Order Nonlinear Susceptibility Research Articles

Enhanced Linear and Nonlinear Optical Characteristics of Cerium (Ce) Doped ZnO Film

ZnO and Ce-doped ZnO films with different doping concentrations (2, 4, and 6 wt%) were produced via SILAR technique, and the influence of the Ce amount on the structural, morphological, linear and nonlinear optical properties were examined in detail. Structural analyses conducted using X-ray diffraction (XRD) and Raman spectroscopy revealed the formation of hexagonal wurtzite pristine ZnO and Ce-doped ZnO nanostructures. The CeO2 phase was observed for only Ce6:ZnO samples by the XRD and Raman analyses. The morphological analyses were performed with a Scanning Electron Microscope (SEM), and it was found that the grain size decreased with Ce doping. The band gap energies decreased from 3.18eV to 2.67eV with increasing dopant (Ce) amount and increasing Urbach energy (EU). The dislocation density values (XRD) were calculated as 1.68x , 2.22x , 4.52x , and 8.65x nm-2 for ZnO, Ce2:ZnO, Ce4:ZnO, and Ce6:ZnO, respectively, which is consistent with the increasing Urbach energy. The optical characteristics such as excitation and absorption coefficient, refractive index, dielectric constant, optical conductivity, the volume (VELF) and surface (SELF) energy loss functions were estimated. The third- order nonlinear susceptibility, and the nonlinear refractive index were calculated using Miller's generalized rule with linear refractive index and Wemple-DiDomenico (W-D) model. The χ(3) and n2 values increased with Ce influence compared to undoped ZnO film. Various methods have been used to obtain Ce:ZnO films, but the low-cost SILAR method has not been reported before, and the films produced via this method showed suitable behaviours for optoelectronic devices and nonlinear applications.

Nonlinear optical properties of glassy TeO[formula omitted]: ab initio modeling of [formula omitted] and Hyper Raman spectra

The nonlinear optical properties of amorphous tellurium oxide is studied in a framework of computational technique based on the ab initio quantum-chemical calculations. The calculated values of refractive index and third-order nonlinear susceptibility are in a very good agreement with experimental data. The origin of the high nonlinear properties of TeO2 is attributed, in general, to the hyperpolarizability of Te atoms electron lone pairs and to the hyperpolarizability of electronic density localized on bonds of the asymmetric Te-O-Te bridges in part. The computational technique is extended on Hyper Raman spectroscopy including scattering on longitudinal modes. The spectra was calculated for both crystalline and glassy TeO2 with a very good reproduction of experimental data. An extra bands inactive in classical Raman spectroscopy is studied using this aproach. The most intense high-frequency band in the spectra of paratellurite is attributed to anti-symetric stretching of long-short bonds in TeO4 disphenoid with A2 symmetry. The influence of the structural unit configuration on the band position in Hyper Raman spectra is established. The best agreement between calculated phonon spectrum and experimental data is obtained using hybrid functional approach, which explains strong correlation on valence electron states of Te atoms. The strong dependence of LO modes intensity in Hyper Raman spectra on third order nonlinear susceptibility is obtained and explained. The reported technique can be easily extended on a big family of binary and ternary compounds.

Growth of L-asparagine monohydrate organic single crystals: An experimental and DFT computational approach for nonlinear optical applications

Good optical quality of L-asparagine monohydrate (C4H8N2O3.H2O) organic single crystal has been grown by adopting natural slow evaporation process at room temperature from aqueous solutions. The lattice parameters obtained by powder X-ray diffraction data revealed orthorhombic crystal system of the harvested crystal. The morphology and planes of the crystal have been identified. The molecular vibrations and functional groups have been specified by Fourier transform infrared (FTIR) spectroscopy studies. Energy dispersive X-ray (EDX) study has been availed to find out the elements constituting the crystal. Scanning electron microscopy, (SEM), provided the surface morphology of the crystal. The dependence of dielectric properties on frequency and temperature have been investigated and the electronic polarizability (α) has been determined. UV–vis spectral analysis shows that the crystal possesses good optical transmittance in the visible part of the energy spectrum. The optical band gap and the Urbach energy have been determined from lower absorption edge. Third order nonlinear susceptibility χ(3), nonlinear refractive index (n2), and linear susceptibility χ(1) have been calculated by Miller's generalized rule. The first-principle computation of band structure of electrons and the electron density of states have been discussed, which suggest that the crystals possess direct band gap. Density Functional Theory (DFT) with B3LYP function by Gaussian09W software was utilized to calculate HOMO-LUMO energy gap as well as non-linear optical parameters namely, linear polarizability (α), hyperpolarizability (β and γ) and dipole moment (μ) of L-asparagine monohydrate crystal. All the findings prove that L-asparagine monohydrate is a promising NLO crystal.

Nonlinear optical parameters and electronic properties of plasma polymerized methyl acrylate thin films

Plasma polymerized methyl acrylate (PPMA) thin films were fabricated on a borosilicate glass substrate at a plasma power of 28 W to study nonlinear optical parameters and electronic properties. X-ray Diffraction analysis confirmed the amorphous nature of the PPMA films, while Attenuated total reflectance Fourier transform infrared spectroscopy indicated monomer fragmentation due to plasma polymerization. Field emission scanning electron microscope images of the films display a water wave-like structure. PPMA films demonstrated thermal stability up to approximately 574 K in both N2 and air environments. The values of direct band gap energies increase from 3.30 to 3.41 eV with increasing film thicknesses, whereas the Urbach energy values show in an opposite manner. The Wemple-DiDomenico model was employed to analyze both the oscillator energies ranging from 5.54 to 6.44 eV and the dispersion energies ranging from 10.56 to 12.89 eV. The static linear refractive index showed typical dispersion behavior, with film thickness conforming to Moss's rule. The nonlinear refractive index and 2nd and 3rd order nonlinear susceptibilities decrease with increasing the studied films. The lattice dielectric constant values exceeded the high-frequency dielectric constant, indicating the presence of lattice vibrations and free carriers. Electronic parameters are fluctuating with increasing film thickness. The observed changes in nonlinear optical parameters and electronic properties highlight the potential of PPMA films for applications in photovoltaic and optoelectronics.

Second harmonic generation at a time-varying interface

Time-varying metamaterials rely on large and fast changes of the linear permittivity. Beyond the linear terms, however, the effect of a non-perturbative modulation of the medium on harmonic generation remains largely unexplored. In this work, we study second harmonic generation at an optically pumped time-varying interface between air and a 310 nm Indium Tin Oxide film. We observe a modulation contrast at the second harmonic wavelength up to 93% for a pump intensity of 100 GW/cm2, leading to large frequency broadening and shift. We experimentally demonstrate that a significant contribution to the enhancement comes from the temporal modulation of the second order nonlinear susceptibility. Moreover, we show the frequency-modulated spectra resulting from single and double-slit time diffraction could be exploited for enhanced optical computing and sensing, enabling broadband time-varying effects on the harmonic signal and extending the application of Epsilon-Near-Zero materials to the visible range.

New insights into non-linear optical properties, photocatalytic activity, and applications of ZnSe:Cu nanoparticles prepared by microwave-assisted hydrothermal method

In the present work, semiconducting ZnSe:Cu (0, 0.1, 0.75, 1.5, 2.25 and 3 mol%) nanoparticles (NPs) were prepared by microwave-assisted hydrothermal (MAH) method at the fixed pH of 11.2. XRD patterns certified the formation of nanocrystals with the size of about 2.04–2.21 nm. Also, FESEM and TEM images confirmed the formation of round-shape NPs. UV–Vis spectra showed that the energy gap of nanoparticles decreased from 3.615 to 3.342 eV by the increment in copper impurity content. The exact value of the energy gap of NPs was determined by the absorption spectrum fitting derivative method (DASF). Results revealed that these NPs have a high potential in optical and optoelectronic applications; specially, the samples owing 1.5 and 2.25 mol% of Cu-impurity, as the best candidates for optical fiber applications, showed the highest third order non-linear optical susceptibility (χ(3)). Also, for all synthesized NPs, the optical characteristics such as the optical transition index (m), Urbach energy (Etail), dielectric constant (ε) and the refractive index (n) at the absorption edge were determined. Moreover, the amount of metallization factor was also calculated, which decreases with the increase of impurity and microwave irradiation, indicating the increase of metal affinity of the samples. Photoluminescence (PL) spectra of ZnSe NPs demonstrated a general reduction in the intensity upon the introduction of Cu. This anticipated quenching further supports their heightened photocatalytic activity. The results of photocatalytic tests indicate that the sample containing 2.25 mol% of Cu exhibits the highest rate constant value (0.0255 min−1) and achieves the maximum efficiency (75.7 % after 60 min) for degrading the DB71, establishing it as the prime candidate for photocatalytic applications.

Investigation on Physicochemical Properties of Nonlinear Optical (NLO) Single Crystal: Rubidium Hydrogen Fumarate

A solvent evaporation method produced an optically high-quality semiorganic single crystal of Rubidium hydrogen fumarate (RbHF) at room temperature. The structural analysis reported that the RbHF crystallized in triclinic crystal system with centrosymmetric space group P1¯. The Powder XRD pattern indicates the grown crystal have good crystalline nature. FTIR spectroscopy examined the functional group and bonding in the grown molecule. A optical transparency of about 88% were observed in RbHF and having energy bandgap of 3.9 eV were calculated using Tauc’s plot. The grown crystals were thermally stable upto 170°C. Mechanical and dielectric analysis has been carried and their properties were discussed in detail. Intermolecular interactions were studied using Hirshfeld surface maps and 2D fingerprint plots. The grown crystal have positive photoconductivity nature. A Z-scan were used to study the third order NLO response in RbHF crystal. The third order nonlinear susceptibility of RbHF crystal was estimated as (χ3) = 1.60244 × 10-08 esu, nonlinear absorption coefficient (β) = 6.39395 × 10-5 cm2/W and nonlinear refractive index (n2) = 9.15822 × 10-12 cm/W. The observed results of the RbHF single crystal show, it has the potential application in optical and optoelectronic devices.

Innovative synthesis, structural characteristics, linear and nonlinear optical properties, and optoelectric parameters of newly developed A2ZnGeO4 (A = K, Li) thin films.

The synthesis of high-quality thin films through spin coating deposition on meticulously cleaned glass substrates is presented. Optical band gaps E g of both samples using the Kubelka-Munk function are determined. The data analysis uncovers the presence of optical allowed direct transition for A2ZnGeO4 (A = K, Li). Spectroscopic ellipsometry measurements on A2ZnGeO4 (A = K, Li) thin films and an analysis of their optical properties using the Cauchy model are presented. Furthermore, the increase of the thickness of the thin film results in improvements in their optoelectrical parameters, such as electrical conductivity, optical mobility, and optical conductivity. Using the Kubodera and Kobayashi comparative model, the third order nonlinear susceptibility (χ (3)) was estimated based on the compounds' high linear absorption of the generated third harmonic wavelength (355 nm). This paper presents remarkable NLO results that reveal potential uses in optoelectronics and photonics.

Integration of conventional surface science techniques with surface-sensitive azimuthal and polarization dependent femtosecond-resolved sum frequency generation spectroscopy.

Experimental insight into the elementary processes underlying charge transfer across interfaces has blossomed with the wide-spread availability of ultra-high vacuum (UHV) setups that allow the preparation and characterization of solid surfaces with well-defined molecular adsorbates over a wide range of temperatures. Within the last 15 years, such insights have extended to charge transfer heterostructures containing solids overlain by one or more atomically thin two dimensional materials. Such systems are of wide potential interest both because they appear to offer a path to separate surface reactivity from bulk chemical properties and because some offer completely novel physics, unrealizable in bulk three dimensional solids. Thick layers of molecular adsorbates or heterostructures of 2D materials generally preclude the use of electrons or atoms as probes. However, with linear photon-in/photon-out techniques, it is often challenging to assign the observed optical response to a particular portion of the interface. We and prior workers have demonstrated that by full characterization of the symmetry of the second order nonlinear optical susceptibility, i.e., the χ(2), in sum frequency generation (SFG) spectroscopy, this problem can be overcome. Here, we describe an UHV system built to allow conventional UHV sample preparation and characterization, femtosecond and polarization resolved SFG spectroscopy, the azimuthal sample rotation necessary to fully describe χ(2) symmetry, and sufficient stability to allow scanning SFG microscopy. We demonstrate these capabilities in proof-of-principle measurements on CO adsorbed on Pt(111) and on the clean Ag(111) surface. Because this setup allows both full characterization of the nonlinear susceptibility and the temperature control and sample preparation/characterization of conventional UHV setups, we expect it to be of great utility in the investigation of both the basic physics and applications of solid, 2D material heterostructures.

Growth of L asparagine monohydrate doped potassium dihydrogen phosphate semiorganic crystals and its structural, thermal and optical properties

A novel semiorganic crystal is harvested by doping organic amino acid L asparagine monohydrate (LAM) with inorganic compound Potassium dihydrogen phosphate (KDP) by adopting slow evaporation method. Rietveld refinement of the XRD data was performed and the structural study exhibits single phase nature of the LAM doped KDP (LAM-KDP) crystals with a slight decrease in c-axis of the unit cell parameters. Other crystallographic parameters such as crystallite size and strain were also evaluated. The interaction of LAM with KDP was studied from FT-IR analysis by detecting functional groups. The constituting elements of the crystal were identified by energy dispersive X-ray (EDX) analysis. Etching study has been employed to study surface morphology of these crystals. From UV–vis transmittance data, optical band gap and different optical constants like Urbach energy, dielectric constants, electrical and optical conductivities were evaluated. Optical transparency of the LAM-KDP crystals is observed to increase. The third order nonlinear susceptibility χ(3) and nonlinear refractive index n2 of the grown crystals have been predicted using empirical Miller's rule. The value of χ(3) has increased from 1.87 × 10−13 esu to 4.29 × 10−13 esu due to LAM doping. Change in enthalpy (ΔH), change in Gibb's free energy (ΔG) and activation energy Ea during chemical reaction were calculated by thermogravimetric analysis (TGA). Thermal decomposition characteristics of the crystals were analyzed by differential scanning calorimetry (DSC). The high transparency of LAM-KDP crystals in the entire visible spectrum and larger values of nonlinear susceptibility χ(3) and nonlinear refractive index n2 make the synthesized crystal applicable for NLO and optoelectronic devices applications.

Studies of chemical bonds loss and optical modifications of CR-39 caused by gamma rays

The induced impacts of high doses of gamma irradiation on the structural variations of poly-allyl-diglycol carbonate (PADC) polymers (CR-39) were studied in terms of X-ray diffraction (XRD) patterns. CR-39 samples were irradiated separately at different ranging from 200 to 800 kGy; (step 200). A deconvolution process of the XRD spectra of CR-39 samples for all gamma irradiation doses was performed. The results of this deconvolution process for the pristine specimen show three diffraction peaks at about 20.30°, 28.16° and 41.70° of 2θ. The broad peaks at 28.16o and 41.70°, and the highest peak at 20.30° of XRD confirm the amorphous nature and low degrees of crystallinity, respectively. The position, area, intensity and full width at half maximum of these peaks are changed with further doses of gamma irradiation. With additional gamma irradiations, the intensities of all peaks decrease significantly. The highest and sharpest peak properties are employed to determine the crystallinity, crystallite size, and radiation chemical yield (G-value) for the loss of carbonate ester bonds using a proposed method. Higher doses of gamma irradiation result in a decrease in crystallinity while increasing crystallite size. Furthermore, the optical band gaps reduced from 4.81 to 3.49 eV when the irradiated dose increased from 0 to 800 kGy. Furthermore, the third order nonlinear susceptibility increased from 0.84x10−12 esu to 2.25x10−12 esu with increasing the radiation doses from 0 to 800 kGy. Moreover, the nonlinear refractive increased from 1.52x10−11 to 3.69x10−11 with increasing the radiation doses from 0 to 800 kGy. On the other hand, the number of carbon atoms in each cluster increased from 51 to 97 when the irradiated dose increased from 0 kGy to 800 kGy.

Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study.

We present a theoretical investigation of guided second harmonic generation at THz frequencies in SiGe waveguides embedding n-type Ge/SiGe asymmetric coupled quantum wells to engineer a giant second order nonlinear susceptibility. A characteristic of the chosen material system is the existence of large off-diagonal elements in the χ 2 tensor, coupling optical modes with different polarization. To account for this effect, we generalize the coupled-mode theory, proposing a theoretical model suitable for concurrently resolving every second harmonic generation interaction among guide-sustained modes, regardless of which χ 2 tensor elements it originates from. Furthermore, we exploit the presence of off-diagonal χ 2 elements and the peculiarity of the SiGe material system to develop a simple and novel approach to achieve perfect phase matching without requiring any fabrication process. For a realistic design of the quantum heterostructure we estimate second order nonlinear susceptibility peak values of ∼7 and ∼1.4 × 105 pm/V for diagonal and off diagonal χ 2 elements, respectively. Embedding such heterostructure in Ge-rich SiGe waveguides of thicknesses of the order of 10-15 μm leads to second harmonic generation efficiencies comprised between 0.2 and 2 %, depending on the choice of device parameters. As a case study, we focus on the technologically relevant frequency of 7.1 THz, yet the results we report may be extended to the whole 5-20 THz range.

Investigation on the growth aspects and properties of rubidium hydrogen succinate hydrate single crystal for NLO applications.

A novel semiorganic nonlinear optical single crystal of rubidium hydrogen succinate hydrate (RbHSH) was grown at room temperature using the slow evaporation solution growth technique (SEST) with water as a solvent for nonlinear optical applications. The grown crystal is a triclinic system with a centrosymmetric space group of P1̄ and the compound is stabilized by intramolecular O-H-O and C-H-O bonding. FTIR spectral studies were used to determine the various functional groups present in the material. The optical transmission spectra of the grown crystal demonstrated that a transparency of 89%, with a low cut off wavelength of 240 nm and an energy band gap of 5.21 eV, which is beneficial to developing advanced photonic and optoelectronic devices in the solar blind UV area. The grown crystal is thermally stable upto 174 °C. The electrical properties of RbHSH crystal exhibit low dielectric loss and a low dielectric constant at high frequencies tends to have good optical characteristics. Mechanical analysis demonstrated that the grown crystal shows the normal indentation size effect (ISE) and falls into the hard material category with n = 1.4. Photoconductivity measurements revealed negative photoconductivity. Photoluminescence studies showed that RbHSH emits blue light with a wavelength of 484 nm. Hirshfeld surface analysis was used to analyze intermolecular interactions in the RbHSH crystal. The grown RbHSH crystal piezoelectric charge coefficient have been calculated (d33 = 13 pC N-1) and it is suitable for piezoelectric device applications. Under continuous-wave laser excitation, the third order nonlinear refractive index (n2), absorption coefficient (β), and susceptibility (χ(3)) of the RbHSH crystal were found to be 1.6639 × 10-12 (cm2 W-1), 1.1739 × 10-5 (cm W-1) and 4.86331 × 10-9 esu, respectively.

Effect of thermal poling in sodium tantalum phosphate glass-ceramics

Eu3+-doped sodium tantalum phosphate glass-ceramics containing bronze -like perovskite crystalline phase Na2Ta8O21 were obtained with different crystalline states (degree of crystallinity and average crystallite size) by a suitable control of the heat-treatment time and temperature of the precursor glass. Luminescence properties of Eu3+ in these materials are in agreement with a progressive insertion of the rare earth ions in the sodium tantalate Na2Ta8O21 phase, as probed by a clear decrease of the intensity ratio between transitions [5D0 →] 7F2/7F1 and narrowing of characteristic emission bands. Thermal poling insights were performed on these glassy and glass-ceramic materials and the experimental conditions had to be carefully optimized in the glass-ceramics to avoid electrical sparks and sample break associated with dielectric breakdown of the samples. Suitable and stable thermal poling treatments could be performed at 250 °C and 900 V under N2 atmosphere on both glass and glass-ceramics. These first insights pointed out a lower migration kinetic of sodium ions when compared to the precursor glass as well as a lower content of depleted ions, since part of sodium is supposed to be “frozen” inside the crystalline phase in glass-ceramics. Despite these lower kinetic poling conditions, a poled sodium depleted layer whose thickness depends on the poling time was successfully formed at the anode side. Reflectance infrared spectroscopy was also used to investigate the structural changes in the poled layer. These IR data pointed out that structural changes induced by thermal poling are mainly promoted in the phosphate network rather than tantalate units in both glass and glass-ceramics in agreement with a selective sodium migration from the remaining glassy phase. Macroscopic induced SHG measured by the Maker fringes technique is also consistent with the EFISH model and quantitative simulations of these data allowed to estimate second order nonlinear optical susceptibilities χ(2) ten to twenty times lower in the glass-ceramics than in the precursor glass. Such electric behavior is discussed in terms of dielectric properties of heterogeneous materials and interfacial polarization mechanisms between crystallites and glassy phase.

Effects of the magnetic field and the off-center displacement on the third-order nonlinear optical susceptibility of inverted core/shell spherical one-electron quantum dots

The third order nonlinear optical susceptibility (TONOS) of an inverted ZnS/CdSe core–shell spherical quantum dot embedded in SiO 2-matrix with or without impurity, and subjected to an external magnetic field is investigated. Within the framework of effective mass approximation and using B-splines basis functions, the energy levels, the dipole matrix elements and the TONOS are computed. The dielectric mismatch in the interface dots as well as the effective mass dependence on the core and shell regions are taken into account. It is revealed that, simultaneously the shell size, magnetic field and off-center displacement have a noticeable effect on the positions and the heights of the peaks of the TONOS. Moreover, we have shown that, due to the magnetic field and the off-center displacement effects, the TONOS takes different profiles associated with the polarization direction (parallel and perpendicular). In the perpendicular polarization, two peaks of the nonlinear optical properties appear for each off-center displacement value corresponding to the two transversal allowed transitions. The shift towards higher energies of the peak position and the reduction of the intensity of the peak when the magnetic field increases are recorded in the transversal transition case. Furthermore, in the longitudinal transition, as increasing the magnetic field strength, the intensity of the peak of the TONOS grows and the position of the peak is shifted towards lower frequencies. The dielectric constant, effective mass and conduction band offset of the materials that constitute the core and shell are equally found to modify significantly the main features of the susceptibility.

Physicochemical factors that enhance the third order nonlinear susceptibility χ(3) in nitroanilines and conjugated polyenyne polymers with arylamine substituents

This work analyzes the physicochemical factors that improve the χ(3)-NLO properties based on Hückel-Agrawal’s model. The model compounds are the nitroanilines ortho o-NA, meta m-NA, and para p-NA, and the aromatic polyenynes with phenyl and an NH2 group in position ortho, meta, and para, or without the amine group. We analyze the correlation effects, the dipole moments, the resonance energy, the frequency of the laser wavelength, the interband and intraband effects, the charge density, the curvature of the dipole moments, and the vibration phononic factor in addition to the molecular effects proposed by Nalwa’s work. Then, we have found, for example, that the addition of a conjugate chain to the nitrogen of the amine, the continuity of the same sign of charge in the valence band, which produces electric repulsion, or the increase in the spatial asymmetry of the groups attached to the aromatic ring can increase the χ(3) values.

STUDY OF GLASS FORMERS ON BASICS OF OPTICAL ELECTRONEGATIVITY

Concept of electronegativity is used by so many researchers to study Refractive index, Band energy, Dielectric constant, Metallization criterion, Basicity, Oxide ion polarizability, Bond ionicity, Third order non-linear optical susceptibility to study so many glass systems. Here the concept of optical electronegativity is used to study these parameters in glass formers. It is observed that on decreasing the values of optical electronegativity; optical band energy, metallization criterion, and bond ionicity decreases; where as optical dielectric constant, optical basicity, oxide ion polarizability refractive index and third order non linear optical susceptibility increases. All glass forming oxides are according to Pauling's packing rule, Goldschmidt radius ratio rule, Zachariasen's random network theory and rules for formation of glass and Sun’s single bond strength theory. For glass formers radius ratio rc/ra = 0.14-0.40, [except P2O5] and single bond strength greater than 90 Kcal/mol. Key Words: Band energy, Basicity, Optical dielectric constant, Oxide ion polarizability, Refractive index.

Study of Conditional Glass Formers (II) on Basics of Optical Electronegativity

Concept of Electronegativity is used by so many researchers to calculate Refractive index Band energy, Dielectric constant, Metallization criterion, Basicity, Oxide ion polarizability, Bond ionicity, Third order non-linear optical susceptibility to study the so many glass systems. Here the concept of optical electronegativity is used to study these parameters for conditional glass formers refer as (II) of group V(A,B) and VI(A,B). They are Ta2O5, Nb2O5, V2O5, Cr2O3, Bi2O3, TeO2, MoO3, As2O3, WO3, Se2O3. It is observed that on decreasing the values of optical electronegativity, optical band energy, metallization criterion, and bond iconicity decreases; and optical dielectric constant, optical basicity, oxide ion polarizability refractive index, third order non linear optical susceptibility increases. All conditional glass forming oxides (II) are according to Pauling's packing rule, Goldschmidt radius ratio rule, Zachariasen's random network theory and rules for formation of glass and Sun’s single bond strength theory. For Conditional glass formers (II) radius ratio rc/ra = 0.250-0.492, [except Bi2O3 (0.75) & TeO2 (0.87)] and single bond strength greater than 90 Kcal/mol. According to Sun’s, high bond strength oxides are not good glass formers because they themselves do not forms glass; but when they forms small ring in the melt of these materials which would result in easy crystallization. Key Words: Refractive index Band energy, Dielectric constant, Metallization criterion, Basicity, Oxide ion polarizability, Bond ionicity, Third order non-liner optical susceptibility.

Study of Conditional Glass Formers (I) on Basics of Optical Electronegativity

Concept of Electronegativity is used by so many researchers to calculate Refractive index, Band energy, Dielectric constant, Metallization criterion, Basicity, Oxide ion polarizability, Bond ionicity, Third order non-linear optical susceptibility to study the so many glass systems. Here the concept of optical electronegativity is used to study these parameters for conditional glass formers referred as (1) taken from group III (A,B) and IV (A,B); they are Y2O3, HfO2, ZrO2, Sc2O3, TiO2, Al2O3, In2O3, Ga2O3, and SnO2. It is observed that optical band energy, metallization criterion, and bond iconicity decreases; and optical dielectric constant, optical basicity, oxide ion polarizability refractive index and third order non linear optical susceptibility increases. All conditional glass formers (I) oxides are according to Pauling's packing rule, Goldschmidt radius ratio rule, Zachariasen's random network theory, rules for formation of glass and Sun’s single bond strength theory. For conditional glass formers (I) radius ratio rc/ra = 0.40-0.75 and single bond strength greater than 90 Kcal/mol. According to Sun’s, high bond strength oxides are not good glass formers because they themselves do not forms glass; but when they forms small ring in the melt of these materials which result in easy crystallization. Key Words: Refractive index Band energy, Dielectric constant, Metallization criterion, Basicity, Oxide ion polarizability, Bond ionicity, Third order non-liner optical susceptibility.

Effect of TiO2/ZnO nanofillers on structural, optical and nonlinear optical properties of PVA

Polyvinyl alcohol (PVA)/(x)Titanium dioxide (TiO2) (15-x) Zinc oxide (ZnO) nanocomposites for x = 0, 1, 5, 7.5, 10, 14 and 15 wt% concentration was prepared using solution casting method with the help of an ultrasonicator. The XRD spectra of films validate the formation of nanocomposites, as evidenced by the presence of peaks corresponding to both PVA and TiO2/ZnO nanoparticles. FTIR spectroscopy reveals the formulation of complexes between the PVA main chain and nano fillers. The homogeneous distribution of nano fillers in PVA nanocomposites was observed using SEM and EDAX. The optical studies conducted using an ultraviolet–visible spectrometer reveals that PVA/(x)TiO2(15-x) ZnO shows minimum energy gap of 2.66 eV at x = 15 wt%. The photoluminescence measurements carried out at an excitation wavelength of 370 nm using spectrophotometer exhibits unique strong emission band at 680 nm in the visible region for all the films. The open aperture (OA) Z-scan traces of PVA filled TiO2–ZnO nanocomposites at various filling levels were explored by means of Z-scan technique with DPSS continuous wave laser at 532 nm wavelength and 200 mW output power reveals that the absorption coefficient (β) of PVA nanofilms rises from 3.19 × 10−5 cm/W (for pure) to 1.17 × 10−3 cm/W (for x = 14 wt %) with rise in filling level. The closed-aperture (CA) z-scan analysis gives the nature of third order nonlinear refractive index (NRI) (n2) of PVA nanofilms. The value of nonlinear refractive index (NRI) increases from −1.57 × 10−9cm2/W (pure PVA) to −3.24 × 10−8 cm2/W for x = 14 wt% filling level. The observed enhancement in Nonlinear absorption (NLA) coefficient (β), NRI (n2) and third order nonlinear susceptibility (χ3) of prepared nanocomposites is due to added nanofillers to the PVA matrix. The improved third order nonlinear optical properties make these PVA nanocomposites as good candidates for optical switching device and optoelectronic device applications.