Nonlinear Refraction Behavior Research Articles

Hybrid Approach for Multiscale and Multimodal Time-Resolved Diagnosis of Ultrafast Processes in Materials via Tailored Synchronization of Laser and X-ray Sources at MHz Repetition Rates

The synchronization of laser and X-ray sources is essential for time-resolved measurements in the study of ultrafast processes, including photo-induced piezo-effects, shock wave generation, and phase transitions. On the one hand, optical diagnostics (by synchronization of two laser sources) provides information about changes in vibration frequencies, shock wave dynamics, and linear and nonlinear refractive index behavior. On the other hand, optical pump–X-ray probe diagnostics provide an opportunity to directly reveal lattice dynamics. To integrate two approaches into a unified whole, one needs to create a robust method for the synchronization of two systems with different repetition rates up to the MHz range. In this paper, we propose a universal approach utilizing a field-programmable gate array (FPGA) to achieve precise synchronization between different MHz sources such as various lasers and synchrotron X-ray sources. This synchronization method offers numerous advantages, such as high flexibility, fast response, and low jitter. Experimental results demonstrate the successful synchronization of two different MHz systems with a temporal resolution of 250 ps. This enables ultrafast measurements with a sub-nanosecond resolution, facilitating the uncovering of complex dynamics in ultrafast processes.

Superior optical limiting performance of lead-free metal halide perovskites nano-crystals embedded chalcogenide glass

The nonlinear optical properties of metal halide perovskites (MHP) are highly attractive, making them an emerging hotspot in the field of perovskite photonics. In this study, the third-order optical nonlinear properties of lead-free MHP (CsSnCl3) nano-crystals (NCs) embedded in a chalcogenide glass (GeS2-Sb2S3) substrate were characterized using the Z-scan technique. The spectral range examined was from 750 to 900 nm. Experimental results revealed that the incorporation of CsSnCl3 NCs enhanced the nonlinear refraction and nonlinear absorption behavior of the GeS2-Sb2S3 glass. Furthermore, the magnitude of these effects increased with the growth size of the CsSnCl3 NCs. Importantly, the MHP glasses exhibited strong two-photon absorption due to the large multiple-absorption cross-section of MHP crystals and the intrinsic high optical nonlinearity of the chalcogenide glass. The superior optical limiting performance induced by this process was successfully demonstrated.

Highly stable femtosecond pulse generation enabled by the indium tin oxide nanocrystals

The ultrafast third-order optical nonlinearity of indium tin oxide nanocrystals (ITO NCs) and their application in femtosecond laser generation have been investigated experimentally. The ITO NCs exhibit a large modulation depth of ∼25%, nonlinear refractive behavior with self-focusing, ultrafast carrier recovery time of ∼300 fs, and high damage threshold of ∼1.16 TW cm−2, and the stable femtosecond Er-doped fiber laser can be delivered with a signal-to-noise ratio over 80 dB modulated by the ITO NCs successfully. The experimental results indicate that the ITO NCs can be excellent ultrafast nonlinear optical materials for developing highly stable photonic and optoelectronic devices.

Ultrafast Dynamics and Strong Two-Photon Absorption Properties of Nonplanar β-Functionalized “Push–Pull” Copper Corroles with a Mixed Substituent Pattern

A new series of nonplanar and unsymmetrically β-functionalized "push-pull" copper corroles, CuTPC(CHO)R7 [R = H, Br, Ph, Me, or 2-thienyl (Th)], were synthesized and characterized to elucidate the effect of β-functionalization and nonplanarity on the photophysical, redox, and nonlinear optical (NLO) properties on the corrole ring. The synthetic route to unsymmetrically β-octasubstituted copper corroles includes bromination of CuTPC(CHO) to get CuTPC(CHO)Br7 in 80% yield, which was further subjected to the Pd-catalyzed Suzuki reaction. CuTPC(CHO)Br7 exhibited a large red shift in the Soret band (Δλmax = 35-40 nm) and both the Q bands (Δλmax = 10-50 nm), as compared to CuTPC and CuTPC(CHO). CuTPC(CHO)Br7 was 510 and 290 mV anodically shifted in the first oxidation and the first reduction compared to CuTPC owing to the strong -I effect of CHO and Br groups. Density functional theory studies revealed that all the β-octasubstituted copper corroles exhibited highly nonplanar saddle-shape conformation of the corrole ring. Very high torsional saddling was observed for CuTPC(CHO)Th7 (79-83°) than that for CuTPC (49-53°), even larger than that for CuTPCBr8 (67-70°). Femtosecond laser-induced third-order NLO studies from these copper corroles showed strong two-photon absorption cross-sections (0.48-6.98 × 104 GM) and self-focusing-type positive nonlinear refraction behavior. The observed structure-dependent two-photon absorption coefficients (β) are in the range of ∼2.7-20.9 × 10-12 m/W, and the n2 values are in the range of ∼0.64-6.45 × 10-18 m2/W. The present results may facilitate a new window for these copper corroles in nonlinear optical devices, femtosecond optical limiters, and many other ultrafast photonic applications.

Third order nonlinear optical absorption studies of Cr3+ doped PbWO4 nanostructures

We report the synthesis of Cr3+ doped PbWO4 nanoparticles with different concentration of Cr3+ through chemical method. The structural, morphological and optical characterization was studied through X-ray diffraction (XRD), Raman, UV–Visible spectra, Photoluminescence, X-ray photo electron spectroscopy (XPS) and Transmission electron Microscopy (HR-TEM). The XRD patterns revealed the tetragonal phase of stolzite and the peaks are highly crystalline structure with no segregation of Cr3+. UV–Vis absorption spectra reveal that the shift of absorption band edge towards higher wavelength upon doping of Cr3+ions. The average particle size of the nanostructure as revealed by the TEM image lies around 47 nm. Third order nonlinearity of Cr3+ doped PbWO4 nanoparticles were analysed by the standard Z-scan technique using 532 nm Nd: YAG laser. The observed nonlinear absorption (NLA) and nonlinear refraction (NLR) behavior is caused by thermal nonlinear effects due to localized heating. Experimental results have demonstrated that an increase in optical nonlinearity occurs with higher Cr3+ concentrations. Based on the observed nonlinearity it is suggested that the synthesized nanostructures could be used in various optical device applications.

Nonlinear characterization and optical switching of Acid red 27 dye

In this paper the linear and nonlinear optical properties(n2, β), also switching behavior of Acid Red 27 by Z-scan technique is used to study the nonlinear absorption and nonlinear refraction behavior of the organic dye Acid Red of laser at 532 nm with 5.26 mW, Where the value of the nonlinear absorption coefficient of the highest concentration 10-4 is 1.558*10-3(cm/W) and the value of the nonlinear refractive index was of the highest concentration 10-4 is 8.362*10-7 (cm2/W )and. The results show the behavior of Acid Red 27 is saturable also the dye have negative refractive index (self -defocusing)for all concentration studied according to the nonlinear results the behavior of optical switch have been studied by using laser at 532 nm as a pump and 632.8 nm as a prop, where it is observed that the amplitude of prop laser decreases with increasing modulation frequency. The effect of intensity and concentration on the number of diffraction rings was also studied, the results show the number of ring increased with increasing intensity of laser and concentration of dye.

Growth and optimization of optical traits of copper sulphate crystal exploiting L-ascorbic acid for photonic device applications

In current investigation organic ligand of L-ascorbic acid (LAA) has been firstly exploited to tune the optical properties of copper sulphate (CuS) single crystal. The pure and LAA influenced CuS crystal has been grown from aqueous solution by slow evaporation process. The powder X-ray diffraction technique has been employed to identify the crystal planes and evaluate the structural parameters of grown crystals. The functional groups of LAA influenced CuS (LAA-CuS) crystal has been recognized by Fourier transform infrared analysis. The impact of LAA on optical transmittance of CuS crystal has been examined within 200-900 nm by means of UV-visible spectral analysis. The Z-scan technique has been employed to examine the third order nonlinear optical (TONLO) properties of pure and LAA-CuS crystal. The eye-catching effect of LAA in switching the nonlinear refraction behavior of CuS crystal from self-focusing to self-defocusing has been explored. The magnitude of TONLO refractive index (n2), absorption coefficient (β) and susceptibility (χ3) of pristine and LAA-CuS crystal has been comparatively evaluated using the Z-scan transmittance data.

Effect of silver doping on ultrafast broadband nonlinear optical responses in polycrystalline Ag-doped InSe nanofilms at near-infrared.

There is great interest in transition metal-doped InSe because of its high nonlinearity and ultrafast response time at higher light fluence. Herein, Ag-doped InSe nanofilms were precisely manufactured using a direct current-radio frequency sputtering method, and their ultrafast broadband nonlinear optical responses in near-infrared were systematically researched. Ag-doped InSe nanofilm exhibited a broadband nonlinear optical response (800–1100 nm) and ultrafast carrier absorption (<1 ps), and can act as a potential semiconducting material for all-optical devices. Through precise control of the sputtering process parameters, Ag-doped InSe nanofilms were successfully prepared that were smooth, uniform, and exhibited no cracks. Nonlinear optical studies (femtosecond transient absorption spectroscopy and Z-scan measurement) indicated that nonlinear absorption behavior in Ag-doped InSe nanofilm withstands a transformation from saturation absorption to reverse saturation absorption arising from ground state bleaching, free-carrier absorption (FCA), and two-photon absorption (TPA). Additionally, nonlinear refraction behavior in Ag-doped InSe nanofilm was successfully detected near the intrinsic absorption edge, which arose from Kerr refraction and free-carrier refraction. More importantly, the broadband nonlinear response, ultrafast carrier absorption, and carrier recovery time of Ag-doped InSe nanofilm has the ability to controllably tune via Ag doping. Furthermore, Ag-doped InSe nanofilm possesses the nonlinear figure of merit (FOM) of 2.02, which indicates that Ag-doped InSe nanofilm is a promising semiconducting material for all-optical switching devices in near-infrared.

Thermally induced optical nonlinearity in colloidal alloy nanoparticles synthesized by laser ablation

Colloidal suspension of alloy nanoparticles has been prepared and their third-order nonlinear optical response was investigated by means of the Z-scan technique, employing 532 nm continuous wave laser excitation. Alloys colloidal suspension of industrial grade brass, aluminium, and copper was prepared via laser ablation in liquid technique. FESEM analysis reveals the particles size of less than 102.33 nm on average. The magnitude and sign of the nonlinear refraction, n2 and nonlinear absorption, β were determined. It was observed from the closed aperture Z-scan that all the suspensions exhibited a self-focusing effect with a negative nonlinear refractive index, n2, attributed to thermal lensing effect. Colloids of brass possess highest n2 followed by copper and aluminium suspension, attributed to the thermally agitated process whereby heat is transferred into non-local region of the propagation axis. Open Z-scan results revealed that the brass suspension exhibited saturable absorption (SA) with significant negative β value. Aluminium and copper alloy NPs suspension rather shows reverse saturable absorption with a positive β value. These materials were found to exhibit significant nonlinear refraction and nonlinear absorption behaviour, making them possible candidates for photonic and/or optoelectronic applications, especially with low powered continuous wave laser excitation.

Spectral and third order nonlinear optical properties of Yttrium-doped BaWO4 nanostructures

BaWO4 nanostructures doped with different concentrations of Yttrium have been synthesized by a chemical method. The as-prepared samples were characterized by UV–vis diffuse reflectance spectra, X-ray diffraction, Fourier transform infrared spectroscopy, Transmission electron microscopy and Raman spectra. From the UV–vis spectra, it is seen that absorption band edge shifted towards the visible region upon Y doping. The X-ray diffraction and Raman analyses reveal that the BaWO4 powders present a tetragonal structure. The third-order nonlinear optical responses of BaWO4 nanostructures on the effect of Y concentrations was investigated by Z-scan technique using a continuous wave Nd:YAG laser at 532 nm. Experimental results have shown that the observed nonlinear absorption and nonlinear refraction behavior is attributed to saturable absorption and thermal nonlinear effects.

Role of defect states on nonlinear properties of 8 MeV electrons irradiated zinc oxide thin films under off-resonant regime

In the present work, ZnO thin films were synthesized by sol-gel with subsequent spin coating on corning glass substrates. To understand the variations in the structural, optical, and nonlinear optical properties of ZnO thin films, 8 MeV electron irradiation with different dose rates (0 kGy, 1 kGy, 5 kGy, and 10 kGy) was performed. The XRD spectra showed transition from polar crystal growth orientation to non-polar crystal growth orientation of the films when the irradiation dose rate was increased from 0 kGy to 10 kGy and this was attributed to the reduced thickness of the irradiated films. The generation of localized surface states below the conduction band upon electron irradiation was confirmed by the quantification of the Urbach energy. A large band gap shrinkage was observed in the irradiated films (3.31–3.10 eV) due to the enhanced surface states. The photoluminescence spectra showed reduction in the NBE emission due to the enhanced surface states in the irradiated films. Open aperture and closed aperture Z-scan measurements were performed to extract the nonlinear absorption coefficient (β) and nonlinear refractive index (n2) values using 532 nm Nd:YAG laser having pulse width of 7 ns. The open aperture Z-scan profiles of the films showed the presence of normalized transmittance valley, which was attributed to the two photon absorption (TPA) behaviour. The reduction in the depth of the normalized transmittance valley in irradiated films was ascribed to the bleaching of carriers in the ground states due to their trapping in the defect states. The closed aperture Z-scan curves showed the presence of normalized pre-focal peak, followed by a valley, which is characteristic of the self-defocusing nonlinear refraction behaviour. The electron irradiation with different dose rates provided an opportunity to understand the variations in the optoelectronic properties of the ZnO thin films considering the various defect states generated upon irradiation.

Mid-infrared optical properties of chalcogenide glasses within tin-antimony-selenium ternary system.

In this work, we investigated the mid-infrared (MIR) optical properties of selenide (Se-based) chalcogenide glasses (ChGs) within an As- and Ge-free system, namely the environment-friendly and low-cost tin-antimony-selenium (Sn-Sb-Se, SSS) ternary system, which has not been systematically studied to the best of our knowledge. As compared to ChGs within those conventional Se-based systems, SSS ChGs were found to exhibit extended infrared transmittance range as well as larger linear refractive index (n0). Femtosecond Z-scan measurements show the presence of evident three-photon absorption from Urbach absorption of the SSS ChGs at MIR wavelength, which resonantly enhanced the nonlinear refractive behavior and resulted in large nonlinear refractive index (n2).

Study of all-optical switching properties of zinc phthalocyanine thin film by pump-probe technique

The nonlinear optical absorption, refraction and switching behavior of Zinc phthalocyanine (Zn(II)Pc) thin films are reported. Z-scan technique is employed to study the nonlinear absorption and nonlinear refraction behavior of the thin films with nanosecond pulses of Nd:YAG laser at ∼532nm. Optical switching behavior of the dye is studied using pump-probe technique with ∼5ns pulses of Nd:YAG at ∼532nm as the pump beam and ∼632.8nm cw He-Ne laser as the probe beam. The switching behavior of the dye is attributed to excited state absorption (ESA) of the probe beam by the dye molecules. Probe beam modulation with increasing pump intensity is also investigated.

Nonlinear Refraction Behaviour of Toluidine Blue O Dye-PVA Nanocomposite Films under CW Laser Light Excitation

Toluidine Blue O (TBO) dye-PVA nanocomposite films were prepared following a simple method based on solution-casting. Their morphology, linear as well as nonlinear optical properties were investigated. These nanocomposite films were characterized as nanoclustered aggregates grown within the PVA matrix. The nonlinear refraction behaviour of the nanocomposite films was investigated using Z-scan technique, under excitation with continuous wave (CW) laser light at 442nm for different peak incident intensities. The samples exhibited a negative nonlinearity and large nonlinear refractive index of the order of 10-6 cm2/W, which were better than some of the recently reported values for CW laser light excitation.

Synthesis and properties of benzothiadiazole-pyridine system: The modulation of optical feature

In this work, two new benzothiadiazole (BTD)-based compounds 1 and 2 were elaborately designed and synthesized, to explore the modulation on the interesting optical properties. Briefly, bipyridine-substituted compound 1 was synthesized via a modified Buchwald-Hartwig amination reaction with relatively high yield, and then derivative 2 was prepared by a following dehydrogenation reaction. The result in steady-state spectroscopic analysis and DFT/TDDFT calculation suggest the readily polarized nature of 1. In contrast, the readily polarized nature was declined in π-conjugated molecule 2, indicating the blue-shifted absorption and emission. Interestingly, negative cubic nonlinear refraction behavior in 1 is greater than that in π-conjugated system 2. Furthermore, in case 1 or 2, the photophycal property was considerably influenced by the external transition metal ion (M = Ag+, Cu2+ or Fe3+). Especially, because of the existence of external Fe3+ in case 1, initially negative nonlinear refraction signal became a positive one. Such exciting result is quietly useful for the design and synthesis of new functional BTD-based dye material.

Glass formation and mid-infrared optical nonlinearities of chalcogenide glasses in germanium-tin-sulfur ternary system

The glass forming region of chalcogenide glasses in a germanium-tin-sulfur (Ge-Sn-S) ternary system is depicted. Three series of Ge-Sn-S glasses in different compositions are selected and synthesized in order to investigate the dependence of structural, optical and third-order nonlinear properties on chemical composition. Spectroscopy analyses demonstrate that Ge and Sn have similar structural behavior in the glass network, while the introduction of Sn decreases the optical bandgap energy and improves the infrared transmittance of the glasses. Third-order nonlinear properties of the glasses are investigated by the Z-scan technique at a mid-infrared wavelength of 3.3 μm. The experimental results demonstrate that the nonlinear absorption at the mid-infrared wavelength is absent due to the large optical bandgap energy of the glasses, while the nonlinear refractive behavior is evident and can be improved by reducing number of [GeS4] tetrahedrons in the glass network.

Optical properties of Fe-doped BaTiO3 films deposited on quartz substrates by sol-gel method

Fe-doped BaTiO3 films were prepared on quartz substrates by sol-gel route. Linearly optical constants of the films were obtained by fitting transmittance spectra with Adachi’s model. With increasing Fe composition, refractive index n at 532 nm increases, single oscillator energy Ec and dispersion energy Ed increase, but optical band gap Eg decreases from 3.78 to 3.63 eV. In addition, nonlinear optical properties of the Fe-doped BaTiO3 films were analyzed by Z-scan method. Nonlinear optical responses of the BaTiO3 films were enhanced by Fe doping. For BaTi0.96Fe0.04O3 film, the third-order nonlinear refractive index coefficient γ, the nonlinear refractive index coefficient n2, the nonlinear absorption coefficient β and the third-order nonlinear susceptibility χ(3) are 1.98 × 10−13 m2/W, 1.03 × 10−6 esu, 1.33 × 10−7 m/W, 2.38 × 10−7 esu respectively. The nonlinearity is predominated by the nonlinear refractive behavior. These results suggest that Fe doping may tune the linear and nonlinear optical properties of BaTiO3 films, which indicates that Fe-doped BaTiO3 films are promising materials for applications in optical devices.

Investigation on fluorescence, third order non-linear optical and mechanical performance of glycine doped ADP crystal for applications of photonic devices

Optically transparent glycine doped ammonium dihydrogen phosphate crystals have been grown from aqueous solution by slow solution evaporation method. Crystallographic data of the grown crystal has been determined using the single crystal X-ray diffraction technique. The photoexcited colour centred fluorescence emission spectrum of the grown crystal has been analysed at an emission wavelength of 254 nm in the range of 300 to 700 nm. Z-scan studies have been performed at 632·8 nm to confirm the negative third order non-linear refraction behaviour of the grown crystal. The non-linear refractive index (n2), non-linear absorption coefficient (β) and third order non-linearity susceptibility (χ3) of the grown crystal were calculated using the Z-scan data to explore the material suitability for photonic applications. Vicker's microhardness test was carried out to analyse the mechanical stability and determine the hardness parameters of the grown crystal.

Synthesis, growth and optical studies of novel organometallic NLO crystal: Calcium bis-thiourea chloride

A novel organometallic crystal calcium bis-thiourea chloride (CBTC) has been synthesized and confirmed by means of EDX and FT-IR analysis. The (25×9×10)mm3 CBTC crystal has been grown from aqueous solution by slow solution evaporation technique. The UV–visible spectral study has been carried in the range of 200–900nm to assess the optical transparency of CBTC crystal. The optical constants such as band gap, optical conductivity, refractive index and reflectance of grown crystal have been evaluated using the transmittance data. The color centered fluorescence behavior of grown crystal has been explored in visible region. The Z-scan technique has been employed to determine the negative third order nonlinear refraction behavior of CBTC crystal. The magnitude of third order nonlinear refraction (n2), nonlinear susceptibility (χ3), nonlinear absorption (β) and FOM of grown crystal has been calculated using the Z-scan data. The χ3 of magnitude 3.56×10−5esu confirms the strong polarizing nature of CBTC crystal. The Kurtz-perry test confirmed the SHG efficiency of CBTC crystal is 1.15 times higher than KDP crystal material.

Low-threshold Optical limiting and Nonlinear refraction in Nanocomposite films of Light Green dye-polymer system

Poly(vinyl alcohol) (PVA) /Light Green (LG) dye nanocomposites were fabricated and their structure, microstructure, linear and nonlinear optical properties were investigated. The samples were characterized as nanocomposites with dye molecules encapsulated between the larger molecules (molecular chains) of the polymer host PVA. The nonlinear refraction behaviour was investigated employing the Z-scan technique, using a continuous wave (cw) He- Ne laser operating at 632.8 nm, as the excitation source. The samples displayed negative nonlinear refraction (self-defocusing) under the experimental conditions. Low-threshold optical limiting behaviour exhibited by the PVA based nanocomposites was demonstrated using an aperture limited geometry. The low limiting thresholds (~4 mW and ~2.4 mW) observed for the samples indicate that these low cost and durable nanocomposite films are potential media for optical limiting application under cw laser light excitation.