Z-scan Method Research Articles

Linear and nonlinear optical properties of human hemoglobin.

In this study, we investigated the possibility of interactions between the solvent molecules with the Heme group in the human hemoglobin. The results of this study answer a key question: whether the interactions of the Heme unit with its surroundings are interdependent or independent of the protein units of human hemoglobin. Contributions of the intermolecular interactions were determined by exploiting the solvatochromism spectroscopic data by Kamlet-Taft (KAT) polarity functions. Solvent polarity effects on the nonlinear properties of the Heme's groups in the human hemoglobin (Hb) were investigated via the Z-scan method. The experimental results obtained with spectroscopic and nonlinear optical parameters (absorption coefficient and refractive index) show that the mechanism of solvation and the interactions of Heme are controlled by suitable configuration of the protein units of hemoglobin. In other words, interactions of the Heme with α- and β-globins are an effective factor in controlling the optical behavior of Heme.

Crystal growth, structural, optical and piezoelectric investigations on novel B4AAT (bis-4-acetylanilinium tartrate): A phase matchable second and third-order NLO single crystal for optoelectronic and nonlinear optical device applications

Abstract A novel organic nonlinear optical crystal, bis (4-acetylanilinium) tartrate (B4AAT) has been synthesized and successfully grown by a slow evaporation method using acetone as a solvent at ambient temperature. The single-crystal X-ray diffraction study reveals that B4AAT crystallized into a triclinic system with the noncentrosymmetric space group (P1). The crystalline perfection of the grown crystal was affirmed by the High-resolution XRD study. The characteristic functional groups with vibrational assignments and molecular structure of B4AAT were confirmed through Infrared, Raman and NMR spectroscopic analyses. UV–Vis–NIR spectral analysis of the crystal shows 69% of transmittance with a lower cut-off wavelength at 334 nm. The grown crystal was thermally stable up to 143.39 °C. The laser-induced damage threshold of the B4AAT compound was found to be 15.78 GW/cm2 for 1064 nm Nd: YAG laser radiation. The grown B4AAT possesses the low value of dielectric constant and piezoelectric charge coefficient (d33 = 5.86 pC/N) for the supercapacitor and microelectronics industry. The size-dependent of second harmonic generation efficiency of the crystal was found to be 4.6 times higher than that of KDP. The photoluminescence and lifetime measurements of the molecules in the crystal were studied by Fluorescence spectral analysis. The third-order nonlinear optical activity estimated utilizing the Z-scan method reveals that the B4AAT possesses saturable absorption, negative nonlinearity with self-defocusing and optical limiting effect. The aforesaid results confirm that B4AAT crystal is a potential candidate for optoelectronic and nonlinear optical device applications.

Ruthenium-Benzimidazole complex: Structural, optical and solvent-free catalytic studies

Two different applications namely catalytic oxidation under solvent free conditions and optical power limiting studies were done on a mixed ligand ruthenium complex containing benzimidazole moiety and Triphenylphosphine. The complex was evaluated for its potential catalytic activity on the alcohol oxidation reaction in presence of hydrogen peroxide (30% aqueous solution) as oxidant to synthesize the corresponding carbonyls and the highlight of the process was that the reaction proceeded without the presence of any solvent. Excellent selectivity was achieved by the Ruthenium catalyst Ru(L)PPh3Cl2 for conversion of aromatic alcohols to aldehydes under milder conditions. One another application namely the non-linear optical activity was also studied. This activity of the complex was extracted at 532 nm wavelength, by the Z-scan method. The experimental result displays strong nonlinear absorption in the ruthenium complex and found to be 15.55 cm/W concluding that the complex displays superior optical limitation.

Structural, dielectric and nonlinear properties of potassium hydrogen oxalate-trihydroxy boron (KHC2O4 B(OH)3) single-crystal

A metal-organic compound of potassium hydrogen oxalate-trihydroxy boron was grown by solution growth method. The solubility curve validates the positive temperature gradient of the compound. The polythermal method was used for the determination of the metastable zone width of the compound. The structure of the grown crystal was analyzed through single-crystal XRD. The occurrence of different functional groups within the sample was explained with the help of FTIR analysis. The optical analysis was carried out and the optical band gap energy of the compound was calculated. The third-order nonlinearity of the compound was analyzed with the help of the Z-scan method. The impedance analyzer was employed to analyze the value of dielectric loss and constant of the crystal.

Nonlinear absorption-induced transparency and extinction of boron nanosheets

Abstract Two-dimensional (2D) materials exhibit interesting nonlinear optical properties, and they have been used in bioimaging, ultrafast photon and all-optical switch devices. Boron nanosheets is a recently emerging 2D material that has attracted the attention of a large number of researchers. In this work, the saturation absorption (SA) effect of boron nanosheets has been investigated through a typical z-scan method, it is demonstrated that the nonlinear absorption coefficient and the quality factor are greatly improved compared with the other 2D materials such as black phosphorus, MoS2 and Ti3C2Tx. By combining the all-optical modulation and z-scan technology, the competition between the laser intensity-dependent SA and nonlinear scattering in boron nanosheets are revealed, and hence the optically-induced transparency and optically-induced extinction in nanosecond regime have been confirmed. Based on this competitive effect, an effective modulation of continuous light (λ = 671 nm) by nanosecond pulses (λ = 532 nm) has been realized, the maximum modulation depth of 5.5 dB is obtained.

Optimization of Nonlinear Optical Response of One-Dimensional Nanostructured Sodium Titanate Through Morphological Control

Nanostructured nonlinear optical (NLO) materials are attracting increasing interest as optical limiters for various applications. In this study, one-dimensional nanostructured Na2Ti3O7 was synthesized by a typical hydrothermal method and systematically characterized. The results showed that one-dimensional nanostructured Na2Ti3O7 has good crystallinity and thermal stability. Its morphology can be easily controlled to form nanotubes, nanobelts and nanorods by altering the amounts of added NaOH. The robustness of the NLO properties of one-dimensional nanostructured Na2Ti3O7 in broadband optical limiting (OL) applications was investigated by the open-aperture Z-scan method. At laser wavelengths of 532 nm and 1064 nm, the effective nonlinear extinction coefficients showed nonmonotonic dependence on the morphology; nanotubes gave the maximum value. The results confirmed that the NLO and OL responses of one-dimensional nanostructured Na2Ti3O7 can be effectively optimized by tailoring the morphology. In addition, the nonlinear extinction coefficients of these three types of one-dimensional nanostructured Na2Ti3O7 are better than those of multi-walled carbon nanotubes, a benchmark one-dimensional OL material, at 532 nm and 1064 nm; they therefore have potential applications in nonlinear optics. Nonlinear scattering and photothermal effect measurements showed that the OL shown by one-dimensional nanostructured Na2Ti3O7 can be mainly attributed to nonlinear scattering and free-carrier absorption at both irradiation wavelengths. The fabrication of one-dimensional nanostructured Na2Ti3O7 with different morphologies via this simple approach paves the way for the synthesis and tuning of new one-dimensional materials with desirable photonic properties for various applications.

Synthesis, molecular structural investigations, thermal, linear and nonlinear optical properties of a chalcone containing thiophene moiety by experimental and computation method

The chalcone (2E)-1-(3-bromothiophen-2-yl)-3-(2-methoxyphenyl)prop-2-en-1-one (2M3B2SC) has been synthesised. The experimental and theoretical, IR and proton NMR spectrum have been used to confirm the structure. The absorption, transparency and optical energy gap of the molecule were experimentally determined and compare with computed TD-DFT values. The thermal stability, MEP, NBO and FMOs of the molecule have been studied. The third order NLO properties and optical limiting threshold value have been measured by Z-scan method. The dipole moment, polarizability and hyperpolarizabilty values were calculated by TDHF method. The computed, static first and second hyperpolarizabilty values are 17 and 67 times the reference urea respectively.

Nonlinear optical absorption properties of InP nanowires and applications as a saturable absorber

Indium phosphide (InP) nanowires (NWs) have attracted significant attention due to their exotic properties that are different from the bulk counterparts, and have been widely used for light generation, amplification, detection, modulation, and switching, etc. Here, high-quality InP NWs were directly grown on a quartz substrate by the Au-nanoparticle assisted vapor-liquid-solid method. We thoroughly studied their nonlinear optical absorption properties at 1.06 μm by the open-aperture Z-scan method. Interestingly, a transition phenomenon from saturable absorption (SA) to reverse saturable absorption (RSA) was observed with the increase of the incident laser intensity. In the analysis, we found that the effective nonlinear absorption coefficient ( β eff ∼ − 10 2 cm / MW ) under the SA process was 3 orders of magnitude larger than that during the RSA processes. Furthermore, the SA properties of InP NWs were experimentally verified by using them as a saturable absorber for a passively Q -switched Nd : YVO 4 solid-state laser at 1.06 μm, where the shortest pulse width of 462 ns and largest single pulse energy of 1.32 μJ were obtained. Moreover, the ultrafast carrier relaxation dynamics were basically studied, and the intra-band and inter-band ultrafast carrier relaxation times of 8.1 and 63.8 ps, respectively, were measured by a degenerate pump–probe method with the probe laser of 800 nm. These results well demonstrate the nonlinear optical absorption properties, which show the excellent light manipulating capabilities of InP NWs and pave a way for their applications in ultrafast nanophotonic devices.

Size Dependence of the Resonant Third-Order Nonlinear Refraction of Colloidal PbS Quantum Dots

Due to their high resonant third-order nonlinear response, lead sulfide quantum dots (QDs) are potential materials for applications in the field of nonlinear optics. In this paper, we implement the Z-scan method to study the resonant nonlinear response of lead sulfide QDs in colloidal solutions. We managed to measure the purely intrinsic resonant nonlinear response, free of thermal contribution. We report that the lead sulfide QD third-order nonlinear response per QD shows an unconventional increase. A figure of merit for QD nonlinearity grows as a power function with a factor of 2.9.

Optical behaviour of nematic liquid crystal doped with carbon dot in the nonlinear optical regime

We delve into the effect of carbon dot (c-dot) doping at different concentrations (0.1, 0.2, 0.4, and 1 wt%) on the third order nonlinear optical properties of a nematic liquid crystal (NLC). C-dots were synthesized by the thermal decomposition of ammonium citrate salt. The size and morphology of prepared c-dots were confirmed by the TEM micrograph. Nonlinear optical properties of c-dot doped liquid crystal were investigated by the z-scan method using a Q-switched Nd: YAG laser delivering 7 ns pulse at 532 nm wavelength. A phenomenal increase in the nonlinear absorption coefficient, βeff, was observed for 0.2 wt% c-dot doped liquid crystal. There is an enhancement in the value of third order susceptibility, χ(3), of the order of 10 for the doped liquid crystal. An increase in the third order nonlinear optical absorption coefficient implies a better optical limiting characteristic than the pristine LC. The optical limiting threshold value of 0.2 wt% c-dot doped LC is found to be 1.23 J/cm2. We determine for the first time that c-dot doping in NLC leads to a significant improvement of the nonlinear optical properties compared to pure LC. The results indicate that the system under study could be a promising candidate for nonlinear photonic devices and optical limiters.

Third-order nonlinear optical properties of Ge-As-Te chalcogenide glasses in mid-infrared

Third-order nonlinear optical properties of Ge10AsxTe90-x chalcogenide glasses were investigated utilizing the Z-scan method at the mid-infrared wavelengths of 2.5 and 3.0 µm. The compositional dependence of the third-order nonlinearity was analyzed, and their correlation with the refractive index and the optical bandgap was discussed. The results show that nonlinear refractive index n2 can be significantly enhanced by the addition of tellurium, and larger n2 values are observed at 3.0 µm rather than 2.5 µm due to the two-photon resonance effect, and the maximum of n2 is 4.96 × 10−13 cm2/W at the composition of Ge10As20Te70. In addition, the experimental results are in good agreement with the semi-empirical Miller’s rule whilst the variation of dispersive n2 values are in relatively good coincidence with the theoretical model by Sheik-Bahae et.al. for direct bandgap semiconductors.

Third-order optical nonlinearity in silicon oxycarbide films

We study the third-order nonlinear optical properties of amorphous silicon oxycarbide (SiOxCy) films prepared by magnetron sputtering at room temperature and annealed in oxygen atmosphere at the temperature ranging from 200 °C to 600 °C. The third-order optical nonlinearity of the films was measured by Z-scan method at a wavelength of 1064 nm and a pulse duration 25 ps? The closed-aperture measurements show that the as-deposited films exhibit self-defocusing effect, while the annealed films present self-focusing behavior. The nonlinear refractive index is determined about |n2|~10−15 m2/W, which is four orders of magnitude larger than that of SiC crystals. The open-aperture results show that the as-deposited SiOxCy films and films annealed at 200 °C exhibit strong three-photon absorption behavior, while the SiOxCy films annealed at 400 °C and 600 °C exhibits nonlinear saturable absorption. The nonlinear absorption coefficients of films dependent on laser intensity are determined, and show saturable tendency. The results indicate that the third-order optical nonlinearity in SiOxCy films can be sensitively affected and tuned by the atom composition and microstructure, thus be of great significance for integrated nonlinear photonic devices.

2D tellurene/black phosphorus heterojunctions based broadband nonlinear saturable absorber

Abstract Two-dimensional (2D) mono-elemental materials (Xenes) show remarkable potential in the fields of fundamental science and technology, have been regarded as a wide range of building blocks for electronic technologies due to their unique chemical, physical, electrical, and optical properties. Here, 2D tellurene/black phosphorus (Te/BP) heterojunctions are successfully fabricated through liquid-phase exfoliation (LPE) method. Their nonlinear optical absorption properties at 1.0, 2.0, and 2.8 μm have been studied by an open-aperture Z-scan method. The results revealed the excellent broadband saturable absorption responses of the prepared BP/Te heterojunctions, which are further confirmed by using them as saturable absorbers (SAs) for passively Q-switched all-solid-state lasers operating at 1.0, 2.0, and 2.8 μm, respectively. In particular, 1.04 μm continuous-wave (CW) mode-locked lasers with a pulse width of 404 fs is realized for the first time, to our best knowledge. Our work indicates that 2D Xenes especially 2D Xenes based heterojunctions have great potential in the fields of pulsed laser generation/modulation and other optoelectronic and photonic devices.

Measurement of four-photon absorption in GaP and ZnTe semiconductors.

Intensity-dependent effective four-photon absorption (4PA) coefficients in GaP and ZnTe semiconductors were measured by the z-scan method using pump pulses of 1.75 µm wavelength, 135 fs duration, and up to 500 GWcm-2 intensity. A nonlinear pulse propagation model, including linear dispersion and 4PA was used to obtain the 4PA coefficients from measurements. The intensity-dependent effective 4PA coefficients vary from 2.6 × 10-4 to 65 × 10-4 cm5GW-3 in GaP, and from 3.5 × 10-4 to 9.1 × 10-4 cm5GW-3 in ZnTe. The anisotropy in 4PA was shown in GaP. The knowledge of 4PA coefficients is important for the design of semiconductor photonics devices.

Nonlinear optical properties of core shell type II quantum dot structures

In this study, CdSe/CdTe Type-II quantum dots (QDs) were synthesized using dropwise method. The core/shell nanocrystals have been characterized by UV–Vis absorption and photoluminescence (PL) spectroscopies, transmission electron microscopy and z-scan technique. Nonlinear properties of each type of quantum dots were studied using femtosecond(fs) z-scan method at 800 nm wavelength with different laser intensities. Fs laser z-scan experimental set-up are used to determine two photon absorption coefficient (β ̴10−12 cm/W) and nonlinear opticalKerrcoefficient (n2 ̴ 10−20 cm2/W. The imaginary and real parts of third order susceptibility (X(3)) were calculated based on β and n2 under different laser intensities for seven different core/shell QDs. Third order susceptibility for CdSe/CdTe type II QDs was found to be about 10−12 esu.

Glutathione-capped core-shell structured magnetite nanoparticles: Fabrication and their nonlinear optical characteristics

Core-shell structured magnetic Fe3O4@glutathione composite nanoparticles were synthesized and examined using diverse methods including Fourier-transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray analysis, transmission electron microscope, thermogravimetric analysis, and vibrating sample magnetometer analysis. In addition, the nonlinear optical measurements were performed by both open and closed aperture z-scan methods using an aqueous colloidal solution of the fabricated nanoparticles. The colloidal system exhibited a positive nonlinear refractive index because of the self-focusing effect arising from optical re-orientation. Although optical re-orientation is a rare phenomenon in nanocolloids, high polarizability of the enveloping organic ligands caused optical re-orientation of the composite nanoparticles in the electrical field direction of the incident beam. Finally, the effect of external voltage on the nonlinear optical index was further investigated.

Switch of Optical Nonlinear Absorption in Black Phosphorous

Nonlinear absorption of multi-layer black phosphorus nanosheets (BPs) were investigated using open aperture Z-scan method with 6 ns nanosecond laser pulses at 532 nm. It was found that, at lower intensities, BPs behave as saturable absorbers, but at higher intensities a shift from saturable absorption to reverse saturable absorption occurs. The transition process was analyzed in terms of the bleaching of ground-state and the excited-state absorption. We investigate the ultrafast dynamics by using pump − probe technique. The investigation implies that BPs has great potential applications in both mode-locking and optical liming in the visible range for ultrafast laser pulses.

Growth and characterization of efficient second-order nonlinear optical material: N-(2-chlorophenyl)-(1-propanamide)

The crystals N-(2-chlorophenyl)-(1-propanamide) (NCP) appropriate for nonlinear optical (NLO) and electro–optic appliances were grown full-fledged by the slow cooling method. The solubility and metastable zone width range of NCP specimen were studied. The specimen crystallizes in the monoclinic crystal system with noncentrosymmetric space group of P21. The crystal morphology study also elucidates supplementary excellence of the as-grown NCP crystal. The optical precision in the whole visible region was found to be superior for NLO claim. The crystallinity of the full-fledged crystal is determined by etching and HRXRD. Laser harm threshold and photoluminescence studies delegate the grown crystal comprises extremely less imperfections. The mechanical deeds of NCP sample at assorted temperatures were examined to decide the hardness solidity of the grown specimen. The piezoelectric behavior and the comparative second harmonic generation for assorted particle sizes of the material were also deliberate. The third-order nonlinear ocular possessions of NCP crystal specimen were determined by Z-scan method. The optical homogeneity of the solitary crystal was assessed using customized channel spectrum technique. The thermal structures of NCP solitary crystal have been studied using photopyroelectric method. The half-wave voltage of the full-fledged crystal was intended from the electro–optic experimentation. Photoconductivity nature of the grown crystal outlined consummate inducing dipoles due to strong incident radiation and further revealed the nonlinear deeds of the grown material.

Optical limiting property and ultrafast pump-probe study of two X-shaped oligomers with anthracene unit as a core

Two X-shaped multi-branched oligomers based on anthracene unit were studied by open-aperture Z-scan and ultrafast pump-probe methods to elucidate the nonlinear optical absorption properties as well as intramolecular charge transfer properties of typical X-shaped oligomers. Significant enhancement on the nonlinear optical absorption property was observed for the oligomer with triphenylamine groups as terminal end of each branch. Obvious optical limiting property was observed for these X-shaped oligomers and the mechanism was attributed to the two-photon absorption process. The ultrafast dynamic of these X-shaped oligomers exhibited a fast process about several ps to build an intramolecular charge transfer state, followed by a slow process longer than 100 ps which reflecting the evolution of the intramolecular charge transfer state.

Studies on semi-organic (C8H11NO)2[ZnCl4] single crystal for nonlinear optical (NLO) applications

Abstract Optically high quality metal-organic nonlinear optical (NLO) single crystals of bis(4-methoxybenzylammonium) tetrachloridozincate (4MBZ) have been harvested from the aqueous solution by solution growth technique. The single crystal X-ray diffraction (SXRD) results shows the grown 4MBZ crystal forms the monoclinic crystal system with space group of P21. Powder X-ray diffraction (PXRD) pattern has been recorded in the 2θ range of 10–60° to confirm the various types of crystalline planes and phase purity. The Hirshfield surface on 4MBZ has been carried out to finding intermolecular interactions. From the Fourier transform infrared (FTIR) spectroscopy analysis, the functional groups were confirmed. The optical transparency and band gap energy of the crystal were studied by the UV–Vis NIR spectral studies. Resultant, the grown crystal has good optical transparency in the entire visible and near IR region. The grown 4MBZ crystal sample was subjected to Thermogravimetric analysis (TGA) and differential Scanning colorimetry analysis (DSC) were carried out to study the thermal behaviour. The chemical etching analyses was carried out to finding dislocation density. The nonlinear parameters such as nonlinear refractive index (n2), absorption coefficient (β) and third order nonlinear susceptibility (χ(3)) have been analyzed by Z-scan method using diode laser 532 nm.