arXiv subjects

I. V. Kityk

Publications and source records attributed to I. V. Kityk.

13 recordsLinked to original sources

arXiv2022

Optoelectronic and nonlinear optical properties of Lu doped AgGaGe3Se8 crystallites

A complex studies of optoelectronics, non-linear optical and laser stimulated piezoelectric features of chalcogenide powder-like chalcogenide crystals pure and rare earth doped AgGaGe3 Se8 crystallites are presented. It is shown principal role of the morphology for the titled materials. The contribution to nonlinear optical, photoconductivity and laser stimulated piezoelectricity are comparable. The temperature dependences are explored. The possibilityity to operate by the features of the titled crystallites in the optically reflected regime is shown. This may be important for laser operated triggers, modulators, photo detectors etc. The relaxation processes are studied. Among the NLO features main attention is devoted to second harmonic generation efficiencies in the reflected regime where principal role is played by morphology. Additionally the laser stimulated piezoelectric for the near the surface states with different morphology of grains is explored. It is demonstrated that contribution of the near-the surface states for such kind of effects will be commensurable to the bulk-like contribution.

physics.app-ph↗

arXiv2020

Formation of nano-size Cr layers on LiNbO$_3$ crystal surfaces by dissimilar electric charges

Morphology of metal thin layers deposited on polished surfaces of LiNbO$_3$ crystal with dissimilar electric charges has been studied using various methods of vacuum evaporation. The principal goal of the work is to optimizemethods of thin metal coating deposition applied to polar surfaces of LiNbO$_3$ crystal. The conducted research has demonstrated that Cr deposition on LiNbO$_3$ crystal faces is characterized by dissimilar polarity results in growth difference conditions of Cr films. The principal role here is played by the sign of the electric charge on the crystal surface along with the type (thermal or magnetron) and conditions observed during sputtering (deposition rate, substrate temperature etc).

cond-mat.mtrl-sci↗

arXiv2020

Second and third harmonic nonlinear optical process in spray pyrolysed Mg:ZnO thin films

In the present study, Mg-doped ZnO (MZO) nanofilms (NF) were grown by spray pyrolysis technique. X-ray diffraction (XRD) patterns have shown an intense peak oriented along (002) crystalline plane confirming crystalline origin of grown MZO films. Atomic force microscopy (AFM) data revealed that the average roughness decreased significantly upon Mg doping from 20.3 nm to 4.72 nm. Ambient temperature photoluminescence spectra accounted for four emission bands in the visible spectral region due to the presence of various intrinsic defect centres in the films. The non-linear absorption coefficient beta_eff were estimated by open aperture Z-scan technique and found to be in the order of 10-2 (cm/W) and indicates a positive absorption nonlinearity. Additionally, it was observed that incorporation of the metal Mg ions leads to a decay of the second harmonic generation (SHG) and to a non-regular increase of the third harmonic generation (THG).

cond-mat.mtrl-sci↗

arXiv2020

Strategic improvement of second and third harmonic generation in multifunctional Cu-Sn-S3 ternary semiconducting thin films

We propose a low-cost approach for the synthesis of multifunctional CuSnS3 (CTS) ternary compound thin film via spray pyrolysis technique. By varying Sn and S doping concentrations, a high energy absorber layers of CuSnS3 thin films were deposited on a glass substrate at a substrate temperature of 405 C. The prepared samples were analysed with respect to their optical, structural and electrical and nonlinear optical properties. X-Ray diffraction (XRD) analysis reveals that the films exhibit a tetragonal crystal structure with a preferential growth orientation along (1 1 2). The surface morphology of the films was explored by atomic force microscopy (AFM) in tapping mode configuration. Variation in the carrier charge density and electrical properties were observed for different Sn and S combination. The analysis of the Raman spectra indicates the presence of multiple phases apart from CuSnS3. The obtained Raman spectra were assigned to phonon mode as per zone centre phonon representation of optical and acoustic modes and identified to dominant A symmetry modes. The maximal laser stimulated induced second harmonic generation (SHG) signal was observed for the CTS 3 film and the corresponding second order nonlinear optical susceptibility which was equal to about 0.89 pm/V at 1064 nm and the minimal SHG signal was found for the CTS 2 film (about 0.22 pm/V). This strategic improvement in SHG and third harmonic generation (THG) signal efficiency endorses the role of Sn and S in modulating second and third harmonic generations in CuSnS3 compound.

cond-mat.mtrl-sci↗

arXiv2020

Laser stimulated second and third harmonic optical effects in F: SnO2 nanostructures grown via chemical synthetic route

Laser stimulated second and third harmonic generation effects in Fluorine doped tin oxide (F:SnO2) nanostructures versus the fluorine content is presented. The F:SnO2 nanostructures have been fabricated at various fluorine doping concentrations by spray pyrolysis technique. The films exhibit polycrystalline nature with a preferential growth orientation along (1 1 0) diffraction plane as evident from x-ray diffraction studies. The optical transmittance of the F:SnO2 films has increased from 68 percent to 80 percent. Photoluminescence studies revealed that strong violet emission peak corresponds to 400 nm and relatively weak red emission peak at about 675 nm was observed for all the F:SnO2 films. Increase in the\b{eta}eff value upon fluorine incorporation supports the applicability of the deposited films in passive optical limiting applications. The principal origin of second harmonic generation signals (SHG) for this type of nanostructures is played by the space charge density acentricity due to the F doping. The enhanced second and third harmonic generation signals observed on F:SnO2 nanostructures endorses the credibility of these materials in various nonlinear optical trigger device applications.

physics.app-ph↗

arXiv2020

Methodical engineering of defects in Mn$_x$Zn$_{1-x}$ O($x$ = 0.03, and 0.05) nanostructures by electron beam for nonlinear optical applications: A new insight

A series of MnxZn1-xO (x=0.03, 0.05) nanostructures have been grown via the solution based chemical spray pyrolysis technique. Electron beam induced modifications on structural, linear and nonlinear optical and surface morphological properties have been studied and elaborated. GXRD (glancing angle X-ray diffraction) patterns show sharp diffraction peaks matching with the hexagonal wurtzite structure of ZnO thin films. The upsurge in ebeam dosage resulted in the shifting of XRD peaks (101) and (002) towards lower angle side, and increase in FWHM value. Gaussian deconvolution on PL spectra reveals the quenching of defect centers, implying the role of electron beam irradiation regulating luminescence and defect centers in the nanostructures. Irradiation induced spatial confinement and phonon localization effects have been observed in the films via micro Raman studies. The later are evident from spectral peak shifts and broadening. Detailed investigations on the effect of electron beam irradiation on third order nonlinear optical properties under continuous and pulsed mode of laser operation regimes are deliberated. Third order absorptive nonlinearity of the nanostructures evaluated using the open aperture Z-scan technique in both continuous and pulsed laser regimes shows strong nonlinear absorption coefficient \b{eta} eff of the order 10-4 cm/W confirming their suitability for passive optical limiting applications under intense radiation environments. Laser induced third harmonic generation (LITHG) experiment results supports the significant variation in nonlinearities upon electron beam irradiation, and the effect can be utilized for frequency conversion mechanisms in high power laser sources and UV light emitters.

physics.app-ph↗

arXiv2020

Effect of Na doping on photoluminescence and laser stimulated nonlinear T optical features of ZnO nanostructures

In this work, nonlinear optical properties of Na: ZnO thin films (Na: ZnO) have been experimentally elaborated. The principal possibility to operate the nonlinear optical features using external laser beams is shown. The Na: ZnO films were synthesized by spray pyrolysis technique at a deposition temperature equal to about 400 C. XRD graph reveals that the grown films were polycrystalline in nature with a dominant peak corresponding to (0 0 2) plane. Despite the difference in the ionic radii of the Na and Zn, an angle shift in the XRD peak was not observed, whereas there was a significant change in peak intensity. The photoluminescence (PL) spectra resulted in three emission centres spectrally situated in violet, blue and green colour region due to the presence of native defect states in the forbidden energy gap. Second and third harmonic generation (SHG, THG) ex-periments stimulated by external coherent light beams show the existence of THG maxima for 15% Na doped Zn:O which was quite different with respect to SHG maximum for pure ZnO. The main innovation of this work is the possibility to change nonlinear optical susceptibility varying Na doping concentration and by coherent laser treatment, contrary to the previous works where these parameters have not been explored.

physics.app-ph↗

arXiv2019

X-ray photoelectron spectroscopy, Raman and photoluminescence studies on formation of defects in Cu:ZnO thin films and its role in non-linear optical features

The structural, optical, morphological and nonlinear optical properties of Cu:ZnO spray-coated films are studied. The surface morphology of Cu:ZnO thin films turned out to be homogenous, crack free and well covered with pea-shaped grains. The peak shift observed in the x-ray photoelectron spectroscopy spectra of the Cu:ZnO thin films infers the defect states present in the films. The satellite peak observed at 939.9 eV for Cu2P core-level spectra confirms the +2 oxidation state of Cu in the films. The formation of additional defect levels in the nanostruc-tures upon Cu doping was investigated using photoluminescence (PL) and Raman spectroscopy studies. The luminescent centers in the violet, blue and green spectral region were observed. The most prominent emission was centered at the blue color center for 5% Cu:ZnO thin films. The en-hancement in the PL emission intensity confirms the increase in the defect state density upon Cu doping. The shifting of the UV emission peak to the visible region validates the increase in the non-radiative recombination process in the films upon doping. The phonon modes observed in Raman analysis around 439, 333 and 558 cm-1 confirm the improvement in the crystallinity and formation of defect states in the films. X-ray diffraction reveals that the deposited films are of single-phase wurtzite ZnO structure with preferential growth orientation parallel (0 0 2) to the C-axis. The third-order optical susceptibility \c{hi}(3) has been increased from 3.5 x 10-4 to 2.77 x 10-3 esu due to the enhancement of electronic transition to different defect levels formed in the films and through local heating effects arising due to continuous wave laser illumination. The enhanced third harmonic generation signal investigated using a Nd:YAG laser at 1064 nm and 8 ns pulse width shows the credibility of Cu:ZnO films in frequency tripling applications.

cond-mat.mtrl-sci↗

arXiv2018

Some aspects of measuring nonlinear optical features of advanced vertically aligned mesoporous silica thin films activated by silver and copper ions

Described experimental conditions, reproducibility and optimization for the nonlinear optical effects (SHG, THG) for the diagnostic of functionalization of vertically aligned mesoporous silica thin films activated by silver and copper ions. The samples synthesis procedure are described in details. The dependence sof the seonc dhamroni genriaotn (SHG) and third harmonic genriaotn (THG) verus the fundamental energy density are presetned. The diffences between the SHG and THG energy power dependences are observed.

physics.optics↗

arXiv2013

Specific features of band structure and optical anisotropy of Cu2CdGeSe4 quaternary compounds

The complex theoretical and experimental studies of the band structure and the optical functions of the Cu2CdGeSe4 quaternary crystals are reported. The benchmark band structure calculations were performed using the first-principles methods. As a result, the structural, electronic, optical and elastic properties of Cu2CdGeSe4 were calculated in the general gradient approximation (GGA) and local density approximation (LDA). The calculated dielectric function and optical absorption spectra exhibit some anisotropic behavior. Detailed analysis of the band energy dispersion and the effective space charge density helped in establishing the origin of the band structure anisotropy. All calculated properties are compared with the experimental data. An additional comparison with a similar crystal of Cu2CdGeSe4 allowed to reveal the role played by the anions (S or Se) in formation of the optical properties of these two materials.

cond-mat.mtrl-sci↗

arXiv2013

Photoinduced features of energy band gap in quaternary Cu2CdGeS4 crystals

Quaternary chalcogenide crystal Cu2CdGeS4 was studied both experimentally and theoretically in the present paper. Investigations of polarized fundamental absorption spectra demonstrated a high sensitivity to external light illumination. The photoinduced changes were studied using the cw 532 nm green laser with energy density about 0.4 J/cm2. The spectral maximum of the photoinduced anisotropy was observed at spectral energies equal to about 1.4 eV (energy gap equal to about 1.85 eV) corresponding to maximal density of the intrinsic defect levels. Spectroscopic measurements were performed for polarized and un-polarized photoinducing laser light to separate contribution of the intrinsic defect states from the pure states of the valence and conduction bands. To understand the origin of the observed photoinduced absorption near the fundamental edge, the benchmark first-principles calculations of the structural, electronic, optical and elastic properties of Cu2CdGeS4 were performed in the general gradient approximation (GGA) and local density approximation (LDA) approaches. The calculated dielectric function and optical absorption spectra exhibit some anisotropic behavior within the 0.15...0.20 eV energy range near the absorption edge; the optical anisotropy was also found in the deep inter-band transition spectral range. Peculiar features of chemical bonds in Cu2CdGeS4 were revealed by studying the electron density distribution. Possible intrinsic defects are shown to affect considerably the optical absorption spectra. Pressure effects on the structural and electronic properties were modeled by optimizing the crystal structure and calculating all relevant properties at elevated hydrostatic pressure. The first estimations of the bulk modulus (69 GPa (GGA) or 91 GPa (LDA)) and its pressure derivative for Cu2CdGeS4 are reported.

cond-mat.mtrl-sci↗

arXiv2013

Z-scan analysis and ab initio studies of beta-BaTeMo2O9 single crystal

The Z-scan measurements for the non-centrosymmetric optical crystals β-BaTeMo2O9 (BTMO) were performed. The corresponding experiments were carried out using the 5 ns pulses of the second harmonic of a nanosecond Nd:YAG laser at the 532 nm wavelength. It was shown that the studied crystals possess promising third-order optical susceptibilities, which allow to use the crystal as optical limiters. The comparison with other oxide materials is presented. To clarify the origin of the observed effect, the electronic and optical properties of BTMO were calculated using the density functional theory (DFT)-based method. The performed calculations of the electronic and optical properties revealed certain peculiar features that can be suitable for the non-linear optical applications. The relation between the observed nonlinear optical features and the calculated band structure is emphasized. The values of the calculated band gap and refractive index for β-BaTeMo2O9 are also reported.

cond-mat.mtrl-sci↗

arXiv2008

Optical second harmonic generation in Yttrium Aluminum Borate single crystals (theoretical simulation and experiment)

Experimental measurements of the second order susceptibilities for the second harmonic generation are reported for YAl3(BO3)4 (YAB) single crystals for the two principal tensor components xyz and yyy. First principles calculation of the linear and nonlinear optical susceptibilities for Yttrium Aluminum Borate YAl3(BO3)4 (YAB) crystal have been carried out within a framework of the full-potential linear augmented plane wave (FP-LAPW) method. Our calculations show a large anisotropy of the linear and nonlinear optical susceptibilities. The observed dependences of the second order susceptibilities for the static frequency limit and for the frequency may be a consequence of different contribution of electron-phonon interactions. The imaginary parts of the second order SHG susceptibility chi_{123}^{(2)}(omega), chi_{112}^{(2)}(omega), chi_{222}^{(2)}(omega), and chi_{213}^{(2)}(omega) are evaluated. We find that the 2(omega) inter-band and intra-band contributions to the real and imaginary parts of chi_{ijk}^{(2)}ł(omega) show opposite signs. The calculated second order susceptibilities are in reasonably good agreement with the experimental measurements.

cond-mat.mtrl-sci↗