Refractive Nonlinear Coefficient Research Articles

Impact of Se doping on optical and third-order nonlinear optical properties of spray pyrolysis fabricated CdS thin films for optoelectronics

Cadmium sulphide is known to have tremendous applications towards optoelectronic and nonlinear devices. Hence, here we have facilely casted the CdS films with diverse Se contents through low-cost spray pyrolysis technique. XRD study defends mono-phase formation of CdS having hexagonal system at all Se doping contents. Scherrer equation was employed to evaluate crystallite size in range of 15–25 nm. Vibrational study reveals the presence of fundamental modes of vibration of hexagonal CdS. EDX and SEM mapping studies approve the existence of Se and its homogeneous distribution all over the film. SEM micrographs shows the nanoscale grains formation on film surface and the size is increasing with Se doping. Optical study revealed that the grown films are of optimal quality with transparency in range of 60–75% with low absorbance and reflectance values. The refractive index values are noted to varied from 1 to 2.7 with wavelength and noticed to be reduced on Se content in UV–Vis region. The reduction in direct and indirect energy gap was found from 2.46 to 2.34 eV and 2.21 to 1.96 eV, correspondingly due to Se. PL emission profile contains an emission band at 528, 529, 529, 530 and 546 nm for 0.0, 0.5, 1.0, 2.5, 5.0 wt% Se:CdS films. Dielectric constant and loss were estimated. The nonlinear refraction (n2) and absorption coefficient (β) and third-order nonlinear susceptibility $$(\chi^{3} )$$ values were determined using Z-scan and observed in order of 10–8 cm2/W, 10–4 cm/W and 10–3 esu, correspondingly. The high values of $$\chi^{3}$$ propose the films for nonlinear applications.

Nonlinear optical properties of neutral red dye: Enhancement using laser ablated gold nanoparticles

Gold nanoparticles were prepared by the method of laser ablation and studied its effects on the optical properties of neutral red dye. The linear absorption intensity of the dye was found to be slightly increased in the presence of gold nanoparticles. The third order nonlinear optical properties were investigated using Single beam Z-scan technique in nanosecond regime. In open aperture mode, the samples exhibited a combined behavior of saturable absorption and reverse saturable absorption characteristics. The closed aperture mode studies revealed the negative nonlinearity of the samples. Different nonlinear optical parameters such as the nonlinear absorption and refraction coefficients and the third order nonlinear optical susceptibility were determined. In the presence of gold nanoparticles, the nonlinear optical properties of neutral red dye enhanced significantly and this is explained on the basis of increased local field effects produced by the gold nanoparticles.

Diffraction Rings Pattern and Nonlinear Optical Properties of Hybrid ZnO-NPs / Epoxy Resin

In this research, the diffraction ring patterns scan and single-beam Z-scan techniques were used to measure the nonlinear refractive index (n2) and nonlinear absorption coefficient (β). Nano-composite sample, which consists of zinc oxide nanoparticles (ZnO-NPs), and epoxy resin polymer. The sample was prepared by the casting method. A second harmonic generation Nd: YAG laser, which operates at 532 nm and intensity 3183 W/cm2 was used for the two techniques. Z-scan results showed that values for nonlinear refractive index n2 and nonlinear absorption coefficient β were obtained of 6.59*10-9 cm2/W and 1.75*10-3 cm/W respectively. While results for the D-scan technique showed that the number of rings increases with the increasing of laser power.

Spatial self-phase modulation in WS2 and MoS2 atomic layers

Laser field-induced spatial self-phase modulation (SSPM) in WS2 and MoS2 atomic layer liquid suspensions displayed the diffraction profile of concentric rings at the far-field due to the coherent superposition of transverse wave vectors with characteristic spatial nonlinear phases. The evolution of the number of rings indicated the spatial alignment of anisotropic atomic layers in the liquid base solution. The intensity-dependent number of symmetric rings revealed the nonlinear refraction coefficients of MoS2 and WS2 atomic layers which were estimated to be ∼ −1.96 × 10−16 m2/W and ∼ −1.11 × 10−16 m2/W, respectively. The central interference profile and the diffraction pattern identified the negative polarity of nonlinear refraction. The vertically asymmetric diffraction ring indicates the phase distortion of optical field due to the heat convection.

Enhanced Nonlinear Optical Coefficients of MAPbI3 Thin Films by Bismuth Doping.

The poor photostability under ambient conditions of hybrid halide perovskites has hindered their recently explored promising nonlinear optical properties. Here, we show how Bi3+ can partially substitute Pb2+ homogeneously in the commonly studied MAPbI3, improving both environmental stability and photostability under high laser irradiation. Bi content around 2 atom % produces thin films where the nonlinear refractive (n2) and absorptive coefficients (β), which modify the refractive index (Δn) of the material with light fluence (I), increase up to factors of 4 and 3.5, respectively, compared to undoped MAPbI3. Higher doping inhibits the nonlinear parameters; however, the samples show higher fluence damage thresholds. Thus, these results provide a road map on how MAPbI3 can be engineered for practical cost-effective nonlinear applications by means of Bi doping, including optical limiting devices and multiple-harmonic generation into optoelectronics devices.

Third order nonlinear optical properties of gold/alumina multilayer nanocomposites with different nanoparticle arrangements

The linear and nonlinear optical properties of gold nanoparticle/alumina matrix multilayer nanocomposites obtained by successive laser deposition were studied. The nonlinear optical properties of the gold nanoparticle layers embedded in alumina were determined by Z-scan at 532 nm, using a picosecond pulse laser. The linear absorption, third-order nonlinear absorption and refraction were found to depend on the arrangement of gold nanoparticles in the nanocomposite thin film, when essential characteristics such as nanoparticle dimension, metal concentration and total film thickness are constant. When partial self-correlation between gold nanoparticles in successive layers occurs, in the case of thin alumina layers, linear and nonlinear optical properties of the nanocomposites are enhanced, reaching values of -2.8 × 10−6 m/W and 1.6 × 10−13 m2/W for the third-order nonlinear absorption and refraction coefficients, respectively.

Ultrafast nonlinear refraction measurements of infrared transmitting materials in the mid-wave infrared.

We utilize the conventional Z-scan technique to provide absolute measurements of third-order nonlinear refraction coefficients (n2) in the mid-wave infrared at 2 µm and 3.9 µm of common optical materials that have transparency windows spanning this regime. We study a variety of narrow band gap and wide band gap semiconductors, fluoride crystals (BaF2, CaF2, LiF, and MgF2) and optical glasses, and a series of chalcogenide glasses. The n2 is found to span on the order of ∼10-15 to ∼10-12 cm2/W for the semiconductors, ∼10-16 cm2/W for the fluoride crystals and glasses, and ∼10-14 to ∼10-13 cm2/W for the chalcogenides. The experimental results are compared to previous measurements of n2 conducted in the visible and near-infrared along with empirical and theoretical formulations.

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.

Influence of strong light beams on the nonlinear refraction and absorption coefficients of transparent materials

We explore the effective nonlinear (NL) optical response of transparent materials illuminated by strong light beams. Two different setups were used to study the influence of the numerical aperture (NA) corresponding to the collecting lens on the measured coefficients in the open- and closed-aperture Z-scan transmittance. For that, we have reproduced experiments in ${{\rm CS}_2}$CS2 at 532 nm in the picosecond regime using the ${D}4\sigma$D4σ-Z-scan method. It is found that measurements of high-order NL coefficients are not possible after a limit defined by the self-focusing of light inside the cell, and that stimulated light scattering is not significant to explain alone the saturation behavior that occurs in the NL refraction measurements. Indications are given for future Z-scan-based experiments that may clarify the boundary conditions to be respected for the measurement.

Measurement of the nonlinear refractive index of Cs D1 line using z-scan

We present measurements of the nonlinear refraction coefficients for the D1 line of cesium vapor. A variant of the z-scan technique is applied for which we scan the laser frequency across resonance for different sample positions and detect the transmission after an aperture in the far field. From the spectra for different positions we reconstruct the position-dependent transmission z-scan curve for a given laser detuning. This technique allows obtaining the vapor Kerr coefficient over a large and continuous range of frequencies. From the saturation of the Kerr coefficient, n2, with beam power we obtain n4, the next term in the refraction index expansion. A theoretical model is used to calculate n2 and n4 giving values consistent with experimental ones.

Third-order optical nonlinearity of tungsten disulfide atomic layer with resonant excitation

The third-order optical nonlinearity of tungsten disulfide atomic layer was characterized with open and closed Z-scan techniques with a resonant excitation near an exciton absorption peak using a pulsed laser which has a temporal pulse width of ~6 ns and a Gaussian spatial beam profile. The normalized transmittance traces with open and closed Z-scan for the WS2 atomic layers displayed positive nonlinear absorption and negative nonlinear refraction. The nonlinear absorption and nonlinear refraction coefficients of WS2 with the resonant excitation were estimated to be ~6.0 × 10−8 m/W and ~-3.8 x 10−15 m2/W.

Performance modification of third-order optical nonlinearity of chalcogenide glasses by nanocrystallization

Abstract We demonstrate the modification of the third-order optical nonlinearity (TONL) of chalcogenide glasses (within the GeS2–In2S3–CsCl ternary system) by nanocrystallization, i.e., by controlling the precipitation of nanocrystals (in pure In2S3 phase) within the amorphous background. Compared with the parent glass, the resultant chalcogenide glass ceramics (ChGCs) have unchanged infrared transmittance but modifiable optical bandgap energy with treatment duration. Both nonlinear refraction coefficient and nonlinear absorption coefficient of the ChGCs are increased due to the appearance of In2S3 nanocrystals. ChGCs subjected to heat treatment for 1.3–2 h are found to exhibit the optimum TONL performance.

Synthesis, characterization, and nonlinear optical properties of some new series ofS-(5-aryl-1,3,4-oxadiazol-2-yl) 2-chloroethanethioate derivatives

In the present investigation, some novel S-(5-aryl-1,3,4-oxadiazol-2-yl)2-chloroethanethioate (3a-3e) derivatives were synthesized and their impact on optical properties was studied. They have also been characterized by elemental analysis and various spectroscopic methods including FTIR, $^{1}$H NMR, $^{13}$C NMR, and UV-Vis techniques. The nonlinear refractive indexes of 3a-3e were also measured in dichloromethane via Z-scan method using a continuous wave diode-pumped laser at 532 nm wavelength. The nonlinear refractive coefficient of compounds was obtained from ${10}^{11}\, \, {m}^{{2}}{/W}$ order. Regarding the appropriate nonlinearity of these compounds, they could be considered good candidates for biooptical and photonic applications. All the synthesized compounds (3a-3e) have also been evaluated for their antimicrobial and antifungal activities. The bioactive assay showed that the synthetic compounds displayed variable inhibition zones against tested bacterium Escherichia coli and fungus Aspergillus fumigatus in comparison to enrofloxacin and amphotericin as reference drugs, which are normally used for treating such infections.

Giant and Tunable Optical Nonlinearity in Single-Crystalline 2D Perovskites due to Excitonic and Plasma Effects.

Materials with large optical nonlinearity, especially in the visible spectral region, are in great demand for applications in all-optical information processing and quantum optics. 2D hybrid Ruddlesden-Popper-type halide perovskites (RPPs) with tunable ultraviolet-to-visible direct bandgaps exhibit large nonlinear optical responses due to the strong excitonic effects present in their multiple quantum wells. Using a microscopic Z-scan setup with femtosecond laser pulses tunable across the visible spectrum, it is demonstrated that single-crystalline lead halide RPP nanosheets possess unprecedentedly large nonlinear refraction and absorption coefficients near excitonic resonances. A room-temperature insulator (exciton)-metal (plasma) Mott transition is found to occur near the exciton resonance of the thinnest qunatum-well RPPs, boosting the nonlinear response. Owing to the rapidly changing refractive index near resonance, a single RPP crystal can exhibit different nonlinear functionalities across the excitation spectrum. The results suggest that RPPs are efficient nonlinear materials in the visible waveband, indicating their potential use in integrated nonlinear photonic applications such as optical modulation and switching.

Impurity related optical properties in tuned quantum dot/ring systems

ABSTRACTIn this paper, we explore the linear, third-order nonlinear, and total optical absorption coefficient (OAC) and refractive index change coefficient (RICC) of a GaAs doped quantum dot/quantum ring (QD/QR) with parabolic-inverse squared potential in conjunction with modified Gaussian confinement and taking into account the presence of on-centre shallow donor and or acceptor impurity. Calculations are done via the compact density matrix formalism and the iterative method. The two-dimensional parabolic QD/QR is subjected to uniform magnetic field oriented perpendicularly to the plane of the structure. The energy levels and wave function are derived within the framework of effective-mass and parabolic band approximation. The results exhibit that the OACs and RICC are clearly affected by different parameters of the applied confinement, strength of magnetic field, and the presence of impurity. The variation of confinement potential, nature of impurity, dot radius, cyclotron frequency of the parabolic confinement potential, and geometric parameter of the on-centre repulsive potential lead to either a red-shift or a blue-shift of the resonant peaks of the OACs and of the maximum and minimum of the RICC together with significant variations of the magnitudes of these resonant structures.

Nonlinear reverse saturation absorption, self-defocusing behavior and structure-property relationship of a novel 2,3,4-trimethoxy-4'-nitrochalcone single crystal

The present work describes the crystal structure, third-order nonlinear optical (NLO) properties and Hirshfeld Surface (HFs) analysis of 1-(4-nitrophenyl)-3-(2, 3, 4,-trimethoxyphenyl) prop-en-1-one (2, 3,4TMNC). The synthesized material was characterised by FT-IR, FT-Raman, UV–Visible, NMR [1H, 13C{1H}] and single crystal X-ray diffraction techniques. TGA-DTA analysis revealed that crystal has higher thermal stability. HFs analysis is performed to visualize intra and intermolecular interactions (C–H⋯O). The third-order NLO properties were studied using standard open and closed aperture Z-Scan technique with a continuous wave (CW) DPSS laser (λ = 532 nm). The calculated values of nonlinear refraction coefficient (n2), third-order nonlinear susceptibility (χ(3)) and nonlinear absorption coefficient (β) were found to be of the order of -10−9 cm2/W, 10−7 esu and 10−5 cmW−1 respectively. Normalized transmittance is decreased with increased input intensity of laser i.e. 2, 3, 4 TMNC showed good optical limiting property. The optical limiting threshold was found to be 3.36 kJ/cm2. Thus, the title chalcone derivative is a potential material for optical limiting applications.

Outstanding nonlinear optical properties of methylammonium- and Cs-PbX3 (X = Br, I, and Br–I) perovskites: Polycrystalline thin films and nanoparticles

Metal Halide Perovskites (MHPs) have arisen as promising materials to construct cost-effective photovoltaic and light emission devices. The study of nonlinear optical properties of MHPs is necessary to get similar success in nonlinear photonic devices, which is practically absent in the literature. The determination of the third order nonlinear coefficients is typically done by the Z-scan technique, which is limited by the scattering of polycrystalline thin films. In this work, we have studied nonlinear optical properties of polycrystalline CH3NH3PbX3 (MAPbX3) thin films and colloidal CsPbX3 nanoparticles with three different bandgaps (X3 = I3, Br3, and Br1.5I1.5). Their bright generation of photoluminescence under infrared illumination demonstrates an excellent efficiency of multiphoton absorption. The nonlinear absorption coefficient (β) was studied by analyzing the transmitted light through the samples, observing the expected Eg−3 dependence with values as high as β = 1500 cm/GW. In addition, we proposed the use of a modified Z-scan technique with imaging processing to analyze the nonlinear refraction coefficient (n2) under the laser damage threshold. Our experimental data agree quite well with theoretical predictions, demonstrating the accuracy of the method and potential applications to other thin films. Moreover, n2 parameter reaches values of 3.5 cm2/GW, indicating the suitability of MHPs for nonlinear photonics.

Linear and nonlinear optical properties of chlorophyll-a extracted from Andrographis paniculata leaves

This paper reports the linear and third-order nonlinear optical (NLO) properties of chlorophyll-a, a natural pigment extracted from the medicinal plant Andrographis paniculata. Silica column chromatography technique was used to extract the chlorophyll-a from the plant leaves. The functional groups present in the extracted sample were recognized by Fourier transform infrared (FT-IR) spectra. The sample was also characterized by UV–Vis, fluorescent spectra and Z–scan techniques. Z–scan study reveals that the extracted natural pigment chlorophyll-a evinces a large negative nonlinear refractive index n2 and nonlinear absorption coefficient β respectively owing to self-defocusing and saturable absorption behaviors. Third-order NLO susceptibility χ(3) of chlorophyll-a was measured to be of the order of 10–6 esu. The sample fulfilled the conditions for figure of merit and we believe that the natural pigments extracted from the Andrographis paniculata leaves may be suitable for all-optical switching applications.

Optical limiting properties of surface functionalized nanodiamonds probed by the Z-scan method

This work focuses on the optical limiting behavior of surface modified nanodiamonds (DNDs) namely, amino-terminated DNDs (DND-NH2) and hydrogen-terminated DNDs (DND-H). Their relevant nonlinear optical properties for optical limiting are compared to those of unfunctionalized DNDs. The optical limitation is characterized by means of nonlinear transmittance, Z-scan, and scattered intensity assessments when submitted to a nanosecond pulsed Nd:YAG laser operating at a wavelength of 532 nm. It is stated that the largest nonlinear attenuation is attributed to the DND-H system, whereas the exceedingly low threshold values for optical limiting for the DND-H and the DND-NH2 systems is attributed to their negative electron affinity character (NEA). Using Z-scan experiments, it is shown that nonlinear refraction combined with a significant nonlinear absorption predominates in the DND-H suspension, while the pure thermal origin of the nonlinear refractive index change is conjectured in the case of the DNDs. Besides, an amazing valley to peak profile was measured on DND - NH2indicating an unexpected positive sign of the nonlinear refraction coefficient. In addition, a stronger backscattered intensity signal is highlighted for the unfunctionalized DNDs through nonlinear scattering measurements.

Wavelength-dependent nonlinear optical properties of 8-(4-methoxyphenyl)-6-oxo-3-p-tolyl-6H-pyrido[1,2-b][1,2,4]triazine-7,9-dicarbonitrile

In this study, 8-(4-methoxyphenyl)-6-oxo-3-p-tolyl-6H-pyrido[1,2-b][1,2,4]triazine-7,9-dicarbonitrile (A) was prepared and then the nonlinear optical properties of this compound, including nonlinear refractive index (n2) and nonlinear absorption coefficient (β) were measured using Z-scan technique by continuous wave laser diode at wavelengths of 405 and 532 nm. At wavelength of 532 nm, by increasing the incident intensity a switch over from saturable absorption (SA) to reverse saturable absorption (RSA) was observed. The results showed that the nonlinear optical properties of this compound depend on the wavelength. It was also observed that with decreasing incident intensity, the thermal nonlinear refractive coefficient increased accordingly, while its thermo-optic coefficient decreased. In addition, the third-order susceptibility of this compound in wavelength of 532 nm was obtained higher than 405 nm.