Nonlinear Optical Susceptibility Research Articles

Analyzing coherent and incoherent optical susceptibilities in four-wave mixing: stochasticity, symmetry, and intramolecular coupling

The nonlinear optical susceptibilities are analyzed in their optical propagation length considering the incoherent-coherent contributions with the dependence on the relaxation times. In addition, some symmetry properties of the Four-Wave mixing (FWM) signal concerning the frequency detuning exchange are used in the study, without restricting ourselves to the maxima of population oscillations. We analyze the behaviors of these optical responses in a vibronic coupling scheme using a molecule model consisting of two coupled harmonic curves of electronic energies with displaced minima in position and nuclear energies. The solvent effect in our model is treated through the natural Bohr frequency shift to a time-dependent function, with explicit manifestations in its comparison as if the upper state were broadened. Our results for both FWM signal propagation and nonlinear optical susceptibilities are sensitive to the intramolecular coupling parameters, solvent stochasticity, and perturbation order for the treatment of the weak probe beam. The consideration of a second-order probe beam in FWM would not represent a significant contribution to the predicted results, since its percentage contribution is negligible within the model development framework; however, this contribution becomes important when increasing the ratio between longitudinal and transverse relaxation times.

New polymeric nanocomposite thin films for transparent optoelectronics: Impact of In(acac)3 on the structural, optical and photoelectrical characteristics of PVA films

Concerning the rapid progress in elastic and transparent optoelectronics, the need for cost-effective materials for transparent optoelectronic devices has become a mainstream research trend. Therefore, this report aimed to explore the modifications of the PVA characteristics due to In(acac)3 doping. New PVA:In(acac)3 nanocomposite thin films were fabricated using a cost-effective and facile spin-coating technique with varying the In(acac)3 loading concentration. The structural and molecular feature variations of PVA have been tracked using XRD and FTIR techniques, respectively. Furthermore, by varying In(acac)3′s concentration, the fabricated films' linear/nonlinear optical properties have been investigated symmetrically using the UV–visible-NIR spectrophotometric technique. The measured transmittance spectra of the prepared films showed the tunability of the energetic position of the fundamental edge while conserving the high transparency. The energy gap and Urbach energy of the prepared thin films have been calculated as a function of doping concentration. The nonlinear refractive index and optical susceptibilities were estimated for all the fabricated films. On the other hand, the photodetection response of the fabricated Schottky barrier devices was tested. The fabricated devices showed pronounced UV response, where the photocurrent density was significantly enhanced under UV illumination up to 0.1 mA/cm2 for the 20 wt.% In(acac)3 doped films. The photodetection performance of the manufactured nanocomposite thin films under repeatable On/Off switching cycles was tested. The optimum doping concertation of In(acac)3 was determined in terms of the analyzed optical and photodetection characteristics to be 20 wt.%. The obtained results support the careful reconsideration of the possibility of exploiting some cheap polymers as important components in advanced optoelectronic applications.

Structural, linear/non-linear optical, and optoelectrical properties of PVB/Bi2WO6 nanocomposite for industrial applications

Nanocomposite films composed of polyvinyl butyral (PVB) and Bi2WO6 were produced through solution casting. The goal of this investigation was to examine the effects of different Bi2WO6 concentrations (0%, 2%, and 4% wt.) on the linear/non-linear optical and optoelectrical properties, as well as the structure and dispersion of films of PVB/Bi2WO6 nanocomposite. The direct band gap Eg1 value falls from 5.1 eV to 3.83 eV with the progressive increase in Bi2WO6 content from 0% to 4% wt., while indirect band gap Eg2 decreased from 4.1 eV to 2.89 eV. Conversely, the PVB + 4% Bi2WO6 nanocomposite increased Urbach’s energy (EU) from 1.00 eV for pure PVB to 1.97 eV. Moreover, our research has documented the impact of different concentrations of Bi2WO6 on a range of optical properties, including the refractive index ( n), extinction coefficient ( k), and other pertinent parameters. Utilizing the real and imaginary components of the dielectric constants εr and εi, an investigation was carried out into the dielectrics’ behavior and the optoelectrical parameters’ calculation. Furthermore, investigations were performed on the linear optical susceptibility, the non-linear refractive index, and the third-order non-linear optical susceptibility concerning the concentrations of Bi2WO6. In addition, the results indicated that varying Bi2WO6 concentrations substantially affect the oscillator strength, average oscillator wavelength, and optical conductivity. The nanocomposite films of PVB/Bi2WO6 concentrations exhibited favorable associations between their optoelectrical and non-linear/linear optical parameters, rendering them viable candidates for implementation in flexible electronic devices and radiation shielding.

Novel schiff base-azide metal complexes: Synthesis, spectral, nonlinear optics, and DFT studies

In order to enhance nonlinear optics (NLO)-based technologies, current research focuses on the design and synthesis of coordination materials. In this context, to investigate spectral and theoretical linear optical (LO)/nonlinear optical (NLO) behaviors, novel metal complexes including azide {[Mn (L1)2(N3)2], (9), [Ni(L1)2(N3)], (10), [Co2(L1)2(N3)2]⋅2H2O, (11); L1: N-(pyridin-2-ylmethylene)methanamine} were synthesized. The vibrational and electronic spectral features of complexes 9–11 were investigated by UV–Vis and FT–IR spectra. Depending on the central metal ion and coordination geometries of complexes, the microscopic static nonlinear behaviors were examined by using the CAM-B3LYP/and ωB97XD/6–311 + G (d,p)//LanL2DZ levels of density functional theory (DFT). Furthermore, the vibrational and electronic properties of complexes 9–11 based on the same levels of time-dependent/density functional theory (TD-DFT/DFT) were surveyed. Additionally, the theoretical χ(1), χ(2), and χ(3) parameters, known as linear optical, second-, and third-order nonlinear optical susceptibility tensors, as well as linear, second-, and third-order polarization parameters (P(1), P(2), and P(3)) for complexes 9–11 were examined. The greatest <β(0; 0,0)> value for complex 10 found to be 262.55 × 10−30 esu using CAM-B3LYP level is 820.5 and 2019.6 times higher than the urea findings (0.32 × 10−30 esu and 0.130 × 10−30 esu). The <γ(0; 0,0,0)> results indicate that complex 9 having the highest value obtained at 2216.40 × 10−36 esu using CAM-B3LYP level is 47.76 and 316.63 times greater than those of pNA (15 × 10−36 esu) and urea (7 × 10−36 esu), respectively. Complexes 10 and 9 demonstrated promising microscopic second-order and third-order NLO features, respectively. Our research is anticipated to provide insight into NLO materials that may have applications in optoelectronics and telecommunication field.

Computational Evaluation of the Structural, Topological, and Solvent Effects on the Nonlinear Optical Properties of 1-Methylurea Butanedioic Acid Crystal

In silico investigation of the effects of a molecule’s framework and surroundings on its nonlinear optical (NLO) response is still an active topic of study in the fields of photonics and optoelectronics. NLO materials play a crucial role in modern photonics and optoelectronic technologies. Presented here is a comprehensive theoretical analysis of the structural, topological, and NLO features of 1-methylurea butanedioic acid (MUBA) alongside solvent effects (water, DMSO, and benzene) using the DFT method at the B3LYP(D4)/6–311++G(d,p) level. Geometric and infrared parameters were calculated and compared with experimental values. The analysis using atoms in molecules (AIM) and the independent gradient model (IGM) reveals the presence of two noncovalent intermolecular interactions: N4–H16⋯O12 and O6–H25⋯O3, which stabilize the crystal structure. The natural bond orbital (NBO) analysis reveals that the LP(1)N4 ⟶ π∗(C2-O3) interaction is the most stabilizing and is enhanced in solvent environments. NLO data show that the first (βtot) and second (γ) hyperpolarizability values of MUBA are approximately 0.6–1.1 and 8.3–17.0 times higher than those of urea. In addition, the quadratic and cubic responses of MUBA are significantly reduced and increased, respectively, in solvent environments. Based on its NLO susceptibilities, MUBA exhibits SHG, EOPE, OKE, and EFISHG properties, suggesting its potential application in the production of optoelectronic devices and optical limiting. This study enhances our understanding of the factors influencing the NLO behaviour of organic crystals, providing valuable insights for designing materials with enhanced NLO characteristics. The implications extend to industries such as telecommunications and computing, where faster data transmission rates are in high demand.

Optical non-linearities and applications of ZnS phosphors

Optical non-linearities play a crucial role in enabling efficient and ultrafast switching applications that are essential for next-generation photonic devices. ZnS phosphor material produces the best results in terms of increased luminescence quantum yield when doped with certain impurities. Nevertheless, the investigation of the third-order non-linear optical susceptibility of the phosphor materials can be exploited for various switching applications. In this regard, we review the recent advancements in the investigation of non-linear optical properties of ZnS phosphors, where the knowledge of absorption and refraction is utilized in various optical and detector applications. Furthermore, the review highlights strategies employed to enhance the non-linear optical response of phosphor materials as well as a general discussion of an attosecond optical switching scheme which can be used to fabricate devices with petahertz speeds. Consequently, we provide a solution to the unsolved problem of the significant extension of optical limiting applications to switching applications by developing design strategies to manipulate conventional ZnS phosphor material. The potential challenges and future prospects of utilizing phosphor materials for switching applications are also addressed. The strategies for manipulating ZnS phosphor can be generalized for a broad range of other materials by minimizing linear and non-linear losses, while enhancing the values of the non-linear refractive index coefficient. We propose that the figure-of-merit of ZnS material can be enhanced by using a suitable combination of pump and probe wavelength values, which can be useful for optical switching applications.

Exploration of the optical characteristics in sol-gel synthesized europium-doped zinc oxide thin films for potential optoelectronic use: a comprehensive characterization approach

Abstract In this study, we present our findings on the spin coated pure Zinc-Oxide (ZnO) nanowire arrays and Europium doped ZnO (Eu3+: ZnO) nanostructure thin films. These arrays were grown on soda lime (silica) coated glass substrate. We conducted a comprehensive analysis of the structural and optical properties of the as-synthesized nanostructures. The characterization techniques included x-ray Diffraction, FESEM Analysis, Raman Spectroscopy, Photoluminescence and UV–vis Analysis. The XRD findings indicate the incorporation of Europium (Eu3+) into the ZnO crystalline lattice, potentially replacing Zn2+ ions. This doping with Europium (Eu3+) led to a reduction in crystalline size, as determined by Scherrer’s equation decreasing from 48 nm to 28 nm demonstrates a decrease in defects within the films. Raman Shift analysis revealed changes in the optical properties of films with inclusion of Europium in host matrix. Photoluminescence studies demonstrated a distinctive 5D0 to 7F2 transition arising from the Eu3+ ions, observed at approximately 612 nm. We have thoroughly examined the optical characteristics of both Europium-doped and pure ZnO thin films through a systematic study. The optical properties were assessed by analyzing the absorption spectra (220–600 nm) and transmission spectra within the wavelength range of 200 to 1200 nm. The film exhibited an impressive 80% transparency, particularly noteworthy for window layer application. The refractive index (n), extinction coefficient (k) and all other associated parameters were found to be impacted by the doping of Europium. The refractive index dispersion relation has been explored using a single oscillator model. Furthermore, the non-linear optical susceptibility (χ 3) and non-linear refractive index were computed using semi-empirical relationships based on the linear optical parameters. The Europium (Eu3+) doping in ZnO led to an increase in the χ 3 value elevating it from 4.07 × 10–1° to 5.91 × 10–1° e.s.u. These findings suggest that Europium-doped ZnO nanostructures have the potential to be a promising platform for the development of efficient multispectral light-emitting diodes (LED’s) and optical devices.

Directional growth of 2-ethylimidazolium d-tartrate crystal along (001) and investigation of optical properties for optical limiting applications

A single crystal of 2-Ethylimidazolium d-Tartrate (2EIMDT) was grown along the preferred direction of (001) by the Sankaranarayanan-Ramasamy method. The growth direction was confirmed by X-ray Diffraction analysis. The optical homogeneity and the defect analysis of the grown crystal were carried out using birefringence interferometry, Williamson-Hall plot, and chemical etching. They revealed that the grown crystal possesses good optical and crystalline quality. Using the optical transmission spectrum, the optical band gap and Urbach energy were estimated to be 5.1 eV and 140 meV, respectively. The temperature dependence of the refractive index and thermo-optic coefficient were measured using the prism coupling technique for different wavelengths. The thermo-optic coefficient was found to be negative with values ∼10−5/°C. The laser damage threshold was estimated to be 6.5 GW/cm2 for a 1064 nm laser. Vickers micro-hardness study revealed that the (001) plane of the crystal is characterized by Meyer's index of 1.93. From the Z-scan measurement, it was found that the grown crystal exhibits two-photon absorption characteristics and the obtained imaginary parts of the third-order nonlinear optical (TONLO) susceptibility is 1.95 × 10−14 esu. Additionally, the onset optical limiting threshold was estimated to be 3.89 × 1012 W/m2 which indicates the potential of 2EIMDT for optical limiting applications.

Characterizing the properties of Li2O–B2O3–SiO2– P2O5–TiO2 glasses: A multidimensional investigation of their structure, optical properties, and gamma-ray shielding capability

A series of lithium borophosphosilicate glass doped with TiO2 was produced with melt-quenching procedure with empirical formula (20-x) Li2O–40B2O3–20SiO2– 20P2O5–xTiO2, where x can be changed between 0 and 16 mol%. By adding titanate, the bulk density of BSPLT glass increased from 3.61 to 4.812 g/cm3. The amorphous nature of glasses is demonstrated by XRD analysis. Different optical characteristics, including the refractive index and optical band gap (Eopt), were determined by recording optical absorption spectra in the 250–2500 nm range. The observed range (Eopt) values from 3.09 eV to 2.64 eV suggests that the (Eopt) decreases as the content of TiO2 in the BSPLT samples increases. The linear optical susceptibility χ(1), third-order non-linear optical susceptibility (χ(3)), and the non-linear refractive index (n2) were determined. Higher-density glasses provide more effective radiation shielding because they are better at absorbing and slowing down radiation particles. BSPLT-16 glass exhibits the highest FNRCS value among the samples tested, indicating its superior performance in shielding against fast neutrons. It is noted that the BSPLT-16 sample, has the highest density among the glasses tested, shows the greatest effective for radiation shielding applications according to the results.

Testing the physical properties stability of Zinc (8-hydroxyquinoline) thin films toward stable photodetection performance: Effect of annealing

In this study, the effect of thermal annealing on the structural and optical properties of thermally evaporated zinc (8-hydroxyquinoline) (ZnQ2) thin films is discussed in detail. Differential scanning calorimetry analysis revealed the thermal stability of the ZnQ2 powder up to 540 K. Fourier transform infrared spectrometer characterizations revealed the stability of the ZnQ2 molecular structure up to 423 K. The annealing effect on the surface morphology of the ZnQ2 films was tracked using the field emission scanning electron microscope (FE-SEM) technique, which revealed grain growth up to 423 K achieving the highest surface smoothness. Moreover, UV–Vis-NIR spectrophotometric measurements were used to examine how annealing affects the optical characteristics of the prepared films. The optical bandgap of ZnQ2 augmented when the annealing temperature increased to 373 K. The dispersion parameters were estimated from the analysis of the complex refractive index following the single oscillator model. The behavior of nonlinear optical susceptibility suggested the validity of utilizing ZnQ2 thin films in IR and UV optical switching applications and UV photodetection applications.

Improvements of multifunctional spintronic and optoelectronic applications of nanostructured Eu-doped ZnS thin films through magnetic and linear, nonlinear optical investigations

This study describes the spintronic and optoelectronic improvements upon Eu substitution in Zn atomic site of the nanostructure ZnS thin films. The electron beam deposition technique has been used to deposit a series of Zn1-xEuxS thin films on a glass substrate with different Eu dopants (x = 0, 0.01, 0.03, 0.05, and 0.08). The nanostructure nature of the Eu-doped ZnS thin film has been confirmed from structural and morphology studies performed by the X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. XRD investigations further show a hexagonal-type structure with no detectable extra phases with the lattice parameter c increasing, while a decrease linearly with increasing Eu-dopant in the ZnS hosted lattice. The microstructures analysis reveals a reduction in the mean crystallite size and increasing in the lattice strain of the films with rising Eu doping. The Fourier transform infrared spectra display the existence of chemical bonds in the thin films whereas photoluminescence reveals near-band edge emission. The linear optical parameters were obtained from the analysis of the transmission data measured by the spectrophotometer technique. The results reveal that the band gap energy (EgOpt) reduces by raising ohe Eu doping ratio, which is ascribed to the structural deformation (strain and/or defects) confirmed from structural analysis, density of localized states and PL measurements. The index of refraction n was calculated using the Swanepoel method. The values were found to increase as the level of Eu doping grows, which is associated with the rise in polarizability. Wemple and DiDomenico's (WDD) model was utilized to compute the dispersive and oscillator energies (Eo, and Ed), the nonlinear absorption coefficient βc, nonlinear refractive index n2, and nonlinear optical susceptibility χ3. The results demonstrate that the adjustability of EgOpt , Eo, and Ed of ZnS: Eu films is conducted to improve the nonlinear optical characteristics, providing it well-suited for optoelectronic device implementations. On the other hand, ZnS doped with Eu film displays inherent ferromagnetic properties at room temperature, as evidenced by the results of the magnetic investigation. This finding could be attributed to the presence of sulphur defects (vacancies), as supported by photoluminescence (PL) measurements, which lead to the creation of the bound magnetic polaron. These discoveries indicate the potential of utilizing Eu-doped ZnS film in the effective development of spintronic devices.

Tailoring the optical performance of sprayed NiO nanostructured films through cobalt doping for optoelectronic device applications

The current study aims to tailor the structural and nonlinear/linear optical characteristics of NiO nanostructures for optoelectronic applications. The spray pyrolysis procedure was applied to synthesize Ni1-xCoxO nanostructured films (x; 0, 0.04, 0.08, 0.12, 0.16 and 0.20). The functional groups and morphological investigation were performed by the FT-IR and SEM techniques. The structural and optical properties were investigated based on XRD and UV–vis measurements. The XRD investigations reveal that all samples have a cubic crystalline structure. The UV–vis analysis shows that the optical absorption of NiO nanostructures increased, and the energy bandgap decreased from 3.85 eV to 3.40 eV through cobalt doping. The Herve-Vandamme model was applied to investigate the linear refractive index for all samples. The nonlinear optical (NLO) behavior of all samples has been investigated. A significant improvement was accomplished through cobalt doping in the linear refractive index, optical conductivity, dielectric constants, NLO susceptibility and NLO refractive index of NiO. The achieved results suggest that cobalt-doped NiO nanostructured films have potential applications in linear/nonlinear optical devices and data storage.

Defects assisted the enhancement of optical and ferromagnetism in Zn1-xCoxS quantum dots: Toward efficient optoelectronic and spintronic applications

Colloidal Co-doped ZnS Quantum dots (QDs) were successfully synthesized through a facile and effective chemical co-precipitation method using polyethylene glycol (PEG) as a capping agent. A comprehensive study on the structure, optoelectronic, and magnetic properties of ZnS: Co2+ QDs was thoroughly carried out using diverse characterization techniques. Transmission electron micrographs reveal spherical QDs with a mean particle size of 5 ± 0.5 nm, whereas the X-ray diffraction (XRD) analysis and Raman spectroscopy confirm the exclusive presence of cubic ZnS phase structure, without any signs of Co-related impurity phases. Energy-dispersive x-ray (EDX) analysis verifies the presence of only three elements: Zinc, Cobalt, and Sulphur, with nearly stoichiometric proportions. X-ray photoemission (XPS) analysis confirmed the presence of Co2+ ions in the divalent oxidation state as well as the fair existence of sulphur vacancies. Optical measurements demonstrate that Co-doping in ZnS leads to a decrease in the optical band gap owing to the presence of defects that create localized states within the band structure. In addition, the refractive index (n) is found to increase with Co-doping level due to the increase in the polarizability. The outcomes of optical properties reveal that the tunability of the optical band gap and dispersive oscillator parameters in Co-doped ZnS QDs results in an enhancement of the non-linear optical parameters, such as third-order non-linear optical susceptibility χ(3), and non-linear refractive index n2, rendering them well-suited for applications in optoelectronic devices. Furthermore, the room-temperature photoluminescence (PL) spectra revealed that the Co-doped ZnS QDs have two broad emission bands, including the blue emission, and the green emission. By varying the level of Co-doping, it becomes possible to effectively control the relative PL intensities of dual-color emissions, highlighting their potential for producing adjustable color outputs. The room temperature ferromagnetic behaviour of the QDs has been observed and analyzed in accordance with the bound magnetic polarons model. These findings suggest that Co-doped ZnS QDs can be utilized effectively in the design of spintronic devices.

Derivation of Miller’s rule for the nonlinear optical susceptibility of a quantum anharmonic oscillator

Miller’s rule is an empirical relation between the nonlinear and linear optical coefficients that applies to a large class of materials but has only been rigorously derived for the classical Lorentz model with a weak anharmonic perturbation. In this work, we extend the proof and present a detailed derivation of Miller’s rule for an equivalent quantum-mechanical anharmonic oscillator. For this purpose, the classical concept of velocity-dependent damping inherent to the Lorentz model is replaced by an adiabatic switch-on of the external electric field, which allows a unified treatment of the classical and quantum-mechanical systems using identical potentials and fields. Although the dynamics of the resulting charge oscillations, and hence the induced polarizations, deviate due to the finite zero-point motion in the quantum-mechanical framework, we find that Miller’s rule is nevertheless identical in both cases up to terms of first order in the anharmonicity. With a view to practical applications, especially in the context of ab initio calculations for the optical response where adiabatically switched-on fields are widely assumed, we demonstrate that a correct treatment of finite broadening parameters is essential to avoid spurious errors that may falsely suggest a violation of Miller’s rule, and we illustrate this point by means of a numerical example.

Effects of gamma radiation on the optical properties of ultrafine iron particle/polystyrene composites

The present research studied the influence of gamma radiation doses on the optical properties and parameters of the tested composite samples consisting of polystyrene polymer as a matrix filled with different concentrations of ultrafine iron particles (0, 10, 20, and 30 wt.%) with an average thickness of 2 µm. Using a UV-1800 Shimadzu spectrophotometer, the optical absorbance and transmittance values of the tested composite samples were measured at room temperature in the wavelength range of 200–800 nm. Optical parameters such as the excitation energy for electronic transitions, optical energy gap, dispersion energy, static dielectric constant, static refractive index, moments of the optical spectrum, optical oscillator strengths, linear optical susceptibility, third-order nonlinear optical susceptibility, carrier concentration to the effective mass ratio, high-frequency dielectric constant, nonlinear refractive index, plasma frequency and long wavelength refractive index were calculated and discussed at different doses of gamma radiation (1, 2, and 6 kGy). The results demonstrate that the optical properties and parameters of the gamma-irradiated composites vary with increasing gamma doses. This variation in values was observed after increased irradiation due to enhanced metal–polymer bonding and due to an increase in the density of the free charges within the metal polymer composites.

The structure, morphology, and optoelectronic properties of silicon nanowires decorated with GaN and Ag for single nanowire solar cell applications

This study focuses on the synthesis of a single Si-nanowire solar cell decorated with gallium nitride and silver nanoplasmons. The Si-nanowires were grown using the CVD approach followed by the decoration of their surfaces with GaN and Ag using a polyol approach. The structure of the developed GaN@Si and Ag@Si core/shell quantum wires was studied using X-ray diffraction. The morphology was investigated using scanning and transmission electron microscopy. The oxidation states were emphasized using X-ray photoelectron spectroscopy. The GaN and Ag nanoplasmons cause a modulation of the bandgap energy of the Si NWs. The growth of GaN and Ag nanoplasmons on the surface of Si nanowires increases the charge carrier density, photocurrent, and optical hole mobility. The plasmonic Ag nanoparticles suppress the nonlinear optical susceptibility of the Si nanowire compared to GaN-decorated Si NWs. The combination of quantum confinement and plasmonic effects of the proposed Ag@Si heterostructure nanowires offers great energy absorption and highly efficient separation of photogenerated electron/hole pairs. The developed single Ag@Si nanowire heterostructure exhibits photoconversion efficiency larger than GaN@Si NWs by one order of magnitude and larger than the un-decorated Si nanowires by 20-fold.

Nonlinear Optical Refraction and Absorption Features of Methyl Orange Dye in Polar Solvents.

Herein, we report the nonlinear optical (NLO) refraction and absorption features of azo dye namely, methyl orange (MO) dissolved in ethanol, methanol, acetone, 1-propanol, DMF and DMSO. The UV-Visible absorption study reveals that the maximum absorption spectrum of MO dye appeared towards longer wavelength by increasing the solvent polarizability is the result of red shift or bathochromic shift. The Z-scan method is utilized to measure the third-order NLO features of MO dye in different polar solvents. A continuous wave laser with 5-mW power and an excitation wavelength of 405nm is employed in the Z-scan technique. The NLO features including nonlinear index of refraction (n2), nonlinear coefficient of absorption (β) and third-order NLO susceptibility (χ3) are calculated to be the order of 10-7 cm2/W, 10-2cm/W and 10-7 esu, respectively. The NLO index of refraction shows peak-valley transmittance is the result of self-defocusing and NLO absorption coefficient exhibits both positive and negative nonlinearity owing to saturable absorption (SA) and reverse saturable absorption (RSA). The effect of solvent polarizability and dipole moment on third-order NLO susceptibility of MO dye is discussed. Based on the experimental results, an azo dye MO appears to be a promising option for NLO applications in the future.

Influence of Polar Solvents on Third-Order Nonlinear Optical Features of Methyl Red Dye.

This study emphasis the solvent effect on third-order nonlinear optical (NLO) features of methyl red (MR) dye dissolved in polar solvents including ethanol, methanol, acetone, 1-propanol, DMF and DMSO using low power diode laser. Z-scan technique operating at 405nm wavelength, is used to estimate the third-order NLO features of MR dye in various solvents. The dye discloses self-defocusing nonlinear index of refraction (n2), which is determined to be the order of 10-7 cm2/W. The nonlinear coefficient of absorption (β) of MR dye displays both negative and positive value owing to saturable absorption (SA) and reverse saturable absorption (RSA), respectively. The real and imaginary components of the third-order NLO susceptibility of MR dye in polar solvents are measured to be the order of 10-6 esu and 10-7 esu, respectively. The dye exhibits a large NLO susceptibility in DMSO, which is estimated to be 1.21 × 10-6 esu. The effect of solvent spectral features on MR dye is determined by applying a multi-parameter scale called Kamlet-Abboud-Taft. The experiment results indicate that MR dye is a promising NLO material that may find applications in photonics and optoelectronics.

Third-order nonlinear optical susceptibility of hydrogenic impurity in Ge/Si0.15Ge0.85 spherical core/shell quantum dots under electric field

In this review, we have investigated theoretically the third-order nonlinear optical susceptibility in Ge/Si0.15Ge0.85 spherical core/shell quantum dots under electric field (EF) for both cases with and without on-center impurity within the framework of the compact-density-matrix (C.D.M). The eigenenergies and their corresponding wave functions of the system are computed by solving the three-dimensional Schrödinger equation using the effective mass approximation (E.M.A) using the variational method (VM). Our computational results show that both the energy levels and the third-order nonlinear optical susceptibility are strongly affected by the quantum dot size, the effects of the hydrogenic impurity, and the electric field intensity.

Optical and optoelectronic properties of gallium oxide films fabricated by the chemical vapour deposition method

The present work investigated the influence of growth time on the structural, optical, and optoelectronic properties of β-Ga2O3 films produced on Si substrates by the chemical vapour deposition method. The prepared films were characterized by X-ray diffraction, field-emission scanning electron microscope, and UV–Vis spectrophotometer. The films exhibited a mixed phase (β-α)-Ga2O3 crystal structure. The crystallite size ranged between 34.98 and 164.69 nm. The bandgap increased from 4.74 to 4.88 eV. The absorption and extinction coefficients were in the orders of 103 and 10−1, respectively. The refractive index, dispersive energy and single oscillator energy increased from 1.86 to 1.87, 19.24 to 28.64, and 8.36 to 9.54, respectively, with an increase of growth time. The oscillator strength, oscillator wavelength, third-order nonlinear optical susceptibility and dispersion of refractive index were in the orders of 10−4, 10−2, 10−10 and 10−9, respectively. The carrier concentration, optical conductivity, optical mobility, and optical resistivity were also evaluated. The real and imaginary dielectric constants, and plasmon frequency were also determined.