Imaginary Parts Of Third-order Susceptibility Research Articles

Third-order optical nonlinearity and multiferroicity of nanoparticles thin films of isovalent rare earth Y3+ ion substituted BiFeO3

Present work reveals the multiferroic and nonlinear optical properties of pristine and Yttrium (Y3+) substituted BiFeO3 nanoparticles synthesized by sol-gel technique, and fabricated thin films of the nanoparticles. The nanoparticles thin films were deposited on glass substrates with an average thickness of 85 nm by the thermal evaporation method in a high vacuum of 10−6 Torr. The structural and morphological studies were done by using XRD, Fullprof, XPS, AFM, FESEM and TEM with SAED. Further BET method was used to find out the surface area, pore size and pore volume of the nanoparticles. The multiferroic properties of Bi1-xYxFeO3 (x = 0.0, 0.5, 0.10, 0.15) have been investigated using VSM (magnetic) and P-E loop tracer (electrical). The doping of magnetic Y3+ions in host BiFeO3 nanoparticles modified and improved the optical, structural, multiferroic properties enormously. Linear optical properties were characterized by UV–Visible, Raman, and Photoluminescence. Third-order nonlinear absorption coefficient (β) and the imaginary part of third-order susceptibility (χi3) of Bi1-xYxFeO3 (x = 0.0, 0.5, 0.10, 0.15) have been investigated using a single beam Z-scan technique with a continuous wave (CW) diode laser of 520 nm wavelength. The films exhibit saturation absorption (SA) behavior and it increases on increasing the Yttrium (Y3+) substitution in BiFeO3. Thus, the NLO behavior of the films makes it an auspicious material for application in optoelectronic devices.

Self-Defocusing of Light in Ethanol Around 1550 nm

We experimentally investigated the third-order nonlinear optical response of absolute ethanol around 1550 nm. The real and imaginary parts of third-order susceptibilities are distinguished by Z-scan method, which demonstrated that absolute ethanol exhibited saturable absorption and self-defocusing behaviors with nonlinear refractive index n 2∼−10−14 m2/W. In addition, the experimental results via self-phase modulation method also verified the comparable nonlinear optical response of absolute ethanol. This work is expected to provide insights for the nonlinearities of organic solvents, and may broaden the potential of cost-effective nonlinear optoelectronic devices.

Third-order optical nonlinearities of 1,5-Diaminoanthraquinone for optical limiting application

Third-order nonlinear optical properties of 1,5-Diaminoanthraquinone have been studied. The vibrational and optical properties of the compound were analysed experimentally by FT-IR, FT-Raman and UV–visible spectroscopic characterization combined with theoretical DFT method. Intermolecular interactions in the compound have been confirmed by Hirshfeld surface and its associated two-dimensional fingerprint plots. First- and second-order hyperpolarizabilities of the title compound were computed theoretically by B3LYP and CAM-B3LYP hybrid functionals at DFT level. The third-order nonlinear optical parameters such as nonlinear refractive index (n2), nonlinear absorption coefficient (β), real, imaginary parts of third-order susceptibility (χ(3)) and second-order hyperpolarizability (γ) of the title compound were measured experimentally by open and closed aperture Z-scan technique. The Z-scan results confirm the reverse saturable absorption behaviour and positive nonlinear refractive property of the dye. These attractive third-order nonlinear properties suggest the title compound can be a good candidate for optoelectronic and photonic applications, furthermore the optical limiting property and laser damage threshold studies recommend the compound can be a promising material for laser-assisted applications.

Experimental and theoretical investigation of third-order nonlinear optical properties of azo dye 1-(2, 5-Dimethoxy-phenylazo)-naphthalen-2-ol by Z-scan technique and quantum chemical computations

The structural and optical characterization of the 1-(2,5-Dimethoxy-phenylazo)-naphthalen-2-ol were analyzed experimentally by FT-IR, FT-Raman and UV-visible spectroscopic technique and theoretical studies by density functional theory method. The charge transfer interactions leading to nonlinear properties taking place in the molecule can be studied by HOMO-LUMO analysis and natural bond orbital analysis. The second-order hyperpolarizability (γ) was calculated at DFT level and it show good agreement with the experimental result. The third-order nonlinear optical parameters such as nonlinear refractive index (n2), nonlinear absorption coefficient (β), real, imaginary parts of third-order susceptibility (χ(3)) and second-order hyperpolarizability (γ) were measured experimentally by closed and open aperture Z-scan technique. Z-scan measurements were performed using Q-switched Nd: YAG laser with 5 ns pulses at 532 nm with different dye concentrations and intensities. The open and closed aperture Z-scan measurements confirms, the dye exhibit saturable absorption property and positive nonlinearity. The result also shows that there is an increasing trend in the values of the nonlinear refractive index and the third order nonlinear susceptibility while increasing concentration. These attractive third-order nonlinear results indicated that 1-(2,5-Dimethoxy-phenylazo)-naphthalen-2-ol have potential applications in optoelectronics and photonics.

Z-scan measurements of the third-order optical nonlinearities and vibrational spectral studies by DFT computations on azo dye 1-(2-Methylphenylazo)-2-napthol

The nonlinear optical properties of azo dye 1-(2-Methylphenylazo)-2-napthol have been studied. The complete vibrational features and electronic absorption spectra of the title compound were analyzed by FT-IR, FT-Raman and UV–visible spectra combined with density functional theory and time-dependent density functional computations respectively. Nonlinear optical behavior was investigated by calculating the second-order hyperpolarizablity at DFT level. Third-order nonlinear optical parameters of 1-(2-Methylphenylazo)-2-napthol were measured using closed and open aperture Z-scan technique. The Z-scan result confirms, the dye exhibit self-focusing effect and the sign of the refractive nonlinearity is positive. The nonlinear refractive index (n2), nonlinear absorption coefficient (β), real and imaginary parts of third-order susceptibility (χ (3)) and second-order hyperpolarizability (γ) are calculated. The calculated results indicated that 1-(2-Methylphenylazo)-2-napthol have potential applications in optoelectronics and photonics.

Controlling the sing and magnitude of Kerr nonlinearity in four-level N-type EIT medium

Third-order nonlinear susceptibility in a four-level system with N-type configuration is studied by applying the electromagnetically induced transparency (EIT). The system is irradiated with a weak probe and two strong coupling fields. Behaviour of real (Kerr nonlinearity) and imaginary parts of third-order susceptibility and linear absorption spectrum of probe field is investigated with coupling field intensity and its frequency detuning. Results are shown that, the sign of both imaginary and real parts of third-order nonlinear susceptibility in one of Kerr peaks, changes from positive to negative with increasing the coupling field intensity. The EIT windows are not sensitive for intensity but extend for negative and shortened for positive detuning's. Furthermore, the magnitude of Kerr and nonlinear absorption (or gain) peaks efficiently modify with increasing the intensity. This can be important in practical applications such as lasing without inversion, subluminal and superluminal propagation and optical limiting effect based on self-focusing or self-defocusing process.

Influence of Orbital Hybridization on Kerr Nonlinearity of a Heavy Metal Borate Glass: Scaling of Polarizability and the Imaginary Contribution of Optical Susceptibility

Photonics properties of glasses can be designed by controlling their complex Kerr nonlinearity. Chemical structure and bonding properties are considered as the origin of glass third-order susceptibilities. Investigation of the role of orbital hybridization on the glass electronic polarizability and third-order susceptibility is carried out. Thus, series of heavy metal lead borate glass of the composition 0.25B2O3–0.75PbO is prepared by melt quenching technique. Orbital hybridization, as a linear combination for valence electron wave functions of p- and d-block elements, is obtained through structural co-substitution of very small contents of Cr2O3 and/or SeO2, by B2O3. It get succeed to tune the glass nonlinear optical characteristics such as; the complex components of third-order susceptibility. Scaling roles describing the relations between oxide ion polarizability and index of refraction and between imaginary part of third-order susceptibility and band gap energy are proposed. The glasses exhibit zero-dispersion wavelength at 1.55 μm band which is needed for telecommunication devices. The polarizability approach is applied to analyze and explain the obtained glass properties.

Resonant-type third-order optical nonlinearity and optical bandgap in multicomponent oxide glasses

Optical nonlinearity or the nonlinear hyperpolarizability of amorphous materials (e.g., glasses) is related directly to the complex third-order susceptibility. The imaginary part of third-order susceptibility affects negatively the maximum data rate in telecommunication systems. In addition, many transition metals containing glasses have bandgaps with semiconductor-like behavior. So, due to the necessity of operation near the absorption band edge, the study of optical nonlinearity and band structure in glasses is very essential. In this work, we investigated the relationship between the imaginary third-order nonlinear susceptibility and the bandgap of some different series of prepared oxide glasses. A universal empirical formula is given to correlate the imaginary part of the third-order nonlinear susceptibility of the glasses and their optical bandgaps. The obtained nonlinearity is discussed in view of available theories and mechanisms.

Evolutions of polarization and nonlinearities in an isotropic nonlinear medium

The evolutions of polarization and nonlinearities in an isotropic medium induced by anisotropy of third-order nonlinear susceptibility were studied experimentally and theoretically. The anisotropy of imaginary part of third-order susceptibility was verified to exist by the change of ellipticity of polarization ellipse in the isotropic nonlinear medium CS(2). The changes of nonlinear refraction and nonlinear absorption depending upon the ellipticity of polarization ellipse are also presented. The numerical simulations based on two coupled nonlinear Schrödinger equations (NLSE) provide an excellent quantitative agreement with experimental results.

Nonlinear optical characteristics of self-assembled films of ZnO

In the present work, we have investigated the nonlinear optical properties of self-assembled films formed from ZnO colloidal spheres by z-scan technique. The sign of the nonlinear component of refractive index of the material remains the same; however, a switching from reverse saturable absorption to saturable absorption has been observed as the material changes from colloid to self-assembled film. These different nonlinear characteristics can be mainly attributed to ZnO defect states and electronic effects when the colloidal solution is transformed into self-assembled monolayers. We investigated the intensity, wavelength and size dependence of saturable and reverse saturable absorption of ZnO self-assembled films and colloids. Values of the imaginary part of third-order susceptibility are calculated for particles of size in the range 20–300 nm at different intensity levels ranging from 40 to 325 MW/cm2 within the wavelength range of 450–650 nm.

Non-resonant third-order non-linear optical properties of amorphous GeSe 2 film

The real and imaginary parts of third-order susceptibility of amorphous GeSe 2 film were measured by the method of the femtosecond optical heterodyne detection of optical Kerr effect at 805 nm with the 80 fs ultra fast pulses. The results indicated that the values of real and imaginary parts were 8.8 × 10 −12 esu and −3.0 × 10 −12 esu, respectively. An amorphous GeSe 2 film also showed a very fast response within 200 fs. The ultra fast response and large third-order non-linearity are attributed to the ultra fast distortion of the electron orbits surrounding the average positions of the nucleus of Ge and Se atoms.

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.

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.