Values Of Nonlinear Absorption Coefficient Research Articles

Zinc oxide encapsulated poly (vinyl alcohol) nanocomposite films as an efficient third-order nonlinear optical material: Structure, microstructure, emission and intense low threshold optical limiting properties

Keeping in view the significant facts on Zinc Oxide (ZnO) and Poly (Vinyl Alcohol) (PVA), we developed nanocomposite films comprising small weight percentage of ZnO content in host polymer PVA, choosing a simple and cost-effective method based on solution-casting. The investigations of its structure, microstructure, linear/luminescence and nonlinear optical properties are presented. This article mainly discusses the intense low threshold nonlinear absorption (NLA) behaviour displayed by the samples, as studied using the standard Z-scan technique. On either increasing the intensity or ZnO content, the samples exhibited a switchover from saturable to reverse saturable absorption, which is rarely observed under 442 nm continuous wave (CW) laser light excitation. The effective values of nonlinear absorption coefficient and imaginary part of third-order nonlinear susceptibility are higher than the recently reported results. The limiting threshold values (obtained from optical limiting curves) are also found to be much better than other reported ones.

Ablated nickel nanoparticles: third harmonic generation and optical nonlinearities

We report the two-photon absorption and nonlinear refraction studies of the nickel nanoparticles (NPs) in deionized water using femtosecond laser pulses at 400 and 800 nm. The laser ablation technique was employed for the synthesis of nickel NPs using nanosecond, picosecond, and femtosecond pulses. The largest values of nonlinear absorption coefficients and nonlinear refractive indices were determined to be 9 × 10−11 cm W−1 and 2 × 10−15 cm2 W−1 for smaller sized nickel NPs suspension. Third harmonic generation from the Ni plasma which contained NPs was analyzed using picosecond and femtosecond pulses as heating radiation and femtosecond probe pulses.

Fluorescent meso-benzyl curcuminoid boron complex: Synthesis, photophysics, DFT and NLO study

Curcumin based fluorescent NLOphore was synthesized. Solvent polarizability (SP) was found to be responsible for the solvatochromic nature of dye as confirmed from the multilinear regression analysis. DFT computations using global hybrid (B3LYP and BHHLYP) and range-separated hybrid (CAM-B3LYP) functionals with the basis set 6-31 + G(d,p) were performed to determine the linear as well as NLO properties. NLO response was measured using Z scan technique. The computed NLO values (βo = 426.64 × 10−30 esu) were found to be superior to that of urea (βo = 0.371 × 10−30 esu). The value of nonlinear absorption coefficient (β) and third-order nonlinear susceptibility (χ)3 were found to be 2.19 × 10−12 (m/W) and is 2.09 × 10−13 (e.s.u) respectively. The result of present work might be useful for the designing of curcumin based NLOphores for industrial applications.

Structural, third-order optical nonlinearities and figures of merit of (E)-1-(3-substituted phenyl)-3-(4-fluorophenyl) prop-2-en-1-one under CW regime: New chalcone derivatives for optical limiting applications

In the present work, the crystal structures and third-order nonlinear optical (NLO) properties of two novel chalcone derivatives, (E)-1-(3-bromophenyl)-3-(4-fluorophenyl) prop-2-en-1-one (F3BC) and (E)-1-(3-nitrophenyl)-3-(4-fluorophenyl) prop-2-en-1-one (F3NC) have been experimentally investigated. Both chalcones were synthesized by Claisen–Schmidt condensation reaction. The single-crystals were obtained from slow evaporation solution growth method and were structurally characterized by single-crystal X-ray diffraction. Both studied crystals are crystallized in centrosymmetric space groups. The existence of CH⋯π interactions in F3BC and CH⋯O and CH⋯F hydrogen interactions in F3NC play important roles in creating supramolecular structures. The linear optical absorption coefficient (α) of F3BC and F3NC were analyzed by UV–Vis–NIR spectral analysis and the optical band gaps (Eg) were estimated. TG-DTA analysis revealed that the F3NC crystal has higher thermal stability than F3BC crystal. The third-order nonlinear optical properties of these crystals were studied in solution using Z-scan technique with a continuous wave (CW) DPSS laser operating at 532 nm wavelength. The molecules reveal a strong third-order nonlinear absorption (NLA) and negative nonlinear refraction (NLR). The calculated values of nonlinear absorption coefficient β, nonlinear refraction coefficient n2 and third-order nonlinear susceptibility χ(3) were found to be of the order of 10−5 cm/W, 10−8 cm2/W and 10−6 esu, respectively. The value of the two-photon absorption (2 PA) cross section at 532 nm for both chalcones is of the order of 108 GM. These crystals also exhibited optical limiting (OL) properties under CW laser excitation.

A study on the linear and nonlinear optical properties of Li and NH4 doped potassium pentaborate crystals

In this letter, we report on the linear and nonlinear optical investigations of 5mol% of Li, NH4 doped potassium pentaborate (KB5) crystal. Doping concentration was quantified by the EDAX and ICP analysis. The enhancement of transparency in the doped crystals was recorded in UV–vis–NIR spectra. Optical band gap of the pure and doped crystals was also calculated. The optical nonlinearity of the grown crystals was confirmed by Second Harmonic Generation (SHG) test which shows that the dopants in the KB5 crystal enhanced the SHG efficiency of that material. The third order nonlinearity was studied by Z- scan technique using 632.8nm He-Ne laser. The values of nonlinear absorption coefficient (β) and nonlinear refractive index (n2) were calculated. Third order nonlinear susceptibility (χ(3)) of the Li and NH4 doped crystals is 1.0278×10−3esu and 0.7744×10−3esu respectively which is higher than that of pure KB5 (0.6770×10−3esu).

Influence of Pr Doping on the Structural, Morphological, Optical, Luminescent and Non-linear Optical Properties of RF-Sputtered ZnO Films

The effects of Pr doping on the structural, morphological, optical and non-linear optical properties have been investigated. X-ray diffraction and Raman analysis reveals the formation of highly c-axis-oriented films with hexagonal wurtzite structure of ZnO. Atomic force microscopy and scanning electron microscopy images reveal the formation of grains with well-defined grain boundaries. The Pr-doped films present excellent optical transparency in the visible region. The photoluminescence spectra show both UV and visible emissions and the intensity of the visible emission increases with Pr doping. Nonlinear optical properties of the Pr-incorporated ZnO nanostructures have been investigated using the open aperture Z-scan technique. It is interesting to note that 1 wt.% praseodymium-incorporated ZnO film shows saturable absorption, whereas the 5 wt.% praseodymium-incorporated ZnO shows reverse saturable absorption and the high value of non-linear absorption coefficient (β) for 5 wt.% Pr-doped ZnO film suggests the suitability of these films for optoelectronic device applications.

Investigation of non-linear optical properties of CdS/PS polymer nanocomposite synthesized by chemical route

Cadmium Sulfide (CdS) nanoparticles play an important role in non-linear optoelectronic devices. CdS/Polystyrene(PS) nanocomposite has been prepared by chemical ex-situ route and characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet–visible (UV–vis) and Photoluminescence (PL) spectroscopy. XRD spectra of CdS/PS nanocomposite reveals the cubic phase of CdS nanoparticles with average crystallite size ~2.54nm. The vibrational band corresponding to Cd–S bond has been observed at 406.57cm−1 in FTIR spectra of CdS/PS nanocomposite along the typical styrene bonds. Quantum confinement effect in the CdS/PS nanocomposite has been confirmed from the UV–vis spectra. In PL emission spectra, in addition to band to band transition emission, the green and yellow bands have been observed due to the interstitial sulfur and cadmium defect states respectively. Z-scan technique has been utilized to study the non-linear optical properties of the CdS/PS nanocomposite. The value of non-linear absorption coefficient (β) and non-linear refractive index (n2) has been calculated. The large value of third order non-linear susceptibility is due to the quantum confinement effect plus the thermal lensing effect produced across the sample.

Specific features of resonant nonlinear absorption in colloidal solutions of CdSe/ZnS quantum dots

Nonlinear refraction coefficients and nonlinear absorption coefficients of colloidal solutions of CdSe/ZnS quantum dots (QDs) have been measured by the z-scan method. Resonant excitation was carried out by a Nd:YAG laser (λ = 532 nm, τ ∼ 7 ns). QDs have been chosen to correspond to different positions of the peak of the fundamental exciton absorption band with respect to the laser wavelength. The z-scan data are compared with the optical-limitation photodynamics data on CdSe/ZnS QD solutions. The obtained values of nonlinear absorption coefficients and their dependence on the QD size are interpreted in terms of the two-step mechanism of optical limitation.

Investigation of optical nonlinearity and diffraction ring patterns of carbon nanotubes

Abstract The third order nonlinear optical properties of multi-wall carbon nanotubes (MWNT), single-wall carbon nanotubes (SWNT) dissolved in 1,2-dichlorobenzene and SWNT doped poly(ethylacetylenecarboxylate) polymer have been studied using Z-scan technique. Experiments are performed using a CW diode laser at 635 nm wavelength with 26 mW power. It has been found that the values of nonlinear absorption coefficient β, nonlinear refractive index n2, Re χ3, and Im χ3 in SWNT are larger than in MWNT. It was noticed that the closed-aperture Z-scan is most effective when the linear transmittance of the aperture “S” is small. Laser-induced diffraction ring patterns were observed only for SWNT. Based on the number of diffraction rings, variation of refractive index Δn and the relative phase shift ∆ϕ(r) have been estimated at different input laser power: 5, 10, 15 and 25 mW.

Study of self-defocusing, reverse saturable absorption and photoluminescence in anthraquinone PMMA nanocomposite film

The nanocomposite film of 1,5-diamino-9,10-anthraquinone in poly methyl methacrylate has been fabricated by following guest–host method. Intense reverse saturable absorption and self-defocusing effect have been investigated by employing Z-scan technique with low power CW laser at 532nm with different intensities for the dye-polymer composite film. The estimated values of nonlinear absorption coefficient β, nonlinear refractive index n2 and third order susceptibility χ(3) of the composite film are of the order of 10−3 (m/W), 10−11 (m2/W) and 10−4 (esu), respectively. The dye molecules have been encapsulated uniformly between molecules of polymer as a nanocomposite with average roughness ∼7.96nm as characterized by AFM technique. The nanocomposite film also exhibited strong photoluminescence emission when excited with 532nm. The second order hyperpolarizability of composite film has also been estimated. The evaluated figure of merit W having a value greater than 1, and the results obtained suggest that the composite film of 1,5-diamino-9,10-anthraquinone-PMMA has potential applications in nonlinear optical devices.

Nonlinear optical behavior of metal octaphenoxy phthalocyanines: effect of distortion caused by the central metal

In this work, we investigated the nonlinear optical absorption properties of chloroaluminum, chlorogallium, chloroindium, zinc and lead octaphenoxy phthalocyanines in a dimethyl sulphoxide solution using 5 ns pulses at 532 nm. Using the Z-scan technique, the nonlinear optical properties and the excited state absorption cross-sections were determined by fitting the Z-scan data. The k value was the highest for Pb derivative at 211, making it the best nonlinear optical material. In terms of hyperpolarizability, Pb derivative (containing a larger central metal) also gave the largest value followed by aluminum derivative (containing a small central metal). The distortion of the ring caused by the central metal is used to explain the hyperpolarizability values. Large nonlinear absorption coefficient values, β eff , in the range of 3.558–4.763 × 10-9 cm.W-1 and low saturation fluence values, F sat between 21.5–38.5 mJ.cm-2, were obtained for these samples.

Synthesis and study of optical properties of linear and hyperbranched conjugated polymers containing thiophene and triphenylamine units

We report the synthesis of solution processable donor–acceptor type conjugated monomer (M1) and polymers (P1 and P2) consisting of electron-accepting 1,3,4-oxadiazole unit and electron-donating 3,4-didecyloxythiophene, and triphenylamine units through Wittig polycondensation reaction. The linear polymer P1 is thermally stable up to 325 °C whereas the hyperbranched polymer P2 showed better thermal stability with an onset of decomposition at 375 °C. Polymer P2 showed lower band gap energy (1.96 eV) than that of P1 (2.09 eV). Polymers P1 and P2 emit yellow and orange light, respectively, under the irradiation of UV light. Electrochemical studies revealed that the polymers possess high-lying highest occupied molecular orbital and low-lying lowest unoccupied molecular orbital energy levels. Polymer light-emitting diodes are fabricated with the device configuration of ITO/PEDOT:PSS/polymer (P1 or P2)/Al. The device based on P2 showed a very low threshold voltage of 2 V. The third-order nonlinear optical properties of the polymers are studied using Z-scan technique. Both polymers showed a strong optical limiting behavior. The value of nonlinear absorption coefficient (β) of the polymers is of the order 10−10 mW−1 which indicates that these materials may be accomplished for fabricating optical limiters.

Diode laser frequency doubling in a ppMgO:LN ridge waveguide: influence of structural imperfection, optical absorption and heat generation

In this work, we investigate experimentally and theoretically limitations of highly efficient high-power single-pass second-harmonic generation process in a quasi-phase matched magnesium oxide-doped lithium niobate ridge waveguide due to structural imperfections, optical absorption and resulting heat generation. With the distributed Bragg reflector diode laser emitting at 1,061 nm, applied in the presented bench-top experiment, a coupling efficiency into the ridge waveguide nonlinear device of 86 % is realized. An internal normalized conversion efficiency of 375 % (Wcm $${}^2$$ ) $${}^{-1}$$ is determined. A maximum second-harmonic power of 386 mW is reached at a corresponding opto-optical and electro-optical conversion efficiency of 38 and 9.5 %, respectively. A saturation of the conversion efficiency at a high power level as well as its dependency on the nonlinear device structure inhomogeneity are confirmed experimentally. With a theoretical model incorporating geometrical inhomogeneity, linear and nonlinear absorption and resulting heat load the second-harmonic generation in a ridge waveguide can be simulated realistically. Increased values of nonlinear absorption coefficients, higher than until now reported, lead to a very good agreement between theoretical and experimental results. Moreover, according to the simulation, structural inhomogeneities can enhance the SHG conversion efficiency at high output powers.

Large Nonlinear Optical Absorption Response in Monolayer Graphene and Graphene Oxide

Nonlinear absorption of monolayer graphene and graphene oxide suspensions were studied in the wavelength of 800 nm by Z-scan method with 50fs pulses. Large reverse saturable absorption is observed in graphene, while graphene oxide shows saturable absorption at the incident intensity of 46 GW/cm2. The values of nonlinear absorption coefficient also have been determined from the experimental data. The NLA coefficient β of the monolayer graphene suspension is 1.96×10-2cm/GW,while the NLA coeffiecient β of graphene oxide is-6.84×10-3cm/GW.

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 cm 2/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.

Synthesis and third order optical nonlinearity studies of the donor–acceptor conjugated polymer, poly(2-[3,4-didodecyloxy-5-(1,3,4-oxadiazol-2-yl)thiophen-2-yl]-5-phenyl-1,3,4-oxadiazole) and a polymer/TiO 2 nanocomposite

A donor–acceptor conjugated polymer (PDOThPOD) containing 3,4-didodecyloxythiophene and (1,3,4-oxadiazolyl)benzene units is synthesized by using precursor polyhydrazide route. Cyclic voltammetry studies reveal that the polymer possesses a low-lying LUMO energy level (−3.57 eV). A nanocomposite of polymer PDOThPOD and nano TiO 2 is also prepared. The linear optical properties of PDOThPOD and the nanocomposite are studied using UV–vis absorption spectroscopy and fluorescence emission spectroscopy. z-scan technique is used to study the third order nonlinear optical properties of the polymer and nanocomposite films. Both polymer and nanocomposite films show a strong optical limiting behavior. The value of nonlinear absorption coefficient ( β) is found to be of the order of 10 −7 m/W, indicating that these materials are potentially suited for fabricating optical limiters.

Tailoring surface plasmon resonance in Ag:ZrO 2 nanocomposite thin films

Ag:ZrO 2 nanocomposite thin films have been synthesized by a modified sol–gel technique. The effect of post-deposition treatments i.e. thermal annealing and UV irradiation on micro-structural, chemical and optical properties of nanocomposite thin films have been studied by a transmission electron microscope, X-ray photoelectron spectrophotometer and UV–vis spectrophotometer. Films deposited with a polymeric ZrO 2 sol containing Ag + ions when treated with either thermal annealing or with UV irradiation exhibit formation of Ag:ZrO 2 nanocomposite thin films via decomposition of Ag 2O 3 into metallic Ag. The formed Ag nanoparticles are found predominantly in spherical shape and density of Ag nanoparticles increases with increase in annealing duration for a particular concentration of Ag precursor. A protocol is provided to tailor the surface plasmon resonance-induced absorption peak at wavelength from 454 to 586 nm. These nanocomposite thin films show saturable absorption and exhibit high value of non-linear absorption coefficient.

Studies on the Growth, Optical, Thermal, and Mechanical Properties of Pure and o-Nitroaniline Doped Benzil Crystals

Pure and o-nitroaniline (O-NA) doped benzil single crystals were grown by the slow cooling solution growth method. The doping of O-NA is associated with the strong interaction between the guest and host molecules by the hydrogen bonding. Incorporation of O-NA in the lattice enhances the crystallinity. The nonlinearity increases due to the inductive nitro group added to the benzil. The values of nonlinear absorption coefficient (β) and nonlinear refractive index (n2) of benzil are −78 × 10−3 cm/W and −22 × 10−3 cm/W, while the corresponding values for O-NA doped benzil are −9.4 × 10−9 and −6 × 10−7 cm2/W, respectively. The figure of merit values of benzil and O-NA doped benzil are 2265 and 4990, respectively. The increase in hardness on doping of O-NA to benzil is due to the strong hydrogen bond.

Linear and third-order nonlinear optical absorption of amorphous Ge nanoclusters embedded in Al2O3 matrix synthesized by electron-beam coevaporation

Amorphous germanium (α-Ge) nanoclusters embedded in Al2O3 matrix are synthesized on fused-quartz glass substrate at room temperature by vacuum electron-beam coevaporation. Linear optical transmittance measurements reveal an indirect optical absorption edge with a blueshift as large as 1.6 eV due to the quantum confinement effects. The Z-scan method is used to study the third-order nonlinear absorption process of the synthesized samples, which clearly show a two-photon nonlinear process. Results also suggest that Ge nanocluster density or size is of great influence to the value of nonlinear absorption coefficient β.