3rd-order Nonlinear Susceptibility Research Articles

Impact of Cd2+ substituted ZnAl2O4 spinel nanoparticles on structural, optical, morphological, magnetic and nonlinear optical behaviour

Cadmium-substituted ZnAl2O4 (CdxZn(1-x)Al2O4, where x = 0, 0.1, 0.3, and 0.5) nanoparticles were synthesized by the microwave combustion process. The XRD analysis confirmed the cubic system. The crystallite size of Cd2+ doped ZnAl2O4isin the range between 20.82 and 15.12 nm. Fourier transform infrared (FT-IR) spectra are displayed the stretching frequencies. The energy gap values decrease from 4.15 to 2.67 eV with increasing doping concentrations of Cd2+, which is due to the formation of sub-bands and is calculated by the Kubelka-Munk function. HR-SEM pictures showed the features of nanoclusters grain boundaries. The elemental mixing of Zn2+/Cd2+, Al3+andO2− was confirmed by EDX analysis. Magnetic properties reveal that the undoped ZnAl2O4 has diamagnetism and Cd2+ doped ZnAl2O4 system has superparamagnetic behaviour. The nonlinear index of refraction (10−8 cm2/W), nonlinear absorption coefficient (10−4 cm/W) and the 3rd order nonlinear susceptibility (10−6 esu) are found out by Z-scan experiments. The obtained results of optical limiting analysis confirm that these materials are viable candidates for devices like optical power limiters and optical switches.

Phase change, tuning of optical and dielectric parameters in Bi/S-Se-Sb heterostructure film upon thermal annealing: An experimental and computational approach

The study is based on annealing-induced Bi diffusion into Se30S30Sb40 sites that bring modification in its linear-nonlinear optical, structural, and dielectric properties. The Bi/Se30S30Sb40 heterostructure film was annealed at 100,150,200 and 250 °C. The Bi2Se3 and Sb2Se3 phase formation was confirmed from the X-ray diffraction as well as from the Raman study. The morphology has been studied by the field emission scanning electron microscopy images with increased particle size upon annealing. The uniformity and homogeneity of the film were noticed from the energy dispersive X-ray analysis elemental mapping. The bandgap decreased from 1.461 eV (as-prepared Bi/Se30S30Sb40) to 1.258 eV (250 °C annealed) with an increment in static refractive index from 2.864 to 3.114 which was noticed from the optical study. The linear optical parameters were tuned with annealing conditions and such changes were understood from the concept of density of states and defects in the film. The increase in dielectric loss factor and decrease in quality factor with annealing is accompanied by the increase in both electronic and optical conductivity. The plasma frequency decreased and optical electronegativity reduced from 1.728 (as-prepared Bi/Se30S30Sb40) to 1.692 (250 °C annealed) with annealing. The value of 3rd-order nonlinear susceptibility and non-linear refractive index gets almost doubled (i.e. 1.838 × 10−11 to 3.913 × 10−11 esu and 2.419 × 10−10 to 4.735 × 10−10 esu respectively) with annealing with an increase in the nonlinear absorption coefficient. The hydrophilic nature of the films with annealing was observed from the surface wettability study. The computational study by density functional theory provided the necessary idea for structural and physical parameters of the films.

Phase-change-driven tuning of linear and nonlinear optical properties of Te/As2Se3 bilayer thin films for optoelectronic applications

The present work reports the amorphous-crystalline phase transformation by interdiffusion of Te into the As2Se3 matrix with annealing at various temperatures (100, 150, and 200 °C). Te/As2Se3 bilayer thin films were prepared by electron beam evaporation under high vacuum conditions. The amorphous nature of As2Se3 thin film was confirmed from the X-ray diffraction study. The presence of small peaks in Te/As2Se3 thin film indicates the As4Te4 (monoclinic) and As2Se3 (monoclinic) phases, confirming the amorphous to crystalline phase transformation upon Te interdiffusion and subsequent annealing. The impact of Te top layer deposition on the vibrational modes were also observed from the Raman spectroscopy. The formation of Te agglomerates is confirmed from the morphological analysis which disappeared with further annealing. Furthermore, the water contact angle measurements have provided insight into surface interaction mechanisms of these materials. The linear and nonlinear optical properties were changed upon interdiffusion of Te as observed from UV–Visible spectroscopy. The increase in Eu indicated an increase in disorder hence the decrease in the bandgap. The 3rd order nonlinear susceptibility (χ3) and nonlinear refractive index (n2) increased with annealing. The tuning of linear and nonlinear optical properties by annealing can be used in various optoelectronic applications. Specifically, the phase transformation behaviour of Te/As2Se3 bilayer thin films enables their utilization in phase-change material-based optoelectronic devices.

An experimental and computational study for enhancement in optical nonlinearity and dielectric behaviour in thermal annealing induced Ag diffusion at Ag/Sb-S-Se interface

The annealing induced Ag diffusion into Sb40Se30S30 film brings enormous changes in its linear-nonlinear optical along with the structural and dielectric properties which is reported in the current study. The prepared Ag/Sb40Se30S30 film was annealed at different temperatures like 100,150,200 and 250 °C. The structure remained amorphous one as confirmed from XRD while the particle size increased with annealing as observed from FESEM images. The Raman study depicts the microstructural change in terms of shift in vibrational peaks. The optical study was done by UV–Vis-NIR spectrometer from which different optical parameters were evaluated. The decrease in optical bandgap with increase in linear refractive index is accompanied by the increase in optical density, extinction coefficient and decrease in skin depth. The dielectric loss factor increased while the quality factor decreased with annealing. The static dielectric constant increased with the increase in carrier concentration. Both the electrical as well as optical conductivity are found to be increased while optical electronegativity and plasma frequency decreased with annealing. The 3rdorder nonlinear susceptibility and non-linear refractive index are doubled with annealing while there is decrease in nonlinear absorption coefficient. The surface wettability study infers the hydrophilic nature sustains with annealing. The computational analysis using the DFT method was carried out to provide some necessary information about the structure and physical properties of the prepared materials.

Thermal annealing induced linear/nonlinear properties of Ag2S/As2Se3 heterojunction films for optoelectronic applications

The present study reports the annealing induced structural as well as optical properties of Ag2S/As2Se3 heterostructure film at different annealing temperatures. The trigonal AgAsSe2 phase formation was confirmed from the X-ray diffraction (XRD) and selective area electron diffraction (SAED) study. The bandgap of as-prepared Ag2S/As2Se3 film decreased on annealing. The reduction in bandgap increased the static refractive index with annealing. The Urbach energy increased from 422±3 meV to 464±2 meV whereas the optical density and extinction coefficient increased by annealing due to the formation of AgS–AsSe solid solution. The dispersion energy increased and consequently increased the oscillator wavelength and oscillator strength upon annealing. The carrier concentration and optical conductivity increased whereas the optical electronegativity decreased with annealing. The 3rd order nonlinear susceptibility (χ(3)) increased from 2.804x10−11 esu (as-prepared Ag2S/As2Se3) to 5.132 x10−11 esu upon annealing at 200 °C. The n2 value increased upon annealing which increased the nonlinear absorption coefficient but decreased the figure-of-merit. The contact angle value decreased (93°–47.6°) that shows the transformation of hydrophobicity to hydrophilic nature which is good for sensor applications like biological sensor. The surface roughness decreased upon annealing. The change in optical parameters upon annealing makes them the appropriate candidate for optoelectronics, dielectric and nonlinear optical applications such as memory devices, optical switch, etc.

Time dependent 532 nm laser irradiation on quaternary Sb10S15 In15Se60 films: An insight into its structural, morphological, and optical modifications for photonics application

The laser irradiation on films brings many changes in its different properties for optoelectronic applications. The current work deals with the deposition of Sb10S15In15Se60 film by thermal evaporation technique and then laser irradiated at different time durations to study the variation in structural and optical properties. In the present investigation, laser irradiation was carried out by 532 nm laser (2.33 eV) for different time durations, such as 0, 10, 20, 30, and 60 min. Due to the irradiation process, the surface morphology changed while the structure remained polycrystalline in nature by increase in crystallinity with irradiation time. All the optical parameters (linear and nonlinear) were calculated from UV–Vis spectroscopy data. Due to irradiation, the transmission decreased and shift in absorption edge occurred that leads to the reduction in optical gap from 1.73 eV to 1.27 eV. Such photodarkening phenomenon increased the refractive index which led to the increase in nonlinear optical entities like nonlinear refractive index and 3rd order nonlinear susceptibility. The variation of carrier concentration, VELF, and SELF, were also evaluated at different exposure times. The observed changes in the structural and optical properties with laser irradiation are suitable for various photonics devices.

Influence of time dependent laser-irradiation for tuning the linear-nonlinear optical response of quaternary Ag10In15S15Se60 films for optoelectronic applications.

The impact of laser irradiation on thin films results in multiple beneficial modifications of their structural, morphological, nonlinear-linear properties for optoelectronics applications. This work deals with the thermally evaporated Ag10In15S15Se60 films and post-laser irradiation to study the variations in structural and optical properties. The current investigation was carried out for different laser irradiation time durations such as 0, 10, 20, 30, and 60 minutes by 532 nm laser (2.34 eV). According to the X-ray diffraction analysis, all thin films have polycrystalline character. The change in the surface morphology after being exposed to the laser has been checked by FESEM, whereas the presence of constitutional elements has been verified by the EDX study. The related changes with laser irradiation in the optical properties, including both linear and nonlinear, were studied using UV-Vis spectroscopy data. The irradiation caused an enhancement in the transmission, and the absorption edge moved towards a lower wavelength, increasing the bandgap energy from 1.71 eV to 1.88 eV. The refractive index reduced as a result of the film's altered structure. The behaviour of the refractive index satisfies Moss's rule (E g n 4 = const). The nonlinear refractive index, first-order and 3rd order nonlinear susceptibility, is found to be decreased with laser irradiation. The dielectric parameters are also observed to be decreased with irradiation. Considering all the alterations in its properties caused by irradiation, the Ag10In15S15Se60 sample could be a favourable material for various photonic devices.

Enhancement of nonlinear optical parameters upon phase transition in new quaternary Ge20Ag10Te10Se60 films by annealing at various temperatures for optoelectronic applications

The current work investigates the influence of annealing at different temperatures on new quaternary Ge20Ag10Te10Se60 films. The phase transition from amorphous to crystalline with annealing is being studied from XRD and supported by TEM analysis. The Raman study shows the change in microstructural changes in terms of vibrational modes. The particle size increased with annealing along with the growth of Ag2Te, AgTe3, GeSe2, Ag2Se phases. The compositional and morphological study is carried out by EDX analysis and FESEM study. The linear optical properties of the material have been calculated from the UV-Visible spectra. The decrease in the optical bandgap of the films upon annealing is due to phase transition and increase in the surface dangling bonds. The static refractive index and the nonlinear refractive index are found to be increased with annealing. The significant increase in 3rd order nonlinear susceptibility with annealing is useful for nonlinear optical applications. The high-frequency dielectric constant increased upon annealing. The structural and optical changes are explained on the basis of amorphous to crystalline transformation and density of defect states. Increased value of nonlinear refractive index with decreased optical electronegativity with annealing is useful for nonlinear and optoelectronic applications.

Synthesis, characterization, and DFT study of linear and non-linear optical properties of some novel thieno[2,3-b]thiophene azo dye derivatives

Some novel thieno[2,3-b]thiophene-2,5-dicarbonitrile derivatives namely; 3,4-bis(2-hydroxynaphthalen-1-yl)diazenyl)thieno[2,3-b]thiophene-2,5-dicarbonitrile, 3,4-bis(4-aminonaphthalen-1-yl)diazenyl)thieno[2,3-b]thiophene-2,5-dicarbonitrile and 3,4-bis(4-(dimethylamino)phenyl) diazenyl)thieno[2,3-b]thiophene-2,5-dicarbonitrile have been synthesized and characterized by FT-IR and NMR spectroscopies.Thin films of the synthesized thieno[2,3-b]thiophene-2,5-dicarbonitrile derivatives have been deposited by the thermal evaporation method and characterized by UV-VIS-NIR spectroscopy. Their spectral dependences of absorption, dielectric, dispersion and allied parameters have been investigated, discussed, and compared with published results. The high absorption coefficient (∼105cm−1) at a solar maximum wavelength (λ≅500nm) and the band and optical gap energies of 2.95 and 2.15 eV, respectively manifested by the present samples make them suitable to be applied in optoelectronic devices, especially as solar absorber material. The revealed high values of non-linear refractive index n2 and 3rd order non-linear susceptibility revealed by these organic compound films, which are significantly higher than those of chalcogenide and oxide materials recommend them as promising NLO-elements. These results have been insured by geometry optimization and NLO calculations using Density Functional Theory with B3LYP method in the level of 6–311 G (d,p).

Modulation of the optoelectronic properties of polyimide (Kapton-H) films by gamma irradiation for laser attenuation and flexible space structures

polyimide (PI or Kapton-H) has proven its potential in the field of optoelectronic, nuclear technology and space industry due to its excellent electric insulation, transparency and flexibility. The present study focuses the effect of γ-irradiation (0, 25, 50 and 100 Mrd) on the structural, optical, AC electrical conductivity and dielectric properties of PI film samples. In the results, the crystallite size was shown to be increased from 37.77 to 73.42 Å in the X-ray diffraction XRD study. Certain variations in assignment bands like (O–H) stretching and carbonyl (CO) symmetric stretching were observed in FTIR spectrum. A shift in the absorption edge is observed in the UV–vis spectroscopy to higher wavelengths and consequently a decrease in both direct and indirect band gap energy Egopt. The calculated values of the refractive index n is also increased upon γ-irradiation. The parameters of Wemple - DiDomenico (WDD) are calculated for pristine and γ-irradiated film samples. The dependence of the dissipation factor tanδ and optical conductivity σopt are studied as a function of the photon energy (hν) at different γ-doses. Moreover, the 3rd order non-linear susceptibility χ(3) and non-linear index of refraction n2 were also studied. Optical limiting measurements indicate that irradiation of PI samples with high γ-dose (100 Mrd) highly attenuated the laser beams (532 and 632.8 nm) which may be useful for use in optoelectronic laser limiters and filters. The AC electrical conductivity σac, dielectric constant ε′ and dielectric loss ε″ are also investigated in the range of frequency (100 Hz - 1 MHz). The values of σAC are enhanced by irradiation with γ-rays and the behaviors of the frequency exponent s indicates that the AC conduction in PI samples is governed by the correlated barrier hopping (CBH) mechanism.

Increase in nonlinear susceptibility and refractive index in quaternary In15Sb10S15Se60 thin films upon annealing at different temperature for photonic applications

The current paper reports the thermal annealing induced amorphous to crystalline transformation of the quaternary In15Sb10S15Se60 thin films prepared by the thermal evaporation method on glass substrate. The prepared films were annealed at 100 °C, 150 °C, 200 °C, and 250 °C under vacuum conditions. The structural characterization was done by X-ray diffraction and Raman spectroscopy which revealed the amorphous to crystalline transformation and the formation of different phases for the annealed films. The composition of the films was verified by Energy dispersive X-ray analysis, whereas the surface morphology pictures were taken by field emission scanning electron microscopy and atomic force microscope. The changes in both linear and nonlinear optical properties of as-prepared and annealed films were studied from UV-Vis spectroscopy data and related empirical formula. The significant reduction in transmission (55–4%) and shifting of absorption edge due to annealing resulted in the decrease of optical bandgap (from 1.641 eV to 1.301 eV) and increase in linear refractive index. The 3rd order nonlinear susceptibility (9.83 ×10−15 to 2.44 ×10−11 esu) and nonlinear refractive index (4.59 ×10−13 to 6.01 ×10−10 esu) were found to be increased due to more polarization effect. The role of annealing temperatures on the variation of different parameters was elaborately explained on the basis of amorphous to crystalline transition and defect states in the localized region. Based on the observed changes in the linear and nonlinear optical parameters by thermal annealing, the In15Sb10S15Se60 thin films could be a suitable candidate for numerous photonic and optoelectronic applications.

Enhancing the third-order nonlinearity and crystallinity by selenium incorporation in tin sulfide films (SnS1−xSex) for optoelectronic applications

The effect of Se doping in SnS alloys which decreased the transmission and increase in crystallinity of the films with change in morphology. The optical bandgap decreased and there was a simultaneous increase in 3rd order non-linear susceptibility.

Facile synthesis of Cu2O nanoparticles using pulsed laser ablation method for optoelectronic applications

Cu2O nanoparticles were synthesized by pulsed laser ablation (Nd:YAG laser, 7 ns, and 1064 nm) of Cu plate immersed in liquid media from ultra-pure water, and its particle sizes were varied by changing the repetition rates between pulses to be useful for optoelectronic applications. The prepared colloidal suspension nanoparticles were characterized based on different physical process as the diffraction of X-ray laser beam, the electronic transition of UV–visible light source, or plasma emission from laser-matter interaction by the techniques of X-ray diffraction, UV–visible spectroscopy, and laser-induced breakdown spectroscopy, respectively. These techniques showed decreasing in the average particle sizes as increasing in the repetition rate of a pulsed laser. After that, the optical nonlinearity of the prepared samples was investigated by the Z-scan technique to inform the nonlinear parameters as 2nd order nonlinear absorption coefficient (β), 3rd order nonlinear susceptibility (X3), and the nonlinear reflective index (n2), optical limiting property and its proposed mechanism. The prepared nanostructured materials of Cu2O materials have a good optical limiter material with a limiting threshold value around 0.7 GW/cm2 and a damage threshold around 1.4 GW/cm2. These results confirmed that the saturable absorption process was carried by two-photon absorption, especially when the repetition rate of the used pulsed laser during the laser ablation process.

An impact of novel Terbium (Tb) doping on key opto-nonlinear optical characteristics of spray pyrolyzed NiO nanostructured films for opto-nonlinear applications

This work reports an impact of novel Terbium (Tb) doping on physical characteristics of NiO nanostructured films. The doping concentrations of Tb varied from 0 to 5.0 wt% in NiO system and are characterized using various characterization techniques. Thin films show the cubic structure preferred orientation along (111). Sizes of crystallites of films increases with Tb doping contents and strain of the films decreases. Optical constants (such as energy gap, absorption and refractive indices) are examined as a function of Tb doping concentrations. Optical band gap showed a blue shift with Tb doping concentrations. In addition, 3rd order nonlinear susceptibility and refractive index have been noticed in range of 1.78 × 10−14 -6.71 × 10−11 esu and 7.62 × 10−12 - 5.81 × 10−10 esu; respectively. Room temperature photoluminescence spectra of films reveal band-to-band transitions in UV region. Above opto-nonlinear investigation of Tb:NiO nanostructured thin films reinforce the potential candidate for optoelectronics applications.

In situ laser irradiation: the kinetics of the changes in the nonlinear/linear optical parameters of As50Se40Sb10 thin films for photonic applications.

The photosensitivity of amorphous chalcogenide thin films brings out light-induced changes in the nonlinear and linear optical parameters upon sub-bandgap and bandgap laser irradiation. The present work reports the in situ laser irradiated changes in the optical properties of As50Se40Sb10 thin films. The thermally evaporated film showed an exponential decrease in optical bandgap and increase in Urbach energy. The decay rate of the bandgap was 6.24 min and growth rate of Urbach energy was 6.67 min respectively. The dynamics of photo-induced changes were observed from the changes in linear refractive index and its dependent parameters such as 3rd order nonlinear susceptibility, nonlinear refractive index, dispersion and dielectric parameters. The conversion of heteropolar to homopolar bonds induced the photodarkening mechanism that changed the dispersion parameters. The decrease in Ed and Eo reduced the oscillator strength along with the zero-frequency dielectric constant. The optical and electrical conductivity changed significantly with time. The changes were saturated with time which brings stability in the film properties that is useful for various optical applications. However, no structural and compositional changes upon laser irradiation were noticed from the X-ray diffraction and EDX studies respectively. The surface homogeneity was checked from the FESEM picture.

Extraction of higher-order nonlinear electronic response in solids using high harmonic generation

Nonlinear susceptibilities are key to ultrafast lightwave driven optoelectronics, allowing petahertz scaling manipulation of the signal. Recent experiments retrieved a 3rd order nonlinear susceptibility by comparing the nonlinear response induced by a strong laser field to a linear response induced by the otherwise identical weak field. The highly nonlinear nature of high harmonic generation (HHG) has the potential to extract even higher order nonlinear susceptibility terms. However, up till now, such characterization has been elusive due to a lack of direct correspondence between high harmonics and nonlinear susceptibilities. Here, we demonstrate a regime where such correspondence can be clearly made, extracting nonlinear susceptibilities (7th, 9th, and 11th) from sapphire of the same order as the measured high harmonics. The extracted high order susceptibilities show angular-resolved periodicities arising from variation in the band structure with crystal orientation. Our results open a door to multi-channel signal processing, controlled by laser polarization.

Nonresonant Nonlinearity of Silver Nanoparticles

Results of experimental investigations of the process of nonlinear refraction in composite materials based on silver nanoparticles in the region far from the plasma surface resonance of the nanoparticles (λ = 1064 nm) are presented. The reflection Z-scanning technique was used for measurements, which made it possible to determine both the sign and the values of nonlinear refractive indices and real parts of the 3rd-order nonlinear susceptibility of composite materials. The mechanism responsible for the process of nonlinear refraction in specimens is discussed.

New Possibilities of Optically Heterodyned Polarization Interferometry of Isotropic Media: Linearly and Circularly Polarized Pump and Probe Waves

We present consistent theoretical studies of the optically heterodyned polarization interferometry (OHPI) with collinear circularly and linearly polarized interacting beams in the framework of the 3rd-order nonlinear susceptibility. A new method for measuring the phase of the nondegenerate susceptibility that is based on the dependence on the pump beam intensity in the standard OHPI scheme is proposed. The conditions for observing the signals which are purely due to linear or circular light-induced dichroism and birefringence are discussed and new experimental arrangements are suggested. Further, the optimum sample length to detect the OHPI signal is derived. The line shape of the OHPI signal and the elimination of the broad background in nonlinear polarization spectrposcopy are also discussed.

Conception of Normal Waves in Nonlinear Polarization Spectroscopy

A theoretical study is presented of normal waves in media with nonlinear photoanisotropy (light-induced anisotropy) within the framework of the 3rd-order nonlinear susceptibility tensor. In the general case, it is shown that the normal waves are elliptically polarized. These two ellipses have the same shape and opposite directions of rotation, and their major axes are not at right angles to one another. Expressions are derived for the ellipticities and the angle of the nonorthogonality of the normal waves. Several applications of theoretical results are given to demonstrate the relevance of the conception of normal waves in nonlinear spectroscopy. We show that the media with light-induced anisotropy acquire the anisotropic properties of crystals and can be applied to a wide range of laser devices due to optically controlled parameters.

Nonlinear Polarization Spectroscopy with Nonpolarized Light

A new variant of nonlinear polarization spectroscopy that is based on the use of nonpolarized pump (or) and probe beam is presented. We show that in the case of a totally depolarized strong exciting field, an initially isotropic medium acquires the properties of uniaxial absorbing crystal with optical axis along a wave normal of the pump beam. Relationship for a transverse component of the 3rd-order nonlinear susceptibility tensor is derived for arbitrary directions of interacting beams. When a probe beam is totally depolarized, a medium with light-induced anisotropy (MLIA) can be used as a light-absorbing or light-amplifying dynamic polarizer. We analyze the efficiency of such type of light controlled devices on the basis of the polarization nearness. The Mueller matrix of MLIA is calculated and some advantages of the use of partially polarized probe beam are pointed out.