reference value of the bulk crystal. In addition, the optical properties of these nanoparticles were studied with multiphoton mi-croscopy. The emission spectra of the nanoparticles show the second harmonic generation (SHG), the THG and photoluminescence signals. The spectral re-sponse has been correlated with the structure of defects in bulk ZnO crystals. In addition, we studied the influence of the incorporation of metal oxide nanopar-ticles into KDP crystals. It has been shown that these nanoparticles can increase the SHG efficiency compared to nominally pure KDP crystal. A set of optical measurements was carried out on these composite crystals, demonstrating the relationship between the third order nonlinear optical effects and the observed SHG efficiency enhancement., Ce travail porte sur la détermination expérimentale des propriétés optiques li-néaires et non linéaires de nanoparticules harmoniques - une nouvelle classe de marqueurs biologiques - et de cristaux massifs de KDP avec incorporation de nanoparticules d'oxydes métalliques. Nous avons mis au point une série de bancs expérimentaux dédiés, comme la mesure des indicatrices de diffusion, la technique I-scan pour la mesure de l’indice de réfraction non linéaire, la mesure de l’efficacité de génération de troisième harmonique (THG), ou le développe-ment d’un microscope multiphotonique sous excitation laser femtoseconde dans le domaine spectral 710 - 1300 nm.Des mesures de susceptibilité non linéaire d’ordre 3 ont été effectuées sur des suspensions colloïdales de nanoparticules de ZnO par la technique de la THG aux interfaces, montrant une valeur de susceptibilité proche de la valeur de réfé-rence des cristaux massifs. Par ailleurs, les propriétés optiques de ces nanoparti-cules ont été étudiées par microscopie multiphotonique. Les spectres d’émission des nanoparticules montrent des signaux de génération de second harmonique (SHG), de THG et de photoluminescence, dont la réponse spectrale a été corrélée avec une étude portant sur la spectroscopie de défauts de cristaux massifs de ZnO. Par ailleurs, nous avons étudié l’influence sur les propriétés optiques de l’incorporation de nanoparticules d’oxyde métalliques dans des cristaux KDP. Il a été démontré que ces nanoparticules peuvent être à l’origine d’une augmenta-tion de l'efficacité de SHG par comparaison avec un cristal de KDP pur. Un en-semble de mesures optiques a été réalisé sur ces cristaux composites, démontrant en particulier la corrélation entre les effets non linéaires d’ordre 3 et l’augmentation observée.

Harmonic nanocrystals with a non-centrosymmetric crystalline structure have nonlinearoptical properties that are particularly interesting for use as optical markers inbiomedical imaging.The Hyper-Rayleigh scattering technique currently used to quantify the secondharmonic response of nanoparticles in suspension has been extended in this work todetermine the third order non-linear susceptibility of different nanomaterials (BiFeO3,ZnO, KNbO3 and LiNbO3). Furthermore, the development of an experimental set-upbased on a wavelength-tunable source has allowed probing the non-linear opticalresonances of the 2nd order (for excitation between 700 nm and 1300 nm) of thesedifferent materials. The spectral response of WS2 nanosheets has also been studiedusing the same system. Finally, we have demonstrated the detection of fourthharmonic signals from a single BiFeO3 nanoparticle using a multiphotonicmicroscopy device combined with a Telecom laser source for future integration ofthese nanoparticles as frequency conversion elements for nanophotonics.; Les nanocristaux harmoniques de structure cristalline non centrosymétrique possèdentdes propriétés optiques non linéaires intéressantes notamment pour une utilisationcomme marqueurs optiques en imagerie biomédicale.La technique de diffusion Hyper-Rayleigh habituellement utilisée pour quantifier laréponse de deuxième harmonique de nanoparticules en suspension a été étendue dansce travail pour déterminer la susceptibilité non linéaire d’ordre 3 de différentsnanomatériaux (BiFeO3, ZnO, KNbO3 et LiNbO3). D’autre part, le développementd’un montage expérimental basé sur une source accordable en longueur d’onde apermis de sonder les résonances optiques non linéaires d’ordre 2 (pour une excitationcomprise entre 700 nm et 1300 nm) de ces différents matériaux. La réponse spectralede nanofeuillets de WS2 a également été étudiée à l’aide du même système. Enfin,nous avons démontré la détection de signaux de quatrième harmonique d’unenanoparticule unique de BiFeO3 à l’aide d’un dispositif de microscopiemultiphotonique associé à une source laser Telecom pour une future intégration deces nanoparticules comme éléments de conversion de fréquence pour lananophotonique.