Parts Of Third-order Susceptibility Research Articles

Nonlinear optical properties of core shell type II quantum dot structures

In this study, CdSe/CdTe Type-II quantum dots (QDs) were synthesized using dropwise method. The core/shell nanocrystals have been characterized by UV–Vis absorption and photoluminescence (PL) spectroscopies, transmission electron microscopy and z-scan technique. Nonlinear properties of each type of quantum dots were studied using femtosecond(fs) z-scan method at 800 nm wavelength with different laser intensities. Fs laser z-scan experimental set-up are used to determine two photon absorption coefficient (β ̴10−12 cm/W) and nonlinear opticalKerrcoefficient (n2 ̴ 10−20 cm2/W. The imaginary and real parts of third order susceptibility (X(3)) were calculated based on β and n2 under different laser intensities for seven different core/shell QDs. Third order susceptibility for CdSe/CdTe type II QDs was found to be about 10−12 esu.

NLO Properties of 2‐Napthol Monoazo Disperse Dyes by DFT and Z‐Scan Technique – A Detailed Study

AbstractThe non‐linear and linear optical properties of 2‐napthol based four monoazo dyes were examined by computational and Z‐scan methods. Time‐dependent (TD)‐density functional theory (DFT) computations were used to evaluate the linear polarizability (α), first‐order hyperpolarizability (β) and second‐order hyperpolarizability (γ) using global hybrid and range separated hybrid functionals at 6–311+ G (d) basis set. The functional, ωB97 performed better in the determination of linear polarizability (α) and ωB97X−D performed better in the determination of the first‐order hyperpolarizability (β) and second‐order hyperpolarizability (γ) among the global hybrid and range separated hybrid functionals. To support our theoretical findings for α, β, and γ, we have correlated with the Hammett‐coefficient (σ), excited state coefficient (σex) as well as by hyper‐hardness (Γ) relations. Third order NLO parameters – non‐linear refractive index (η2), non‐linear absorption coefficient (β), real parts and the imaginary parts of third order susceptibility (χ(3)), and second order hyperpolarizability (γ) were investigated by close and open aperture methods using Z‐scan technique. The –NO2 substituted dye 2 shows higher value of molecular susceptibility (χ(3)), polarizability (α), and hyperpolarizability (β, γ) parameters among the studied azo dyes. They are likely to have potential applications in optoelectronics and photonics.

Optical limiting and optical properties of water soluble CdTe quantum dots prepared through a colloidal chemical route

Luminescent, water soluble, CdTe colloidal QDs were synthesized by simple wet chemical method. The prepared CdTe QD samples were showing wide range of color tunability from green to red when irradiated with UV light. The quantum confinement effect of the synthesized QDs was confirmed using UV–vis absorption and fluorescence spectroscopy. The spherical morphology of the synthesized QDs was confirmed using transmission electron microscopy (TEM). The X-ray diffraction (XRD) analysis indicates that the QDs were having cubic structure. Analysis of the third order nonlinear property using Z-scan technique indicates that the QDs were having two photon absorption properties. Unlike the previous reported results, the variations in the third order nonlinear susceptibility (χ3) was found to be in correlation with emission intensity. The value of imaginary part of nonlinear χ3 and refractive index was found to be of the order of 10−11 and 10-7esu respectively. Imaginary part of χ3 is found to be Gaussian dependent function of reaction time, which provides a possible way of tuning of imaginary part of third order susceptibility. The figure of merit (n2/β) of the synthesized QDs was found to be greater than that for the bulk material. Thus these QDs possess good nonlinear optical characteristics which enable them as a potential candidate for the optical limiting application.

Investigation of nonlinear absorption and the electromagnetically induced transparency in a SMNP-SQD hybrid system by using the Mie theory

By using the Mie theory, nonlinear absorption coefficient and electromagnetically induced transparency (EIT) of a hybrid system consisting of GaAs spherical quantum dot (SQD) with ladder model and parabolic potential in the vicinity of a spherical metal nanoparticle (SMNP) are investigated. The density matrix equations in steady-state are solved and the third order susceptibility is obtained. Then, by using imaginary part of third order susceptibility, the nonlinear absorption coefficient are computed. Then, the effects of radii of SQD and SMNP, distance between SQD and SMNP and control laser frequency on nonlinear absorption coefficient and electromagnetically induced transparency (EIT) are investigated.

Kerr nonlinearity and nonlinear absorption coefficient in a four-level M-model cylindrical quantum dot under the phenomenon of electromagnetically induced transparency

The Kerr nonlinearity and the nonlinear absorption coefficient in a four-level M-model of a GaAs cylindrical quantum dot (QD) with parabolic potential under electromagnetically induced transparency are investigated. By solving the density matrix equations in the steady-state, the third order susceptibility is obtained. Then, by using the real and imaginary parts of third order susceptibility, the Kerr nonlinearity and the nonlinear absorption coefficient, respectively, for this system are computed. The effects of the radius and height of the cylindrical QD are then investigated. In addition, the effects of the control laser fields on the Kerr nonlinearity and the nonlinear absorption coefficient are investigated.

Effect of thickness on the optical nonlinearity of gold colloidal nanoparticles prepared by laser ablation

The effect of thickness on the nonlinear optical properties of Au nanoparticles which produced by laser ablation of high purity gold bulk in distilled water were investigated by employing different optical techniques. Experiments were performed on the 0.3, 0.6, and 1 mm thickness cells of Au nanoparticles-fluid. The effect of nonlinear refractive index of samples on the laser beam broadening was observed. The optical limiting behavior of samples is investigated by measuring the transmitted intensity of the laser beam through the samples. The third order nonlinearity of Au nanoparticles-fluid was measured by using Z-scan data. Results show a positive second order refractive index and absorption coefficient for Au nanoparticles-fluid that are increased in due of increasing the thickness of the cells. The magnitudes of both real and imaginary parts of third order susceptibility of samples are increased by increasing the thickness.

Structural, optical and non-linear optics properties of highly doped molybdenum indium oxide thin film

Molybdenum (Mo)-doped In2O3 thin film with 10 wt% was successfully prepared by evaporation method. After annealing at 600 °C the film changes it colour from very dark to a clear transparent film. SEM and AFM analysis reveal that the film is continuous with high metallic coverage >98 % and exhibits a granular structure with typical grain size of 50 nm. More interestingly, the film shows more than 90 % transparency from visible to near infrared region and with wide optical band gap of 4.26 eV. The widening of the band gap is due to the Burstein–Moss (BM) effect as Mo will occupy In sites within the structure of the film thus increasing the carrier concentration thus enhancing its electrical properties. The nonlinear optical properties of Mo-doped In2O3 film with glass substrate were investigated using z-scan technique. Under cw excitation the film exhibits large reverse saturation absorption and negative nonlinearities. The real and imaginary parts of third order susceptibility of the film were measured and found that the imaginary part which arises from the change in absorption is dominant.

Synthesis of Silver Nanoparticles in DNA Template and Its Influence on Nonlinear Optical Properties

We have synthesized highly stable silver nanoparticles in aqueous solution at room temperature by standard reduction method using de-oxyribo nucleic acid (DNA) as a stabilizing agent. The nonlinear optical properties of above nanoparticles were investigated using Z-scan technique at 532nm.The obtained nonlinear absorption and refraction coefficient is found to be large. The imaginary part of third order susceptibility depends on the concentration of DNA at low pump power of 50MW/ cm2.It is observed that at high pump power of175MW/ cm2, the imaginary part of third order susceptibility does not depend on the concentration of the DNA. The imaginary parts of third order nonlinear optical susceptibility measured by Z-scan technique revealed that silver nanoparticles in DNA template are potential candidate for optoelctronic device applications.The silver nanoparticles in DNA template show good optical limiting property.

OPTICAL AND STRUCTURAL PROPERTIES OF SILVER NANOPARTICLES EMBEDDED IN INDIUM OXIDE FILMS

Nanoparticles of silver-embedded indium oxide thin films have been prepared on glass and silicon substrates. Silver concentration were 3 wt.% and 5 wt.% as measured by X-ray fluorescence. X-ray diffraction reveals that indium oxide of these samples remains amorphous even after pre-annealing at 400°C. The optical absorption of the samples manifests the surface plasmon resonance (SPR) phenomena, which varies with Ag content. The Ag nanoparticles radius was estimated with Mie classical theory by using the SPR data analysis. The nonlinear optical properties of films on glass substrate were investigated using z-scan technique. Under cw excitation the films exhibit large reverse saturation absorption and negative nonlinearities. The real and imaginary parts of third order susceptibility of the samples were measured and the imaginary part which arise from the change in absorption is found to be dominant.

LINEAR AND NONLINEAR OPTICAL PROPERTIES OF SILVER NANOPARTICLES STABILIZED BY BOVINE SERUM ALBUMIN

We have synthesized highly stable silver nanoparticles in aqueous solution at room temperature by standard reduction method using bovine serum albumin (BSA) as a stabilizing agent. The nonlinear optical properties of nanoparticles were investigated using Z-scan technique at 532 nm. The obtained nonlinear absorption coefficient and negative nonlinear refractive index is found to be 88.36 cm/GW and -5.1 × 10-7esu respectively. The real and imaginary part of third order susceptibility of silver nanoparticles is found to be 1.553 × 10-7esu and 0.7 × 10-7esu respectively. The silver nanoparticles in BSA template show good optical limiting property.

Spectral dependence of third order nonlinear optical susceptibility of zinc phthalocyanine

Wavelength dependence of saturable absorption (SA) and reverse saturable absorption (RSA) of zinc phthalocyanine was studied using 10Hz, 8ns pulses from a tunable laser, in the wavelength range of 520–686nm, which includes the rising edge of the Q band in the electronic absorption spectrum. The nonlinear response is wavelength dependent and switching from RSA to SA has been observed as the excitation wavelength changes from the low absorption window region to higher absorption regime near the Q band. The SA again changes back to RSA when we further move over to the infrared region. Values of the imaginary part of third order susceptibility are calculated for various wavelengths in this range. This study is important in identifying the spectral range over which the nonlinear material acts as RSA based optical limiter.

Optical Properties of Au Nanoparticle Dispersed (Ba,Sr)TiO3 Thin Films

Au nanoparticles dispersed (Ba,Sr)TiO3 thin films were fabricated using alternating sputtering method. With the nominal thickness of Au layer of 1 nm, the spherical Au particles of 3.83 nm size were obtained showing the spatial distribution referred to a Maxell-Garnett type effective medium geometry. The film shows the characteristic surface plasmon resonance absorption band at 571 nm. Based on the effective medium theory, the linear optical functions of the films were characterized. The third-order optical nonlinearity was analyzed by a single beam Z-scan technique with a picosecond pulse laser. The real and imaginary parts of third-order susceptibility can be resolved at several wavelengths around the SPR by virtue of wavelength tunable optical parametric generator. The maximum absolute value of third-order susceptibility as large as 3.847 × 10− 8 esu were obtained at the SPR frequency.

Nonlinear Optics and Optical Limiting Properties of Multifunctional Fullerenol/Polymer Composite

The nonlinear optics and optical limiting properties of materials based on multifunctional fullerenol and poly (styrene-co-4-vinylpyridine) matrix were studied using 7 ns pulses of nanosecond laser operating at 532 nm wavelength. The observed imaginary and real parts of third order susceptibility of the fullerenol/polymer composite are found to be lower than that of its parent C60. The optical limiting performances of fullerenol and fullerenol incorporated with poly(styrene-co-4-vinylpyridine) have been proved to be poorer than that of C60 due to their higher limiting thresholds. Concentration dependence of poly(styrene-co-4-vinylpyridine) containing 32 mol% has been mainly contributed to the optical limiting performance of fullerenol.

Measurements of complex third-order optical susceptibility in a collinear pump–probe experiment

We demonstrate simultaneous measurement of the real and the imaginary parts of third-order susceptibilities by use of a collinear pump-probe technique. This technique allows for good results and simple implementation. The signal analysis is based on the particular oscillatory signature versus the pump-probe delay allowed by the collinear configuration. Results are compared with interferometric measurements of a SF59 (Schott) glass sample.