Third-order nonlinear optical response of newly synthesized accepter/donor substituted propylidene aryloxy acet hydrazide

A class of organic compounds namely propylidene aryloxy acet hydrazide derivatives were synthesized. The third-order nonlinear optical properties and optical limiting studies of the compounds were investigated using the single beam Z-scan technique at 532 nm. The Z-scan study reveals that the compounds exhibit a self-defocusing effect at 532 nm. The calculated values of nonlinear refractive index, third-order nonlinear optical susceptibility and second order molecular hyperpolarizability are of the order of 10^?11 esu, 10^?13 esu and 10^?31 esu, respectively. The compounds exhibit good optical limiting properties at the wavelength used.     

Third order nonlinear optical properties of ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate (III)

A novel organometallic compound, ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate (III), abbreviated as TPEPADT, was synthesized. The TPEPADT doped poly(methyl methacrylate) (PMMA) thin film with a mass fraction of 1% (1 wt.%) was prepared by using a spin-coating method. The third-order nonlinear optical properties of TPEPADT in acetonitrile solution and TPEPADT-doped PMMA thin film were investigated by using the laser Z-scan technique at the wavelength 1064 nm with laser duration of 20 ps. The linear refractive index of the polymer thin film was also studied. The Z-scan curves revealed that both TPEPADT in acetonitrile solution and the polymer thin film possessed negative nonlinear refraction, exhibiting a self-defocusing effect and nonlinear absorption was negligible under the experimental conditions used. The nonlinear refractive index was calculated to be ?1.9 × 10^?18 m²/W for TPEPADT in acetonitrile solution and ?8.9 × 10^?15 m²/W for the polymer thin film. These results suggest that TPEPADT have potential for the application of all-optical switching devices.     

Nonlinear optical features of δ-BiB3O6/PVA polymer nanocomposites deposited on aluminum-doped zinc oxide substrates containing Ag nanoparticles

For the first time the Z-scan measurements and second harmonic generation of δ-BiB₃O₆:Pr³⁺ large-size nanocrystallites embedded into the polyvinyl alcohol (PVA) polymer matrices and deposited on AlZnO substrates decorated with Ag NP were studied. The comparison of the second and third order NLO is presented. The Z-scan measurements were done by 5 ns Nd:YAG laser and the second harmonic generation was measured using the 25 ns Nd:YAG laser with frequency repetition about 10 Hz. The measurements have shown that both second as well as third-order susceptibilities are sensitive to the sizes of the Ag NP deposited on the AlZnO substrate. The obtained results confirm a principal role of the Ag NP on the output nonlinear optical properties which may be a consequence of the contribution of the low-dimensional nano-trapping levels.     

Structural,optical, thermal and mechanical characterization of an organic nonlinear optical material: 4-methyl-3-nitrobenzoic acid single crystal

Organic single crystals of 4-methyl-3-nitrobenzoic acid (4M3N) have been grown by slow evaporation solution growth technique at room temperature. The single crystal X-ray diffraction study reveals that 4M3N crystallizes in monoclinic system with space group P21/n. The crystalline perfection of the crystal was analyzed by high resolution X-ray diffraction (HRXRD) measurements. The functional groups present in 4M3N have been identified from FT-IR and FT-Raman spectra. The lower cut-off wavelength of 4M3N is found to be 404 nm and the optical band gap is calculated as 2.91 eV. The refractive index shows normal behavior with wavelength. The physio chemical changes, decomposition and stability of the 4M3N compound were established by TG-DTA studies. Vickers microhardness measurement concludes that 4M3N belongs to soft material (n=2.5) category. The LDT value is found to be higher than that of KDP and some of the important organic NLO materials. The third order nonlinear refractive index and nonlinear absorption coefficient of the 4M3N have been measured by Z-scan studies. The imaginary and real parts of the third-order susceptibility values were determined as Im χ³=9.129×10⁻¹¹ esu and Re χ³=1.4034×10⁻⁹ esu respectively. The dislocation density was calculated to be 3.0448×10⁶ cm⁻² which indicates the quality of the crystal.     

Defects related emission and nanosecond optical power limiting in CuS quantum dots

We report optical and nonlinear optical properties of CuS quantum dots and nanoparticles prepared through a nontoxic, green, one-pot synthesis method. The presence of surface states and defects in the quantum dots are evident from the luminescent behavior and enhanced nonlinear optical properties measured using the open aperture Z-scan, employing 5 ns laser pulses at 532 nm. The quantum dots exhibit large effective third order nonlinear optical coefficients with a relatively lower optical limiting threshold of 2.3 J cm⁻², and the optical nonlinearity arises largely from absorption saturation and excited state absorption. Results suggest that these materials are potential candidates for designing efficient optical limiters with applications in laser safety devices.     

Third-order optical nonlinearities of an organometallic complex: Bis(tetra-n-propylammonium)bis(2-thioxo-1,3-dithiole-4,5-dithiolato)cuprate(II) doped in solid PMMA films

An organometallic complex, bis(tetra-n-propylammonium)bis(2-thioxo-1,3-dithiole-4,5-dithiolato)cuprate(II), [(C₃H₇)₄N]₂[Cu(dmit)₂] (dmit^2?=4,5-dithiolate-1,3-dithiole-2-thione), abbreviated as PrCu, was synthesized. The films of PrCu were prepared using spin coating method. The third-order nonlinear optical properties of PrCu in acetone solution and PMMA films were investigated by Z-scan technique at 1064 nm with laser duration of 20 ps. The Z-scan spectra reveal that the composite films exhibit large negative nonlinear refractive indices of the order of 10^?15 m²/W, which are three orders larger than that in acetone solution. The nonlinear absorption coefficients were calculated to be 9.416×10^?10 m/W. For the composite films, the figure of merit, W and T, meet the requirement of all-optical switching devices. The experimental results show that the PrCu-doped PMMA films have potential applications for nonlinear optical devices.     

The study on the nonlinear optical response of Sudan I

The nonlinear optical properties of Sudan I were investigated by a single beam Z-scan technique. The Sudan I ethanol solution exhibited large nonlinear refractive indices under both CW and pulse laser excitations. The nonlinear refractive indices of Sudan I were in the order of ?10^?8 cm²/W under CW 633 nm excitation and ?10^?6 cm²/W under CW 488 nm excitation, respectively. Under the excitation of a pulse 532 nm laser, the nonlinear refractive index n₂ was calculated to be 1.19 × 10^?14 cm²/W. It was discussed that the mechanism accounting for the process of nonlinear refraction was attributed to the laser heating for the CW laser excitation and the electronic effect for the pulse excitation. Moreover, the second hyperpolarizability of Sudan I was also estimated in this paper.     

Influence of thickness and annealing on linear and nonlinear optical properties of manganese (III) chloride tetraphenyl porphine (MnTPPCl) organic thin films

Thin films of manganese (III) chloride 5,10,15,20-tetraphenyl-21H,23H-porphine (MnTPPCl) with different film thickness were deposited by an evaporation technique. Some optical constants were calculated for these films at a thickness of 110, 220 and 330 nm and annealing temperature of 373 and 437 K. IR spectrum demonstrating that the thermal evaporation method is a good one to acquire undissociated and stoichiometric MnTPPCl films. Our perceptions demonstrate that the mechanism of the optical absorption obeys with the indirect transition. It was found that the energy gap, E_g, affected by the film thickness and annealing. Dispersion of the refractive index is described using single oscillator model. Dispersion parameters are calculated as a function of the film thickness and annealing temperature. In addition, the third-order nonlinear susceptibility, χ⁽³⁾, and the nonlinear refractive index, n₂, were calculated.     

Non-linear optical properties and all optical switching of Congo red in solution

We present the results from investigations of the nonlinear properties of Congo red solutions using Z-scan technique with a continuous wave argon ion laser at 514 nm. The magnitude and sign of the third-order nonlinear refractive index n₂ of aqueous solution of Congo red were determined. The nonlinear refractive index was found to vary with concentration. Third-order nonlinearity is dominated by nonlinear refractive index, which leads to strong self-defocusing and self diffraction in the samples studied. A pump and probe technique was used to investigate the origin of nonlinearity. Furthermore the nonlinear refractive index effect was utilized to demonstrate all optical switching. The optical limiting behavior based on nonlinear refractive index was investigated.     

Nonlinear optical properties of silver colloidal solution by in situ synthesis technique

The silver colloidal solutions were prepared by in situ synthesis technique in the presence of the Polymethyl Methacrylate, which was polymerized by reversible addition-fragmentation transfer. The UV–VIS spectra and transmission electron microscopy had shown the formation of sphere silver nanoparticles with average size of 10 nm. Nonlinear optical properties as a function of silver concentration were studied using Z-scan technique with 13 ns pulse duration at 532 nm. The optical nonlinearity enhancement was observed by increasing the concentration. The third-order nonlinear susceptibility χ⁽³⁾ was measured to 1.045 × 10⁻¹¹ esu when the concentration was 2.13 mg/ml. Besides, the sample was founded to exhibit a shift from saturable absorption to reverse saturable absorption at higher incident laser energy. The reverse saturable absorption was observed to be responsible for the optical limiting characteristics in our experiments.     

Titanium oxide thin layers deposed by dip-coating method: Their optical and structural properties

TiO₂ thin films were prepared by sol-gel method. The structural investigations performed by means of X-ray diffraction (XRD) technique and scanning electron microscopy (SEM) showed the shape structure at T = 600 °C. The optical constants of the deposited film were obtained from the analysis of the experimentally recorded transmittance spectral data in the wavelength of 200–3000 nm range. The values of some important parameters of the studied films are determined, such as refractive index n and thickness d. In this work, using the transmission spectra, we have calculated the dielectric constant (ε_∞) for four layered TiO₂ films; a simple relation is suggested to estimate the third-order optical nonlinear susceptibility χ⁽³⁾. It has been found that the dispersion data obeyed the single oscillator of the Wemple–DiDomenico model, from which the dispersion parameters and high-frequency dielectric constant were determined. The estimations of the corresponding band gap E_g, χ⁽³⁾ and ε_∞ are 2.57 eV, 0.021 · 10⁻¹⁰ esu and 5.20, respectively.     

Characterization and nonlinear optical properties of PVP/TiO2 nano-fibers doping with Ag colloid nano-particles

We synthesized PVP/TiO₂ nano-fibers doping with Ag colloid nano-particles by electro-spinning method. These nano-fibers were characterized by UV/visible/NIR spectroscopy, SEM and XRD. The image of SEM showed that the synthesized nano-fibers were monotonous and without knot and had a diameter about 150 nm. We also measured the nonlinear refractive and absorption indexes of the sample in three different intensities using the single beam Z-scan method by a continuous wave (CW) He–Ne laser at 632.8 nm wavelength. The nonlinear refraction indexes of these nano-fibers were measured in order of 10⁻⁷ (cm²/W) with negative sign and the nonlinear absorption coefficient was obtained in order of 10⁻³ (cm/W).     

Nonlinear optical properties of erbium doped zinc oxide (EZO) thin films

Undoped and Erbium (Er) doped zinc oxide (EZO) thin films were deposited on glass substrate by sol–gel method using spin coating technique with different doping concentration. EZO films were characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV–VIS-NIR transmission and single beam z scan method under illumination of frequency doubled Nd:YAG laser. The deposited films were found to be well crystallized with hexagonal wurtzite structure having a preferential growth orientation along the ZnO (002) plane. A blue-shift was observed in the band gap of EZO films with increasing Er concentration. All the films exhibited a negative value of nonlinear refractive index (n₂) at 532 nm which is attributed to the two photon absorption and weak free carrier absorption. Third order nonlinear optical susceptibility, χ⁽³⁾ values of EZO films were observed in the remarkable range of 10^? 6 esu. EZO (0.4 at.%) sample was found to be the best optical limiter with limiting threshold of 1.95 KJ/cm².     

Diffraction patterns and nonlinear optical properties of gold nanoparticles

Stable gold nanoparticles have been prepared by using soluble starch as both the reducing and stabilizing agents; this reaction was carried out at 40 °C for 5 h. The obtained gold nanoparticles were characterized by UV–Vis absorption spectroscopy, transmission electron microscopy (TEM) and z-scan technique. The size of these nanoparticles was found to be in the range of 12–22 nm as analyzed using transmission electron micrographs. The optical properties of gold nanoparticles have been measured showing the surface plasmon resonance. The second-order nonlinear optical (NLO) properties were investigated by using a continuous-wave (CW) He–Ne laser beam with a wavelength of 632.8 nm at three different incident intensities by means of single beam techniques. The nonlinear refractive indices of gold nanoparticles were obtained from close aperture z-scan in order of 10^?7 cm²/W. Then, they were compared with diffraction patterns observed in far-field. The nonlinear absorption of these nanoparticles was obtained from open aperture z-scan technique. The values of nonlinear absorption coefficient are obtained in order of 10^?1 cm/W.     

Investigation of third-order nonlinear optical properties of NNDC-doped PMMA thin films by Z-scan technique

A novel chalcone derivative, (2E)-1-(2,4-di- chloro-5-fluorophenyl)-3-[4-dimethylamino)phenyl]prop-2-en-1-one, abbreviated as NNDC, was prepared and characterized by elemental analyses, infrared (IR) and proton nuclear magnetic resonance (¹H NMR) spectrum, and thermal analyses. The NNDC-doped poly(methyl methacrylate) (PMMA) thin films with five different doping concentrations by weight were prepared by using a spin-coating method. Their linear optical properties were investigated by using a prism coupling measuring system. The third-order nonlinear optical properties of NNDC in 1,2-dichloroethane (NNDC/1,2-dichloroethane) solution and NNDC-doped PMMA (NNDC/PMMA) films were investigated by using the laser Z-scan technique with 20 ps pulses at 532 nm. A self-focusing effect was observed from the Z-scan curves for solution and thin films and the nonlinear refractive index of the film increases with the increase of the doping concentration. In addition, nonlinear absorption was negligible for all samples. The magnitude of third-order nonlinear refraction index n ₂ and the third-order nonlinear susceptibility χ ⁽³⁾ for thin films were 10⁻¹⁵ m²/W and 10⁻⁹ esu, respectively, which are about three orders larger than that of NNDC/1,2-dichloroethane solution. Some necessary analyses were presented. The results show that this material is a promising candidate for application in the nonlinear optical devices at 532 nm.     

Studies on third-order nonlinear optical properties and reverse saturable absorption in polythiophene/poly (methylmethacrylate) composites

We report here the studies on third-order nonlinear optical properties of two novel polythiophene composite films investigated using the Z-scan technique. The measurements were carried out using a Q-switched, frequency doubled Nd:YAG laser producing 7 nanosecond laser pulses at 532 nm. Z-scan results reveal that the composite films exhibit self-defocusing nonlinearity. The real and imaginary parts of the third-order nonlinear optical susceptibility were of the order 10⁻¹² esu. The effective excited-state absorption cross section was found to be larger than the ground state absorption cross section, indicating that the operating nonlinear mechanism is reverse saturable absorption (RSA). The polythiophene composite films also exhibit good optical power limiting of the nanosecond laser pulses. The nonlinear optical parameters are found to increase on increasing the strength of the electron-donor group, indicating the dependence of χ ⁽³⁾ on the electron-donor/acceptor units of polythiophenes.     

Structural,optical and dispersion characteristics of nanocrystalline GaN films prepared by MOVPE

In this work, nanocrystalline GaN film was grown on a c-plane sapphire substrate by metal-organic vapor phase epitaxy (MOVPE). The structural and optical properties of the nanocrystalline GaN thin film were studied. The morphological and structural properties of GaN film were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. According to the X-ray diffraction spectrum, a GaN film was formed with a wurtzite structure, which is the stable phase. The optical parameters were determined using spectrophotometric measurements of transmittance and reflectance in the wavelength range 200–2500 nm. The analysis of the spectral behavior of the absorption coefficient in the intrinsic absorption region reveals a direct allowed transition with a band gap of 3.34 eV. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple–Didomenico (WD) model. The single oscillator energy (E_o), the dispersion energy (E_d), the high frequency dielectric constant (ε_∞), the lattice dielectric constant (ε_L) and the free charge carrier concentration (N) were estimated. From the optical dielectric analysis, the optical conductivity, volume and surface energy loss functions were calculated. Moreover, the third-order nonlinear optical susceptibility χ⁽³⁾ was also considered.     

Synthesis and growth of sodium bitartrate monohydrate a new organometallic nonlinear optical single crystal

Sodium bitartrate monohydrate (SBTMH) a new organometallic nonlinear optical material, with molecular formula, [C₄H₅NaO₆ · H₂O] has been synthesized at ambient temperature. Spectral, thermal and optical techniques have been employed to characterize the new material. Bulk single crystals of size 13 × 4 × 4 mm³ of SBTMH have been grown by slow cooling method. The unit cell parameters of the grown crystal were determined by single crystal XRD. Functional groups present in the sample were identified by FTIR spectral analysis. Thermal stability of SBTMH was determined using TGA/DTA. The grown crystals exhibit nonlinear properties. The dielectric response of the crystal with varying frequencies was studied. The optical transparency range and the lower cut-off wavelength of the material were identified from the UV–vis–NIR absorption spectrum.     

The annealing effect on structural,optical and photoelectrical properties of CuInS2/In2S3 films

Successive Ionic Layer Adsorption and Reaction (SILAR) technique was used to deposit the CuInS₂/In₂S₃ multilayer thin film structure at room temperature. The as-deposited film was annealed at 100, 200, 300, 400 and 500 °C for 30 min in nitrogen atmosphere and the annealing effect on structural, optical and photoelectrical properties of the film was investigated. X-ray diffraction (XRD) and optical absorption spectroscopy were used for structural and optical studies. Current–Voltage (I–V) measurements were performed in dark environment and under 15, 30 and 50 mW/cm² light intensity to investigate the photosensitivity of the structure. Also, the electrical resistivity of the film was determined in the temperature range of 300–470 K. It was found that annealing temperature drastically affects the structural, optical and photoelectrical properties of the CuInS₂/In₂S₃ films.     

Nonlinear optical properties of CdxZn1 − xO films deposited with PLD technique

In this paper, the structural and optical properties of Cd_xZn_1 ? xO films were studied. The films were deposited with pulse laser deposition (PLD) technique. The Cd concentration changed in the range from x = 0 to 0.2. The structure of the films was characterized by atom force microscope (AFM) and X-ray diffraction (XRD). The nonlinear optical properties were investigated by Z-scan methods. The two-photon absorption (TPA) coefficient β_eff was measured. The β_eff value changes from 49.2 cm/GW to 116.5 cm/GW with the Cd concentration from 0 to 15%.