Values Of Nonlinear Absorption Coefficient Research Articles

Determination of third order nonlinearity (n2 & β) of glycine zinc sulphate pentahydrate semi-organic single crystal using two laser radiations at different intensities

AbstarctThe third order nonlinear optical properties i.e. nonlinear refraction (n2), absorption coefficient (β) and third order susceptibility χ(3) of glycine zinc sulphate pentahydrate (GZS) semi-organic single crystal was investigated under the excitation of Q-switched Nd-YAG laser pulsed radiations (λ = 532 nm & 1064 nm) by familiar Z-scan method. The values of nonlinear refraction (n2), at 532 nm were 1.19 × 10−5 (cm2/GW), 2.09 × 10−5 (cm2/GW), 2.27 × 10−5 (cm2/GW), 2.48 × 10−5 (cm2/GW), and 2.55 × 10−5 (cm2/GW) at incident optical beam intensities of 0.76 (GW/cm2), 1.13 (GW/cm2), 1.17 (GW/cm2), 1.63 (GW/cm2) and 1.88 (GW/cm2) respectively while that of values at 1064 nm were 4.31 × 10−5 (cm2/GW), 4.69 × 10−5 (cm2/GW), 5.41 × 10−5 (cm2/GW) and 6.39 × 10−5 (cm2/GW) at incident optical beam intensities of 1.20 (GW/cm2), 1.25 (GW/cm2), 1.32 (GW/cm2) and 1.38 (GW/cm2) respectively. The values of nonlinear absorption coefficient (β) at 532 nm were −1.45 (cm/GW), −0.79 (cm/GW), −0.5 (cm/GW), 0.12 (cm/GW) and 0.64 (cm/GW) at incident optical beam intensities of 0.76 (GW/cm2), 1.13 (GW/cm2), 1.17 (GW/cm2), 1.63 (GW/cm2) and 1.88 (GW/cm2) respectively while that of values at 1064 nm were 0.62 (cm/GW), 0.74 (cm/GW), 0.77 (cm/GW) and 0.81 (cm/GW) at incident optical beam intensities of 1.20 (GW/cm2), 1.25 (GW/cm2), 1.32 (GW/cm2) and 1.38 (GW/cm2) respectively. The values of third order susceptibilities χ(3) at 532 nm were 0.83 × 10−12 (esu), 1.32 × 10−12 (esu), 1.42 × 10−12 (esu), 1.55 × 10−12 (esu) and 1.56 × 10−12 (esu) at intensities of 0.76 (GW/cm2), 1.13 (GW/cm2), 1.17 (GW/cm2), 1.63 (GW/cm2) and 1.88 (GW/cm2) respectively while that of values at 1064 nm were 2.71 × 10−12 (esu), 2.96 × 10−12 (esu), 3.4 × 10−12 (esu) and 4.02 × 10−12 (esu) at incident optical beam intensities of 1.20 (GW/cm2), 1.25 (GW/cm2), 1.32 (GW/cm2) and 1.38 (GW/cm2) respectively. It was seen that the sample showing saturable absorber to reverse saturable absorber at 532 nm wavelength at incident optical beam peak intensity (I0) of 1.53 GW/cm2. Thus the crystal could be a potential candidate of optical switching application. It was also seen that the material possess positive nonlinearity. It was also found that the values of nonlinear absorption coefficient (β) and nonlinear refraction (n2) increase with increase of excitation intensity irrespective of excitation wavelengths.

Investigating the optical and magnetic properties of engineered multifunctional graphene oxide and potential application in medical physics and nonlinear optics‏

Herein, the synthesis of multifunctional engineered GOs with the structure of GO@Fe3O4-ligands-CdTe quantum dots (QDs) by an environment-friendly aqueous method was reported. l-cystein (Cys), 3-trimethoxysilyl-propanethiol (TMSP), and glutathione (GSH) were selected as ligands. The as-prepared GO@Fe3O4-ligands-CdTe QDs hybrid nanostructures were characterized by different methods. The findings indicate that the nanocomposites of GO@Fe3O4–ligands–CdTe QDs demonstrate superparamagnetic properties at room temperature. The saturation magnetization values for GO@Fe3O4, GO@Fe3O4-Cys-CdTe, GO@Fe3O4-GSH-CdTe, and GO@Fe3O4-TMSP-CdTe, are 25, 14, 16, and 2 emu g−1, respectively. These nanocomposites show stable and strong luminescence at 580-600 nm. The magnetic nanostructures also reveal the absorption wavelength at 300-490 nm. Using TMSP ligand as a bridge between QDs and magnetic GOs, the luminescence of the nanostructure has not decreased much compared to CdTe QDs. The use of Cys ligand preserves the saturation magnetism of the nanocomposite more than magnetic GO, and the dispersed nanostructure is stable in water. Furthermore, the transverse and longitudinal optical (TO and LO) phonon modes of prepared GO@Fe3O4–ligands–CdTe QDs were obtained by Kramers-Kronig (KK) relations based on fourier-transform infrared (FTIR) spectroscopy. The Z-scan results show that the type of used ligand has a great effect on the nonlinear optical (NLO) properties of the final product. The largest NLO parameters are related to GO@Fe3O4- TMSP -CdTe QDs, and the values of nonlinear absorption coefficient and nonlinear refractive index were obtained as 2.17×10−3(cm/W) and10.27×10−8(cm2/W), respectively. As a result, GO@Fe3O4–ligands–CdTe QDs nanostructures can be considered as promising multifunctional nanostructures for various biomedical applications and NLO devices.

Structural correlation to linear and non-linear optical properties of Bi3+ ion doped Li2O–SrO–B2O3 glasses: Optical switching and limiting applications

A series of bismuth doped lithium strontium borate glasses are synthetized using melt-quench technique. Compositional modification resulted in the maximum refractive index (2.306) and lowest optical bandgap (3.36 eV) for 2 mol% of Bi2O3. Raman as well as FTIR investigations reveal the presence of diborate, dipentaborate and metaborate ring type structural units and structural interconversions occur between diborate and metaborate rings. These structural interconversions are in support of the trends observed in linear and non-linear optical properties. Photoluminescence spectra reveal a prominent emission peak around 572 nm corresponding to the 2P3/2 → 2P1/2 transition. Commission Internationale de I'Eclairage (CIE) and correlated colour temperature (CCT) studies indicate the glasses emit greenish-yellow light around 7172 K. Z-scan approach is utilised to examine non-linear optical properties with a nanosecond pulsed laser operating at 532 nm. Z-scan investigation revealed good optical nonlinearity in all the glasses. Open aperture normalized transmittance spectra is used to evaluate the values of non-linear absorption coefficient (ꞵ) and optical limiting. ꞵ is in the range of 0.42–3.2x10−10 mW−1 and optical limiting values are in the range of 1.642–2.078x1012 Wm−2. Z-scan studies reveal RSA and RSA to SA (W- patterns) which suggests that the investigated glasses show saturable absorption (SA) as well as reverse saturable absorption (RSA) pattern. According to these findings, the glasses under investigation are promising materials for solid state lasers, greenish-yellow LEDs, compositional tuning optical switching and limiting applications.

Effect of Ba/Sr ratio on the nonlinear optical properties of Ba1-xSrxTiO3 (x = 0.1–0.9) thin films

Perovskite-structured barium strontium titanate (Ba1-xSrxTiO3, x = 0.1–0.9) films have been epitaxially fabricated by using a pulsed-laser deposition technique. The third-order nonlinear optical properties were studied through a z-scan method, allowing the resolution of the nonlinear refractive and absorptive contributions to the responses. Although all the samples show almost the same value of nonlinear absorption coefficient, the extracted nonlinear refractive index of the sample of x = 0.3 is apparently larger than that of other samples. Dependency of the nonlinear optical properties on the Ba/Sr ratio is discussed in terms of the crystal phase transformation and metal-oxygen bond length of the selected materials.

Influence of nitro group on solvatochromism, nonlinear optical properties of 3-morpholinobenzanthrone: Experimental and theoretical study

We report the synthesis of 3-morpholino-9-nitrobenzanthrone (NMB) dye. By using FT-IR, 1H NMR, and X-ray crystallography, we characterized the molecular structure of the synthesized dye. The structural features of the dye were compared to those of an identical dye without nitro substituents. The push pull kind of benzanthrone dye (NMB) was examined for solvent-dependent photophysical properties. NMB exhibits a large Stokes shift. The polarity plots indicate that hydrogen-bonding interactions are influential in most of the solvents. Detailed structural analysis as well as one-photon absorption and emission process was computationally investigated for both the molecules. NMB exhibits significant two photon absorption (TPA) activity at various electron transitions ranging from visible to NIR regions. Further, Nonlinear absorption coefficient was calculated for the dye samples from the open aperture Z-scan data. The nonlinear absorption coefficient values were obtained for the dye samples for input laser pulse energies ranging from 5 to 20 µJ. The results decipher that these dye samples are prospective contenders for the fabrication of optical limiter devices. Nitro substituents at the active site enhance charge transfer, thereby enhancing the NLO response.

Above bandgap one-photon excitation induced nonlinear absorption behavior of InTe

In an attempt to investigate the nonlinear absorption properties of amorphous InTe semiconductors, three different thicknesses of 30 nm, 60 nm and 90 nm thin films were deposited by the vacuum evaporation method. Bandgap energies and Urbach energies were obtained from the linear absorption spectrum. While the change in thickness and doping led to slight changes in bandgap energies as 0.08 eV, significant increases in Urbach energies were obtained for thicker and doped films. A theoretical model accounting one photon absorption, excited state absorption, and saturation of each process was utilized to derive the transmittance in open aperture Z-scan data. The values of nonlinear absorption coefficient and saturation intensity threshold were obtained from the model and the interplay between excited state absorption and saturable absorption was explained by proposing an energy band diagram containing the contribution of defect states to the nonlinear absorption behavior of amorphous semiconductors.

Layer-Dependent Nonlinear Optical Properties of WS2, MoS2, and Bi2S3 Films Synthesized by Chemical Vapor Deposition.

Two-dimensional (2D) layered materials have shown layer-dependent optical properties in both linear optical and nonlinear optical (NLO) regimes due to prominent interlayer coupling and quantum confinement in an atomic scale. However, the NLO properties become more complicated as both saturable absorption (SA) and reverse saturable absorption (RSA) easily happen in 2D materials, which results in a significant challenge to understand the evolution of nonlinear absorption with layers. Motivated by this, chemical vapor-deposited chalcogenide compounds (WS2, MoS2, and Bi2S3) are used to investigate the pump intensity and layer number-dependent NLO properties. The values of nonlinear absorption coefficients of these chalcogenide compounds increase with the pump intensity by an 800 nm femtosecond laser, which can be described by an empirical power law function. The SA process due to the large transition probability of the ground state readily takes place in thick samples, while RSA occurs easily in thin samples due to the two-photon absorption (TPA). The transition from TPA to SA is deduced to occur at 13L-WS2, 15L-MoS2, and 5L-Bi2S3, which is related to the layer-dependent band gaps. Our results provide an efficient way to tune optical nonlinearities with a controlled layer number and to design corresponding NLO devices such as optical switches and saturable absorbers.

The effect of aromatic and non-aromatic ionic liquids on the optical nonlinearity responses of porphyrins

The effects of adding aromatic and nonaromatic ionic liquids (ILs) on third-order nonlinear optical (NLO) responses of 5,10,15,20-Tetrakis(4-methoxycarbonylphenyl) porphyrin (S1) and [5,10,15,20-Tetrakis(4-methoxycarbonylphenyl)-porphyrin]–Co (II) (S2) at 532 nm were investigated using the Z-scan technique. ILs show negligible nonlinear response in compare with porphyrins. A significant increase in NLO response with adding DABCO-based IL to S1 was observed which approximately equal to Cobalt(II) ion substitution at the core of porphyrin structure. The obtained value of nonlinear absorption coefficient β (cm/W) and the nonlinear refractive index n2 (cm2/W), are of the order of 10−4 and 10−8, respectively. The positive synergetic effects were interpreted for enhanced nonlinear optical response by adding imidazolium-based IL and Cobalt(II) ion substitution at the core of porphyrin structure. Using ILs as additive led to excellent nonlinear properties which implies their promising applications in the optical devices.

Defect assisted nonlinear absorption and optical limiting in amorphous TlGaS2(1-x)Se2(x) (0 ⩽ x ⩽ 1) thin films

In an attempt to investigate the effect of band gap energy and defect states on nonlinear absorption, 80 nm thick amorphous TlGaS2(1-x)Se2(x) thin films with different compositions (0 ⩽ x ⩽ 1) were deposited by vacuum evaporation method. Band gap energies and Urbach energies were obtained from linear absorption spectra. The change in composition led to 0.24 eV increase in band gap energy and 0.32 eV increase in Urbach energy. A theoretical model incorporating one photon absorption, two photon absorption, free carrier absorption and saturation of each absorption process was applied to derive the transmittance in open aperture Z-scan data. The values of nonlinear absorption coefficient and saturation intensity threshold were obtained from the model and two different nonlinear absorption coefficient variation behaviors were observed with increasing Se composition (x) in amorphous thin films based on the opposite contributions of decreasing band gap energies and decreasing Urbach energies on nonlinear absorption.

Enhanced nonlinear and thermo optical properties of laser synthesized surfactant-free Au-Pt bimetallic nanoparticles

The Au and Pt nanoparticles were synthesized employing laser ablation in water. Ligand-free Au-Pt bimetallic nanoparticles were generated by means of laser irradiation of the colloidal mixture of Au and Pt nanoparticles. The nonlinear optical characteristics like nonlinear absorption coefficient, nonlinear refractive index, optical limiting threshold and non linear optical susceptibility of Au, Pt, their colloidal mix and bimetallic nanoparticles were determined via Z scan method. All nanoparticle samples exhibited strong reverse saturable absorption behaviour with positive value of nonlinear absorption coefficient and strong optical limiting efficiency. The non linear absorption and refraction characteristics were found to be considerably enhanced for the Au-Pt bimetallic nanoparticles than the corresponding mono metallic nanoparticles and the pre-irradiation colloidal mix. The thermo optical features were also studied using thermal lens method and found to be tunable by controlling the fraction of Au and Pt in the bimetallic nanoparticles. To the best knowledge of the authors, it is presumed that, the present work is the first report on the non linear and thermo optical characterization of Au-Pt bimetallic nanoparticles. The present work has significance in nonlinear optical and photo thermal applications like optical limiting, photo thermal therapy and photo acoustic imaging.

Synthesis Bioactivities and Non-linear Optical Behavior of Angularly and Linearly Fused Pyridazino Quinoline Derivatives

Angularly and linearly fused pyridazino quinolines has been reported via the cyclisation of hydrazino quinoline with chloroacetyl chloride. The structure was characterized by IR and NMR studies. The synthesized chemical compounds were applied against 2 gram-positive bacteria and 2 gramnegative bacteria by the well diffusion method. The entire synthesized compounds exhibited different degrees of antimicrobial activity at concentrations between 20–100 μg/disc against the test organisms. Antioxidant studies were also performed against DPPH radical and the results were attractive. In vivo anti-inflammatory and analgesic screening was also done for selected drug and the results were desirable. Quantum chemical calculations were performed using the DFT B3LYP method in the 6-31G (d, p) basis. Non-linear optical behavior of the compounds was analyzed by with first hyperpolarisability. The non-linear optical properties of solution of compound in DMSO solvent has been investigated using Z-scan technique with femto second. The calculated value of non-linear absorption coefficient displayed the non-linearity of the molecule. The in silico ad instrumental results showed that the compounds are attractive molecules for future application in non-linear optics.

Investigations on nonlinear optical properties and thermal diffusivity of gold nanoparticle embedded protein complex

We investigate the modifications in nonlinear optical response and thermal diffusivity of three proteins, viz. Bovine Serum Albumin (BSA), Human Serum Albumin (HSA), and Hen Egg White Lysozyme (HEWL) induced by gold nanoparticles (GNPs) interaction using a single beam z-scan technique and a dual-beam thermal lens technique respectively. Varying concentrations of chemically synthesized gold nanoparticles were added to a fixed concentration of proteins. The size and morphology of gold nanoparticles were analyzed using TEM analysis. The stability of protein-gold nanoparticles was established using zeta potential analysis. The absorption spectra confirmation of a ground state complex between the proteins and gold nanoparticles. The third-order nonlinear optical properties of the samples suggest that proteins exhibit two-photon absorption and reverse saturable absorption. The observed values of nonlinear absorption coefficient and imaginary part of nonlinear susceptibility χ3 for protein-gold nanoparticles are of the order of 10−10 m/W and 10−19 m2/V2. With the increase in gold nanoparticle concentration, both these values are found to decrease due to the formation of the ground-state complex as is evident from absorption spectra. This indicates that gold nanoparticle concentration plays an important role in modulating the nonlinear optical response of the proteins. The nonlinear optical properties of the samples at varying input fluence and wavelength were also investigated. The work is important as it finds application in photothermal therapy for cancer treatment. The optical limiting threshold of the samples is found to decrease with an increase in the concentration of gold nanoparticles. Results suggest that protein-gold nanoparticles can serve as potential candidates for optical limiting applications. Thermal diffusivity values were found to decrease with an increase in gold nanoparticle concentration. Also, a linear variation of thermal diffusivity was obtained with an increase in protein concentration and is a possible method for sensing protein concentration in blood samples.

Growth and Z-scan analysis of semi-organic Bis(picolinic acetate) Zinc(II) single crystal for third order NLO applications

Here, we report a new semi-organic single crystal namely Bis(picolinic acetate) Zinc(II) (BPZ) which was grown by a conventional slow evaporation method at room temperature. Structural studies were carried out by single crystal XRD and the results show that Bis(picolinic acetate) Zinc(II) belongs to monoclinic crystal system with space group P21/n. The presence of functional groups in the grown crystal was identified by FTIR spectral analysis. UV-Vis spectral studies reveal that the grown crystals are transparent in the wavelength region of 200-1200 nm. In order to analyze the mechanical strength of the grown crystal, Vickers micro hardness tester was employed. The dielectric properties with respect to different frequency at room temperature were also studied to analyze the dielectric response. The third order nonlinear optical properties were determined by Z-scan studies which shows significant higher values of nonlinear absorption coefficient (β) and third order nonlinear susceptibility (χ3). The enhanced third order nonlinear behavior suggests that the title compound is suitable for nonlinear optical applications.

Resonant and Non-resonant Nonlinear Optical Properties of Er3+ modified BaO-ZnO-B2O3 Glasses at 532 and 1550 nm

Er2O3 doped Barium-Zinc-Borate glasses with compositions xEr2O3-(100-x)[0.1BaO-0.4ZnO-0.5B2O3]; x = 0.5, 1.0, 1.5 and 2.0 have been prepared by melt quench technique. The amorphous nature of glasses has been ascertained by X-ray diffraction patterns. Fourier Transform Infrared (FTIR) spectra of the prepared glasses indicate that Er2O3 acts as glass modifier. With the increase in Er2O3 content, BO4 structural units start converting into BO3 structural units. The values of optical energy band gap (Eg) are observed to decrease with the increase in Er2O3 content. The values of nonlinear absorption coefficient (β) and nonlinear refractive index (n2) have been estimated by fitting of experimental data with theoretical models and both are found to increase with the increase in Er3+ ions concentration at 532 nm as well as 1550 nm excitation wavelengths. The calculated values of total third order nonlinear susceptibility (χ(3)) are observed to increase with the increase in Er3+ ions concentration.

Preparation, characterization and study on the nonlinear optical parameters of novel biphenyl-4-carbohydrazide derivative

We report here the preparation, characterization and the 3rd order nonlinear optical properties of (N-[(E)-(3-Nitrophenyl) methylidene]) biphenyl-4-carbohydrazide, a novel organic NLO material. The characterization of the compound for molecular structural study was carried out by FTIR and X-ray Diffraction. A Photoluminescence and UV–vis spectrum was selected to study the linear optical properties. In dimethyl formamide (DMF) solution, the 3rd order NLO properties have been measured at 532 nm by DPSS continuous wave laser using the Z-scan technique. Open aperture data indicates the presence of two photon absorption (TPA) at 532 nm. The measured experimental values of nonlinear absorption coefficient (β) is 10-8 (cmW−1), the nonlinear refractive index(n2) is 10-11(cm2W−1), and third order susceptibility (χ(3)) is 10-9esu. Due to TPA at 532 nm the compound shows good optical limiting behavior. The values obtained are comparable with the values obtained for 4- methoxy chalcone derivatives and dibenzylidene acetone derivatives. The optical limiting threshold of the compound is 2.8 KJ/cm2 .The comparatively high value obtained indicates that this material may be used in optical device applications like optical limiters and optical switches.

Thermal annealing and dopant dependence of nonlinear absorption characteristics in ZnO Nanoparticle/PMMA films

Cr and Sb doped ZnO/PMMA nanocomposite films were investigated to understand the effect of doping and annealing on linear and nonlinear optical properties. ZnO, ZnO:Cr and ZnO:Sb nanoparticles were synthesized by hydrothermal method. The structural results showed that the incorporation Cr and Sb dopant to the ZnO crystal lattice led to decreasing of the crystallite sizes from 30.3 nm to 24.4 nm due to the increasing of the number of defect states inside the energy band gap. The crystallite size of the synthesis nanoparticles increased with annealing due to the decreasing defects in the band gap. The band gap energies were estimated to be 5.240 eV, 5.260 eV, 5.246, 5.253 eV and 5.280 eV for undoped, Cr and Sb doped ZnO/PMMA nanocomposite films, respectively. After annealing, the band gap energies decreased to 2.505 eV, 2.510 eV, 2.610 eV, 2.755 eV and 2.597 eV values due to the increasing of the crystallite sizes of the nanoparticles, respectively. The transmittances of the films varied with Cr and Sb doping and annealing process. The open aperture Z-scan technique was used to measure the nonlinear absorption properties of investigated films at ns regime. The nonlinear absorption coefficient values were found to be 4.95 × 105 cm/GW, 7.21 × 105 cm/GW, 1.69 × 106 cm/GW, 8.18 × 105 cm/GW and 2.09 × 106 cm/GW for ZnO/PMMA, ZnO:Cr/PMMA and ZnO:Sb/PMMA nanocomposite films, respectively. The saturation intensity thresholds increased with doping from 5.15 GW/cm2 to 10.40 GW/cm2. After annealing, the nonlinear absorption coefficient values were found to be 2.14 × 105 cm/GW, 2.99 × 105 cm/GW, 4.85 × 105 cm/GW, 3.43 × 105 cm/GW and 6.91 × 105 cm/GW for ZnO/PMMA, ZnO:Cr/PMMA and ZnO:Sb/PMMA, respectively.

Nonlinear optical absorption and refraction properties of fluorinated trans-dicationic pyridinium porphyrin and its metal complexes

Here, we present the experimental investigation on the third order nonlinear optical properties of a series of fluorinated trans-dicationic pyridinium porphyrins namely, 5,15-di(pentafluorophenyl)-10,20-bis(4-N-methylpyridyl) porphyrin and its Cu(II) and Zn(II) derivatives, using single beam Z-scan method with nanosecond pulses at 532 nm. The major contribution to the absorptive nonlinearity exhibited by these porphyrins comes from excited state absorption assisted reverse saturable absorption. The value of nonlinear absorption coefficient is found to be maximum for the Zn(II) complex and is attributed to the extended delocalization due to heavy atom effect. Optical limiting efficiency is also found to be enhanced for Zn(II) porphyrin, with a limiting threshold value of 1.89 J/cm2, which indicates its potentiality as an optical limiter for the smart filtering of optical energy in direct viewing systems. Considering the dispersive contribution to the optical nonlinearity, self defocusing effect is observed in all porphyrins and the magnitude of nonlinear refraction coefficient is obtained as higher in free base porphyrin than that in the metalated compounds. The weakest negative nonlinear effect in Zn(II) porphyrin is attributed to the interplay between the coordination interaction and the thermal effects.

The effect of doping and annealing on the nonlinear absorption characteristics in hydrothermally grown Al doped ZnO thin films

The effects of annealing and Al dopant on the nonlinear absorption characteristics of amorphous ZnO thin films were studied experimentally and theoretically. The structural patterns of AZO thin films grown at various growth temperatures (80ᵒC, 90ᵒC, 100ᵒC) and Al doping ratios (%5, %10, %20) were determined by using x-ray diffraction. The results revealed that the crystallinity increased with increasing growth temperature and Al doping ratio. The optical band gap decreased from 3.91 to 3.78 eV and the transmittance of AZO thin films decreased from 90% to 55% with increasing Al molar ratio. The open aperture Gaussian beam Z-scan measurements indicated that all studied films exhibited nonlinear absorption behavior due to the defect states inside energy bandgap. The nonlinear absorption coefficients increased from 1.34 × 10−4 to 6.12 × 10−4 cm/W for 4 ns pulse duration with increasing of doping concentration. The experimental curves were fitted to the theory of open aperture Gaussian beam Z-scan based on the Adomian decomposition method to obtain nonlinear absorption coefficients along with saturation intensity thresholds. In order to investigate the effect of free carrier absorption, the OA Z-scan experiments were also performed for 65 ps pulse duration. The nonlinear absorption coefficients were found to be 0.58 × 10−4, 1.81 × 10−4 and 3.29 × 10−4 cm/W for 65 ps pulse duration. For nanosecond pulse durations, the obtained nonlinear absorption coefficient values of thin films are bigger than the values of picosecond pulse durations due to the greater contribution of free carrier absorption. Increasing annealing temperature from 100ᵒC to 400ᵒC leads to decreasing nonlinear absorption coefficients owing to decreasing localized defect states.

Z-scan study of nonlinear absorption in gold doped borosilicate glass: Effect of Dy3+

Nonlinearity is one of the most important optical properties widely used in opto-electronic devices. In this work, the optical nonlinearity of a series of Bismuth Borosilicate glasses is compared. The glasses prepared through conventional melt-quench technique comprises of Dy2O3, gold nanoparticles (GNPs) and both Dy2O3 and GNPs. XRD is used to confirm the amorphous nature of the glass whereas FESEM is carried out to observe variation in morphology of GNPs with the addition of Dy2O3. Effect of Dy2O3 on particle size is recorded using HRTEM. DTA is carried out to observe the variation in thermal behaviour of the material. The highest value of nonlinear absorption coefficient (4.35 × 10−12 cmW−1) and third order nonlinear optical susceptibility of 8.68 × 10−9 esu are observed from Z-scan for the glass containing both Dy2O3 and GNPs. The results conclude that the addition of Dy2O3 enhances the nonlinearity of glass containing gold and thus has promising applications in optical devices.

Effect of Charge and Dielectric Constant on Linear and Nonlinear Optical Properties of Two Dyes

The enhancement of nonlinear optical properties of dye with surfactant can be applied in photodynamic therapy and medicine. The nonlinear optical properties of alizarin red S and rhodamine B mixed with cationic and anionic surfactant are studied by Z-scan technique. The nonlinear absorption coefficient values of cationic dye (rhodamine B) in aqueous solution are reduced with the increase of anionic surfactant concentration, while the nonlinear absorption coefficient values are enhanced by the interaction between anionic dye (alizarin red S) with anionic surfactant. The nonlinear refractive index (n2) of cationic and anionic dye is reduced with an increase of surfactant concentration. The nonlinear absorption coefficient values of a rhodamine B-doped droplet is reduced by the increase of cationic surfactant in the water droplet. In general, the nonlinear absorption coefficient values are reduced with an increase of dye solubility, and the value of n2 is reduced with an increase of dye solubility in solution. The fluorescence intensity is higher when dye and surfactant have the same charge. This effect can be due to the increase of solubility of cationic (anionic) dye with an increase of anionic (cationic) surfactant in the solution. The reduction of nonlinear absorption coefficient values with an increase of droplet size can be due to the change of rhodamine B solubility in microemulsion.