Nonlinear Refractive Index N2 Research Articles

Synthesis, Structural, Spectroscopic and Quantum Chemical Investigation of a Novel 1,4-Diamino-2,5-dichlorobenzenium Picrate Single Crystal: An Efficient NLO Material

A new organic nonlinear optical single crystal, 1,4-diamino-2,5-dichlorobenzenium picrate (DADCBP) has been successfully grown by solvent slow evaporation method. DADCBP crystallizes in a triclinic structure with the centrosymmetric space setup, P-1. The molecular structure of the grown crystal has been determined by NMR spectral analysis. The existence of discrete functional branches of the crystal has been identified by FTIR spectral study. The optical property of the title crystal has been measured by UV-Vis-NIR spectral analysis. PL spectra reveal the emission bands of the grown crystal. The thermal stability of the harvested crystal has been examined by the TG/DTA study. The dielectric constant and loss have been taken to locate the arrangement of charges in the grown crystal. The quantum chemical studies have been performed to analyze the HOMO/LUMO, molecular geometry, and mulliken atomic charge by B3LYP at the 6-311++G (d,p) level of theory. H···H, O···H, C···H, C···C various intermolecular interactions of hydrogen bonds in the DADCBP molecule have been visualized by the Hirshfeld surface analysis. The nonlinear optical (NLO) characteristics like nonlinear absorption coefficient (β), nonlinear refractive index (n2) and susceptibility (χ(3)) have been examined using the Z-scan technique.

Large third-order nonlinear susceptibility of newly synthesized 3-amino-1H-1,2,4-triazolium p-toluene sulfonate (TPTSA) single crystal measured by the open and closed aperture of the Z-scan technique

The researchers employed the Slow Evaporation Solution Technique (SEST) to grow a third-order nonlinear optical 3-amino-1H-1,2,4-triazolium p-toluene sulfonate (TPTSA) crystal and subsequently conducted an X-ray structural examination. The resulting solution's monoclinic structure (P21/c space group) was confirmed and refined using the SHELXS 2018/3 program, and this marks the first instance of a TPTSA single-crystal structure being reported. To further investigate the optical qualities of the TPTSA crystals, including reflectance (R), bandgap (Eg), refractive index (n), and extinction coefficient (K), we utilized a UV–Vis–NIR spectrophotometer, which demonstrated a transmittance of 82%. Moreover, photoluminescence spectrum analysis revealed that the crystal emits light at 294 and 471 nm. Thermal properties of the TPTSA single crystals were also studied, and it was determined that TPTSA remains stable up to 197 °C. A Hirshfeld surface study showed various inter and intra molecular interactions within the TPTSA compound. Based on the crystal's Z-scan parameters, such as absorption coefficient (β = 1.02412 × 10−4 m/W), nonlinear refractive index (n2 = 9.7348 × 10−12 m2/W), and third-order linear optical susceptibility (χ3) of TPTSA, which was found to be 3 × 10−8 esu, it is evident that the nonlinear properties of this crystal make it suitable for third harmonic generation applications. The comprehensive structural analysis and physical characteristics of the TPTSA crystal demonstrate its potential for applications in harmonic generation.

Effects of Mn doping on the structural, linear and nonlinear optical properties of Gd2O3 nanoparticles

We report on the effects of Mn doping on the structural, linear, and nonlinear optical properties of Gd2-xMnxO3 nanoparticles (x = 0.00, 0.03, 0.05, and 0.10). The Gd2-xMnxO3 powders were prepared using sol-gel process. The x-ray diffraction technique shows that the Mn3+ doping results in a small decrease in lattice parameter and an increase in crystallite size. UV–visible measurements were carried out in the wavelength range of 200–800 nm. The direct optical band gap estimated using Tauc model decreases with increasing Mn content from 5.152 to 5.008 eV, while Urbach energy increases from 0.753 to 1.012 eV. Moreover, the insertion of Mn results in a significant enhancement in the optical parameters (refractive index, extinction coefficient, absorption coefficient, dielectric constants (ε', ε"), optical and electrical conductivity. The dispersion energy (Ed) increases from 24.13 to 30.1 eV, while the single oscillator energy (E0) declines lightly from 10.28 to 9.998 eV with the increase of Mn content. With Mn doping an enhancement in the static linear refractive index (n0) and high-frequency dielectric constant (ε∞) were also observed. Analysis of linear and nonlinear optical parameters shows that the presence of manganese enhanced the linear optical susceptibility (χ(1)), third-order non-linear susceptibility (χ(3)), and non-linear refractive index (n2). These optical results show the potential applications of Gd2-xMnxO3 nanoparticles (x = 0.00, 0.03, 0.05 and 0.10) in various optical devices.

Third order nonlinear investigations of CuLaSe2 and ZnCuLaSe2 quantum dots

Environmentally friendly quantum dots (QDs) with high two-photon absorption coefficients in the near-infrared region are important for nonlinear optics (NLO) applications. In this work, CuLaSe2 and ZnCuLaSe2 QD are successfully synthesized and characterized using UV–Vis, Photoluminescence and HRTEM analysis. Next, the third-order NLO properties of these materials are studied using the femtosecond Z-scan method. The samples showed efficient nonlinear responses. The nonlinear absorption coefficient (β), the nonlinear refractive index (n2) and the third-order nonlinear susceptibility (χ(3)) values for all samples are deduced and discussed in detail. The results reported here pave the way towards building CuLaSe2 and ZnCuLaSe2 QDs-based nonlinear photoelectric devices operating in the near-infrared field.

Phase-change-driven tuning of linear and nonlinear optical properties of Te/As2Se3 bilayer thin films for optoelectronic applications

The present work reports the amorphous-crystalline phase transformation by interdiffusion of Te into the As2Se3 matrix with annealing at various temperatures (100, 150, and 200 °C). Te/As2Se3 bilayer thin films were prepared by electron beam evaporation under high vacuum conditions. The amorphous nature of As2Se3 thin film was confirmed from the X-ray diffraction study. The presence of small peaks in Te/As2Se3 thin film indicates the As4Te4 (monoclinic) and As2Se3 (monoclinic) phases, confirming the amorphous to crystalline phase transformation upon Te interdiffusion and subsequent annealing. The impact of Te top layer deposition on the vibrational modes were also observed from the Raman spectroscopy. The formation of Te agglomerates is confirmed from the morphological analysis which disappeared with further annealing. Furthermore, the water contact angle measurements have provided insight into surface interaction mechanisms of these materials. The linear and nonlinear optical properties were changed upon interdiffusion of Te as observed from UV–Visible spectroscopy. The increase in Eu indicated an increase in disorder hence the decrease in the bandgap. The 3rd order nonlinear susceptibility (χ3) and nonlinear refractive index (n2) increased with annealing. The tuning of linear and nonlinear optical properties by annealing can be used in various optoelectronic applications. Specifically, the phase transformation behaviour of Te/As2Se3 bilayer thin films enables their utilization in phase-change material-based optoelectronic devices.

Manufacturing-Enabled Tunability of Linear and Nonlinear Epsilon-Near-Zero Properties in Indium Tin Oxide Nanofilms.

Epsilon-near-zero (ENZ) materials have attracted great interest due to their exotic linear and nonlinear responses, which makes it significant to tune ENZ wavelengths for wavelength-dependent applications. However, studies to achieve tunability in a wide spectral range and link the fabrication parameters with linear and nonlinear ENZ properties have been uncovered. ENZ indium tin oxide (ITO) nanofilms are fabricated by magnetron sputtering, through which the control of ENZ properties is demonstrated. Factors in the sputtering process, such as the gas ratio and annealing, have a great impact on the ITO samples. Tunable ENZ parameters are listed to provide a beneficial database for ENZ ITO, mainly attributed to the change of carrier concentration. The influence of ENZ parameters on optical characteristics via annealing treatment is further explored. The ENZ wavelength is blue-shifted by 609 nm, and the intrinsic loss is reduced by 63.2%, while the ITO samples exhibit better linear scattering properties and stronger field intensity enhancement. Additionally, the laser testing system illustrates the change from reverse saturable absorption to saturable absorption with an absolute modulation depth of 21.9%, improved by 222.1%, and the nonlinear refractive index n2 and nonlinear absorption coefficient β are 2.07 × 10-16 m2 W-1 and -3.16 × 10-10 m W-1 for post-annealed ITO samples, respectively. The proposed sputtering protocol offers a feasible technique to control the linear and nonlinear ENZ performance, which has great potential in laser technology and nanophotonics.

Structural, magnetic, and nonlinear optical properties of calcium doped Ni-Zn ferrite nanoparticles synthesized by co-precipitation method

Ni0.5Zn0.45Ca0.05Fe2O4 nanoparticles were synthesized by co-precipitation technique, and its structural, spectroscopic, magnetic, linear, and third-order nonlinear optical characteristics were studied using XRD, Raman, and FTIR spectroscopy, VSM, UV–visible DRS spectroscopy, and z scan technique respectively. The XRD results revealed the inverse cubic (Fd3m) spinel structure and an average crystallite size of 36 nm. X-ray density, specific surface area were calculated, and the Rietveld refined parameters almost agree with the estimated structural parameters. FESEM images show spherical morphology and EDX analysis gives the chemical composition of the sample. A bandgap of 1.85 eV is found from the UV–Vis-DRS spectrum. The third-order nonlinear optical parameters such as nonlinear refractive index (n2), nonlinear absorption coefficient (β), third-order susceptibility (χ(3), second-order hyperpolarizability, and optical limiting response were studied with 532 nm 5 ns laser pulses. The synthesized nano compound had significant optical limiting property.

Enhanced nonlinear optical response by strong coupling between plasmonic antenna arrays and epsilon-near-zero film

A coupled structure of center-symmetric orthogonal nano-antenna arrays on fluorine-doped tin oxide (FTO) is designed to enhance the nonlinear response by the strong coupling. Further, we study the roles of structural and material parameters in determining the linear and nonlinear optical response of antenna-FTO metasurface. This structure shows broadband spectrum (∼900 nm) and large nonlinearity with nonlinear refractive index n 2 of 1.02 cm2/GW, which is about 400 times higher than that of bare FTO film. The results provide a promising platform for the realization of ultracompact and large nonlinear optical devices.

Studying the Symphonizing Effect of NLO Properties in Hydrated and Non-hydrated Donor Acceptor Complexes Formed Via Charge Transfer.

The present work intended to report the synthesis of newly designed donor-acceptor complexes of the pyrimidine-based system namely TAPHIA 1 and TAPHIA 2, which are symphonized to give the NLO properties. The methodologies adopted for both complexes were different and hence influenced their geometrical properties. The synthesized complexes were characterized using different techniques including SCXRD, FTIR, UV, PXRD, and TGA to confirm their formation. The SCXRD analysis revealed that TAPHIA 1 was crystallized in the Pca21 space group in an orthorhombic system while TAPHIA 2 was crystallized in the P21/c space group in a monoclinic system. The third-order NLO properties of both complexes were explored using the Z-Scan technique by employing a continuous wave (CW) diode laser of 520 nm. The third-order NLO parameters including nonlinear refractive index (n2), nonlinear absorption coefficient (β) and nonlinear optical susceptibility (χ (3)) were calculated at different powers; 40,50 and 60mW at fixed solution concentration (10mM) for both the complexes. Moreover, the experimental properties including NLO, FTIR, and UV were well corroborated with theoretical results obtained at the B3LYP-D3/6-31++G(d,p) level of theory. The analysis of the theoretical and experimental properties of both complexes suggests that TAPHIA 2 is a better applicant to be employed in optical devices than TAPHIA 1 due to the enhanced ability of internal charge transfer.

The influence of La/Mg co-doping on the structure, linear and nonlinear optical properties of Fe2O3 nanoparticles for environmentally friendly applications

The structure and linear/nonlinear optical properties of iron oxide (Fe2O3) nanoparticles (NPs) films are examined for environmentally friendly applications. Undoped and La, Mg and La/Mg co-doped Fe2O3 NPs films were equipped using the spray pyrolysis procedure. The structural, morphological and optical properties of the films were characterized by X-ray diffractometer, FT-IR spectrophotometer, FE-SEM and UV–visible–NIR spectrophotometer. XRD analysis exposes that the samples possess a rhombohedral structure of α- Fe2O3 (hematite). Besides, the crystallite size of the undoped Fe2O3 NPs increases from 20.7 nm to 21.8 nm (La/Fe2O3), 23.0 nm (Mg/Fe2O3) and 24.4 nm (La + Mg/Fe2O3). The direct/indirect optical band gap of the undoped Fe2O3 film decreases from 2.47 eV/1.87 eV to 2.43 eV/1.72 eV (La/Fe2O3), 2.37 eV/1.65 eV (Mg/Fe2O3) and 2.31 eV/1.56 eV (La + Mg/Fe2O3). Moreover, the effect of La/Mg co-doping on the refractive index, extinction coefficient, dielectric constants, linear optical susceptibility (χ(1)), third-order nonlinear susceptibility (χ(3)) and nonlinear refractive index (n2) of Fe2O3 NPs have been explored. In instance, the real dielectric constant of the undoped Fe2O3 NPs decreases at 600 nm from 6.46 to 5.00 (La/Fe2O3), 3.80 (Mg/Fe2O3) and 3.17 (La + Mg/Fe2O3). The ability to tailor the linear/nonlinear optical properties of Fe2O3 NPs films upon La/Mg co-doping nominate them for uses in a lot of environmentally friendly applications.

Measurement of nonlinear refractive indices of bulk and liquid crystals by nonlinear chirped interferometry.

The nonlinear refractive indices (n2) of a selection of bulk (LiB3O5, KTiOAsO4, MgO:LiNbO3, LiGaS2, ZnSe) and liquid (E7, MLC2132) crystals are measured at 1030 nm in the sub-picosecond regime (200 fs) by nonlinear chirped interferometry. The reported values provide key parameters for the design of near- to mid-infrared parametric sources, as well as all-optical delay lines.

Third-order nonlinear optical properties of choline chloride based deep eutectic solvents: Theoretical and experimental studies

In this work, the preparation of three deep eutectic solvents (DES) based on choline chloride as hydrogen bond acceptor and urea, malonic acid, and phenylpropionic acid as hydrogen bond donor is reported. These series of DES were used as models to measure, for the first time, the third-order optical nonlinearities in eutectic solvents. The nonlinear refractive index (n2) originated from the fast electronic response was determined by the close aperture Z-scan technique under excitation of laser ultrafast pulses at 800 nm, resulting in values of the order of ∼3 × 10-16 cm2 W−1, which are similar to those reported recently for ionic liquids. These values are also similar to those exhibited by some traditional polar protic organic solvents such as water and ethanol. At relatively low energy pulses, the DES presented only pure refractive response, but at high energies two of them exhibited nonlinear absorption. On the other hand, ab initio theoretical calculations using density functional theory (DFT) allowed to determine the static and dynamic second hyperpolarizabilities for the DES with M11/6-311G(d,p) level of theory. The tendency of the theoretical results agrees satisfactorily with the values of n2 obtained experimentally. Our results suggest that the presence of aromatic cloud makes that choline chloride:phenylpropionic acid contributes to produce relatively high n2 values. This study provides relevant information to be considered when DES are intended as an alternative to standard organic solvents in the development of photonic materials.

Optical and optoelectronic properties of (Ge2S8)100-xTex thin films for IR optical device fabrication

A detailed study of the optical and optoelectronic properties of (Ge2S8)100-xTex thin films for optical device fabrication is described in the present paper. Thin films of melt-quenched chalcogenide samples were deposited, on ultrasonically cleaned glass substrates, employing thermal evaporation technique. Transmission spectra were used to calculate the refractive index (n) and extinction coefficients (k). The refractive index increases from 2.187 to 2.329 by adding Te = 0 to 12. Dispersion parameters are evaluated using the WDD single oscillator model. The dielectric parameters real (εr) and imaginary (εi), electric modulus (M) and dielectric loss (tan δ) are used to evaluate the relaxation process in different compositions of (Ge2S8)100-xTex thin films. To further grasp the importance of amorphous chalcogenide compositions, we compute their optical conductivity (σ*op), electronic polarizability (αp), plasma frequency (ωp), metallization parameter (M), and refraction losses (RL) in optical devices. The dependency of Te content on the nonlinear refractive index (n2) and third-order susceptibility (χ(3)) is also calculated by an empirical formula, and it is found that the value of n2 increases from 11.938 × 10−12 to 20.615 × 10−12 esu, and the value of χ(3) rises from 6.8 × 10−13 to 12.472×10−13 esu with the addition of denser and higher atomic radius elements Te in the Ge-S system. The overall composition of Ge17.6S70.4Te12 is suitable as all-optical parameters show the maximum values that can be used for optical device purposes.

Push–pull octaphenylporphyrins with mixed substituents pattern: Synthesis, redox, ultrafast dynamics and nonlinear optical studies

A new family of β-functionalized octaphenylporphyrins, MOPP(NO2)Br3 (M = 2H, ZnII, NiII, or CuII, and OPP = octaphenylporphyrin) has been synthesized possessing unsymmetrical substitutions of bromo and nitro groups and the effect of asymmetrical substitutions on the redox, spectral, ultrafast dynamics, and nonlinear optical properties of the porphyrin macrocycles are investigated. Routes for the mixed functionalized OPPs begin with the bromination of NiOPP(NO2), leading to the formation of NiOPP(NO2)Br3 and H2OPPBr4. These ‘push–pull’ OPPs exhibited nonplanar conformation, red-shift in absorption spectra, tunable redox properties, and very high ground state dipole moments due to nonplanarity and asymmetric β-substitutions. All synthesized porphyrins exhibited a bathochromic shift (λmax = 23–38 nm) in the B band and λmax = 21–83 nm in the last Q band in comparison to MOPP due to attachment of the bromo and nitro groups on its peripheral positions. In the cyclic voltammograms, the first oxidation and reduction potential showed an anodic shift compared to its parent porphyrins due to the presence of strong electron acceptor bromo and nitro groups, which are present on the porphyrin periphery. These β-functionalized octaphenylporphyrins have shown excellent nonlinear optical response. The observed structure-dependent nonlinear refractive index (n2) values are in the range of ∼ 0.37–1.68 × 10−19 m2 W−1, and two-photon absorption coefficient (β) values are in the range of ∼ 0.19–4.56 × 10−12 m W−1. The transient absorption studies reveal that the decay dynamics of ZnOPP(NO2)Br3 exhibited long-lived τ1 component, while NiOPP(NO2)Br3 exhibited long-lived τ2 component than other OPP derivatives.

Exploring the impact of substrate placement on Cu3N thin films as a solar cell window layer: Structural and optical attributes

Copper nitride (Cu3N) thin films have garnered significant interest due to their exceptional stability, corrosion resistance, and optical qualities. In this research, Cu3N thin films were produced through reactive dc magnetron sputtering (dcMS) in a nitrogen/argon atmosphere on glass substrates without any external heat treatment. The study examined the effects of substrate positions from the cathode target, and subsequently film thicknesses, on the structure and optical properties of Cu3N thin films. Different methods were employed to examine the structural and optical characteristics of the films, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible-near infrared (UV–vis–NIR) spectrophotometry in the wavelength range of 400–2500 nm. The XRD patterns indicated a cubic crystal structure for the films with a dominant orientation along the (100) plane, while SEM images displayed uniform and smooth surface morphologies for the films. The UV–vis–NIR spectrophotometry findings demonstrated transmittance above 70% in the visible region for the films, and the optical bandgap values ranged between 2.29 and 2.49 eV. The optical conductivity (σ), electrical susceptibility (χc), and optical electronegativity (ηopt) have been calculated. Furthermore, the nonlinear optical qualities of Cu3N thin films were discussed, including the nonlinear refractive index (n2), the nonlinear optical susceptibility, and the nonlinear absorption coefficient (βc). The Cu3N thin films showed promising optical properties, suggesting their potential use as a window layer in solar cell technology.

Preparation and Optical Properties of PVDF-CaFe2O4 Polymer Nanocomposite Films.

In this work, a synthesis technique for highly homogeneous PVDF-CaFe2O4 polymer films direct from solution was developed. The structural characterizations were conducted using XRD, FTIR, and ESEM experimental techniques. The XRD characteristic peaks of CaFe2O4 nanoparticles revealed a polycrystalline structure. The average crystallite size for CaFe2O4 was calculated to be 17.0 nm. ESEM micrographs of PVDF nanocomposites containing 0.0, 0.25, 0.75, and 1.0 wt% of CaFe2O4 showed smooth surface topography. The direct Edir and indirect Eind band gap energies for the PVDF-CaFe2O4 nanocomposites were decreased with the additions of 0.0-1.0 wt% CaFe2O4. In addition, the refractive index (n0) increased from 3.38 to 10.36, and energy gaps (Eg) decreased from 5.50 to 4.95 eV. The nonlinear refractive index (n2) for the PVDF-CaFe2O4 nanocomposites was improved with the addition of CaFe2O4 nanoparticles, exceeding those reported in the literature for PVC, PVA, and PMMA nanocomposites. Therefore, the PVDF-CaFe2O4 nanocomposites are expected to take the lead in optoelectronic applications because of their unusual optical properties.

Evaluation of surface roughness, linear and nonlinear optical parameters of a mixture of sudan black b and polymer films for optical limiting application

A film of a mixture of sudan black b (SBB) dye and a poly methyl methacrylate (PMMA) is fabricated by casting. X-ray diffraction measurement proves the SBB/PMMA film's structure is amorphous. The scanning probe microscope confirmed that the SBB/PMMA film has a good quality and homogeneous surface. The SBB/PMMA film's optical constants are estimated via the transmittance, absorbance, and reflectance spectra. The indirect optical band gap is calculated and found to be 1.49 eV. The single oscillator energy, Eo, the dispersion energy, Ed, and the static refractive index, no, are computed by using Wemple and DiDomenico model. Semi-empirical relation, Z-scan, and diffraction ring patterns are three methods used to determine the film's nonlinear refractive index value. The SBB/PMMA film exhibited a high nonlinear refractive index (n2 = 7.83 × 10−7 cm2/W) and nonlinear absorption coefficient (β = 9.3 × 10−3 cm/W), calculated by the Z-scan method. Under a continuous wave laser beam, the property of the optical limiting of the film is examined. The film exhibited optical limiting properties with a limiting threshold value of 5 mW.

Diamondoid as potential nonlinear optical material by superalkali doping: A first principles study

Adamantane (C10H16), the smallest diamondoid molecule, has sparked considerable scientific interest due to its symmetric, single cage-shaped structure. In the current work, the geometric, electronic, and nonlinear optical responses of Li3O, Na3O and K3O clusters doped adamantanes have been investigated via DFT simulations. The calculated values of interaction energies (−5.50 to −6.91 kcal/mol) and vertical ionization energies (3.01–3.56 eV) reflected that the designed M3O-Ada complexes are thermodynamically and chemically stable. Charge transfer is probed through natural population analysis and the highest charge transfer (0.038 |e|) is observed for K3O-Ada complex. The electride nature of M3O-Ada complexes is confirmed through their electron density distribution and their energy gaps (2.19–3.06 eV) are reduced significantly. Interestingly, the absorption maxima (1387–1629 nm) of M3O-Ada electrides fall in the near infrared region. The highest first and second hyperpolarizability values of 5.9 × 105 au and 2.6 × 108 au are observed for K3O-Ada electride. The maximum hyper-Rayleigh scattering and second harmonic generation values of 1.3 × 107 au and 6.5 × 106 au are obtained at 1907 nm whereas the electro-optical Pockel's effect (6.5 × 106 au) is maximum at 1064 nm. Moreover, the dynamic second hyperpolarizability co-efficients (EOKE, EFISHG) are also computed at varying wavelengths. The M3O-Ada electrides exhibit the maximum nonlinear refractive index n2 of 1.9 × 10−7 cm2 W−1 at 1064 nm. This study will pave the way to the designing of stable superalkali doped diamondoids with enhanced NLO response.

Positron lifetime and third-order nonlinear optical studies of P(St-co-MMA)/NiO polymer nanocomposites

Polymer nanocomposites of Poly(styrene-co-methylmethacrylate) (P(St-co-MMA))/Nickel oxide (NiO) with different NiO nanoparticles wt% (0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) are prepared by solution casting technique. The UV–Vis and XRD results revealed decreased direct energy band gap, increased Urbach energy and decreased crystallinity with the increased NiO nanoparticles wt%. The SEM results show the agglomeration of nanoparticles for higher concentrations of NiO nanoparticles loading. The Z - scan studies show the increased nonlinear optical (NLO) parameters viz., nonlinear absorption coefficient (β), nonlinear refractive index (n2) and nonlinear susceptibility (χeff(3)) with increased NiO nanoparticles wt%. The free volume parameters viz., free volume (Vf) and fractional free volume (Fv) show increasing and decreasing trends with the NiO nanoparticles concentration respectively. The effect of free volume parameters on nonlinear optical parameters such as β,n2 and χeff(3) is brought out. The increased β,n2 and χeff(3) is due to the increased polarization by the NiO nanoparticles in P(St-co-MMA) polymer matrix. The decreased fractional free volume (Fv) with the increased NiO (wt%) indicates the increased packing density of polymeric chains of P(St-co-MMA) polymer matrix. The increased NLO parameters are attributed to the increased polarizability and packing density of polarizable groups in the P(St-co-MMA) polymer matrix.

Comparative studies of the structural and optical properties of BiI3 and PbI2 iodide-based semiconductors

ABSTRACT The structural and optical properties of BiI3 and PbI2 powders were compared. The x-ray diffraction results confirm that PbI2 crystallizes in a hexagonal structure, while BiI3 in a rhombohedral structure. The optical band gap Eg was found to be direct at (2.31 eV) for PbI2 and indirect (1.7 eV) for BiI3. Different fundamental optical properties such as refractive index, real and imaginary parts of optical conductivities, dielectric function, and linear susceptibility were determined. The non-linear optical properties were also discussed by deriving the linear and non-linear susceptibilities using Wemple–DiDomenico single-oscillator model. The third-order susceptibility at low absorption region was found to be equal 2.684×10−15 [esu] and 3.685×10−15 [esu], as well as the non-linear refractive index n2, 7.5×10−14 [esu] and 1.07×10−13 [esu] for BiI3 and PbI2 respectively, which evidences their interest in optoelectronic devices.