Linear and nonlinear optical properties of dye-doped KDP crystals: Effect of thermal treatment

Potassium dihydrogen phosphate crystals (KDP, KH₂PO₄) doped with the organic xylenol orange (XO) dye are grown, the XO concentration in the crystal matrix is about 10 ppm. The spectral and luminescent properties of nominally pure, dye-doped and dye-doped/annealed at 150 °C crystals (KDP, KDP:XO and KDP:XO_an) were measured. The annealing temperature effect on the degree of dye protonation in the crystal matrix is established. Analysis of the IR-absorption spectra reveals a strong interaction between the incorporated dye molecules and the hydrogen subsystem of the matrix. The nonlinear optical (NLO) properties of KDP, KDP:XO and KDP:XO_an crystals are studied within the self-action effect of picosecond laser pulses at 532 nm. The mechanism of photoinduced bleaching and the effects of laser beam self-focusing (in KDP) and self-defocusing (in KDP:XO and KDP:XO_an) are supposed to be due to resonance excitation of the subsystems of intrinsic defects and dye molecules, correspondingly. For KDP:XO_an it is shown that thermal annealing of intrinsic crystal defects leads to domination of more effective NLO response of the subsystem of dye molecules that is correlated with photoluminescence data.     

l-Cystine hydrochloride: A novel semi-organic nonlinear optical material for optical devices

A new semi-organic nonlinear optical (NLO) material l-cystine hydrochloride (LCHCl) was grown in large size measuring 19 × 5 × 3 mm³ by slow solvent evaporation technique for the first time in literature. The cell parameter values were determined by single crystal X-ray diffraction studies. Fourier Transform Infrared spectroscopic analysis was carried out on the grown sample to ascertain the fundamental functional groups. Thermal behavior of the grown LCHCl sample was analyzed by TG & DTA analysis. The mechanical properties of the grown crystals have been studied using Vickers microhardness tester. The optical transmission studies and second harmonic generation (SHG) efficiency studies justified the device quality of the grown crystal and the SHG study reveals that the grown sample has nearly 1.2 times higher efficiency than that of potassium dihydrogen phosphate (KDP), a well known NLO material.     

Study of optical and thermal properties in nickel doped ZnS nanoparticles using surfactants

The presence of surfactants polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), sodium hexameta polyphosphate (SHMP) and tri-octyl phosphine oxide (TOPO) on the surface of Ni²⁺ doped ZnS (ZnS:Ni²⁺) nanoparticles resulted variation in their optical properties. The optical properties of each surfactant-capped ZnS:Ni²⁺ nanoparticles were investigated using UV–visible (UV–Vis) absorption and photoluminescence (PL) techniques. The absorption spectra and fluorescent emission spectra showed a significant blue shift compared to that of the bulk zinc sulfide. The effect of the optical properties in colloidal form (wet) and dry samples were investigated. Enhanced PL emission was observed for the dry samples at 80 °C. Thermal properties of the ZnS:Ni²⁺ was also studied using thermo gravimetric-differential thermal analysis (TG-DTA), Fourier transform infra-red spectrometer (FT-IR) and X-ray diffraction (XRD). The results are presented and discussed.     

Structural,electrical and optical properties of gamma irradiated methyl para-hydroxy benzoate single crystals

ABSTRACT

Nonlinear optical materials (NLO) have been garnering attention due to their role in optical data storage, optical communication and laser technology. Organic crystals have emerged as an extremely important class of NLO materials, since their NLO properties compare very well with traditional inorganic NLO materials like KCl, LiNbO₃, KDP (potassium dihydrogen phosphate), etc. They offer the additional advantage that they can be grown relatively inexpensively from solution close to room temperature, unlike the inorganic NLO materials which are grown from high temperature melts. In the present work, organic transparent single crystals of methyl para-hydroxy benzoate (MHB) were grown by slow evaporation solution growth technique (SEST) from aqueous solution at room temperature. The changes in structural, electrical and optical properties of gamma irradiated MHB single crystals were studied using X-ray diffraction (XRD), UV–Visible absorption spectroscopy, Photo-luminescence (PL), Fourier transform infrared (FTIR) spectroscopy and AC conductivity measurements at room temperature. The polished MHB single crystals were irradiated with gamma rays of doses 10 and 15 kilogray (kGy). From the XRD analysis, it was observed that gamma irradiation for these doses drastically decreases the crystallinity. The optical absorption constants were examined by UV-Visible absorption spectroscopy, measured over the wavelength range of 200–800?nm, at normal incidence. The optical band gap as estimated from the Tauc plot ((αhν)² vs hν) was found to be reduced with increasing gamma irradiation doses. PL spectra showed emission at wavelengths of 361?nm (3.43?eV) and 452?nm (2.74?eV), with enhanced intensities for the irradiated crystals. FTIR spectroscopy was utilised to identify the functional groups of MHB and indicated the rupture of specific types of bonds with gamma irradiation. Apart from that, the enhancement of AC conductivity with gamma irradiation was also observed for the gamma irradiated crystals.     

Structural,optical, spectroscopic and thermal investigations on novel semi-organic nonlinear optical material - Potassium boro-oxalate single crystal

In this work, a new semi-organic nonlinear optical material of Potassium boro-oxalate (KBO) is synthesized and subsequently a single crystal of size 7 × 5 × 3 mm³ is grown from the aqueous solution by slow evaporation technique at ambient temperature. Characterizations are performed on the single crystals to study the structural, thermal, linear and nonlinear optical (NLO) properties of the as-grown single crystals. Crystal and molecular structure of KBO are solved by direct method and further refinement is performed by full-matrix least-square method employing SHELXL-2014 software. Single crystal X-ray diffraction (SXRD) studies revealed that the grown crystal associates to triclinic crystal family with non-centrosymmetric space group P1. The Fourier transform infrared (FTIR) spectrum reflected the presence of various functional groups in the title compound. The Ultraviolet-visible-near infrared (UV-VIS-NIR) absorption and transmission spectrum are recorded to capture the suitability of the grown single crystals for various optical and NLO applications. The thermal decomposition and thermal stability of the KBO single crystals up to 187°C are investigated by TGA-DTG (Thermo Gravimetric - Differential Thermo Gravimetric), TGA-DTA (Thermo Gravimetric-Differential Thermal analysis) and DSC (Differential Scanning Calorimetry) curves. Kurtz-Perry powder technique is employed to explore the SHG (Second Harmonic Generation) efficiency of the KBO single crystals. SHG efficiency of KBO is found to be comparable to KDP.     

Studies on a novel organic NLO single crystal: L-asparaginium oxalate

A new organic nonlinear optical (NLO) material, L-asparaginium Oxalate (ASOX) was synthesized and single crystals of ASOX with dimension (10*5*5) mm³ was grown from aqueous solution by slow evaporation solution growth technique. Single crystal XRD data reveals that ASOX belongs to triclinic crystallographic system with non-centrosymmetric space group P1. The grown organic NLO crystal was subjected to various characterizations like PXRD, FT-IR analysis, thermal studies, micro hardness test and optical studies for identifying the transparency range and the emission spectrum. The laser damage threshold value was found to be 2.04 GW/cm². The second harmonic efficiency of the grown crystal was examined using Kurtz Perry powder technique and it was found to be 68% that of KDP. Hence it can be effectively employed for various optoelectronic and photonic applications.     

Structural, electronic and optical properties of pure and Ni-doped CdI2 layered crystals as explored by ab initio and crystal field calculations

Influence of impurity Ni²⁺ ions on optical absorption spectra of layered CdI₂ single crystals has been considered for localized level of doping. Optical properties of CdI₂:Ni²⁺ crystals were modeled using two independent approaches: (i) DFT-based ab initio calculations and (ii) semi-empirical crystal field theory. The former method allowed for locating the Ni²⁺ 3d states with respect to the host’s band structure, providing a link between the properties of impurity and host itself. The latter method allowed for calculations of crystal field splitting of the Ni²⁺ LS terms, giving an opportunity to assign the main bands in the absorption spectrum of the doped crystal. To increase accuracy in calculating the point charge contribution to the crystal field parameters (CFP), contributions of all crystal lattice ions located at a distance of up to 72.999 Å from the Ni ion were included into the crystal lattice sums. The crystal field Hamiltonian was diagonalized in the space of 25 wave functions of the spin-triplet terms ³F, ³P and the spin-singlet terms ¹S, ¹D, ¹G of the 3d⁸ electron configuration of Ni²⁺ ion. Additional calculations of the band structure and optical functions were performed to reveal the structure of the energy bands, their role in the formation of optical properties of this system in the overlapping impurity-ligand effects. Electron density distribution in the space between atoms before and after doping was compared; hybridization of the Ni 3d states with iodine 5p states was demonstrated. The role of the crystal anisotropy in the observed effects is discussed.     

Optical characterization of Mn, Ni and Co ions doped zinc lead borate glasses

This paper reports on the development and optical characterization of heavy metal oxide (HMO)-based transparent glasses in the chemical composition of 15PbO-40B₂O₃-(45−x) ZnO−x TM²⁺ (=Mn²⁺ or Ni²⁺ or Co²⁺) (where x=0.2, 0.5 mol%). For these glasses both absorption and emission spectra have been measured, in order to understand their optical performances. The XRD profiles have confirmed their glassy nature and the FTIR spectral features have been analyzed. From the emission spectra, a bright green emission (538 nm) from Mn²⁺-glasses, an intense red emission (670 nm) from Ni²⁺ and from Co²⁺ (625 nm) glasses have been noticed very clearly. Based on the UV-absorption spectra of these materials, both direct and indirect bond gaps have been computed. Apart from the spectral analysis, different physical properties of these glasses have also been carried out. Due to the presence of both PbO and ZnO, these glasses are found to be good moisture-resistant optical systems. Both optical and physical properties have been found to be more encouraging towards their use as novel luminescent optical materials.     

Configurational coordinate diagram of Ni2+ doped silver halide crystals,as determined by optical and luminescence measurements

Optical and luminescence measurements were carried out on Ni²⁺ doped silver halide crystals. The configurational coordinates of the ground and the first excited states made it possible to explain the important optical properties, such as the Stokes shift between the ground and excited states, the broadening of the bands with temperature and the thermal quenching. Determining the configurational coordinate diagram of the ground and first excited states is the first step for the design and fabrication of solid state and fiber lasers which are based on Ni²⁺ doped silver halides and which operate in the middle infrared.     

Optical properties of 3d-ions doped RbCdF3. Radiation effects

Abstract

The optical properties of RbCdF₃ crystals doped with Cr³⁺, Mn²⁺ and Ni²⁺ have been studied. Absorption and photoluminescence spectra correspond to these ions in an octahedral environment. The lifetimes of the emitting levels have been measured at different temperatures. Single exponential decays are obtained for Mn²⁺ and Ni²⁺ while a non-exponential decay is found in the case of Cr³⁺. Radiation effects have also been studied. A new absorption band is produced in the 305 nm region by RT X-irradiation. Exciting with light in this band the 3d-ions emissions are observed.     

Growth, optical, mechanical and dielectric studies on NLO active pure and metal ion doped single crystals of bis-thiourea zinc chloride

Good quality single crystals of pure and metal ion (Ni²⁺) doped bis-thiourea zinc chloride (BTZC) possessing excellent nonlinear optical properties have been grown from aqueous solution by the slow solvent evaporation technique. The lattice parameters of the grown crystals are determined by single crystal X-ray analysis. The well defined sharp peaks in the powder X-ray diffraction pattern reveals the crystalline perfection and the EDAX spectrum confirms the presence of dopant in the lattice of the parent crystal. The DRS UV-visible spectral study reveals improved transparency for the doped crystal, ascertaining the inclusion of metal ion in the lattice. The optical band gap of the pure and doped crystals was calculated to be 4.8 and 5.2 eV respectively from the UV transmission spectrum. The vickers hardness test brings forth higher hardness value for Ni²⁺doped BTZC as compared to pure BTZC crystal. The dielectric measurement exhibits very low dielectric constant and dielectric loss at higher frequencies for both the pure and Ni²⁺doped BTZC. The existence of second harmonic generation signals in the crystal also has been confirmed by performing the Kurtz powder test.     

Synthesis,crystal growth and characterization of novel semiorganic nonlinear optical crystal: Dichloro(beta-alanine)cadmium(II)

Semiorganic nonlinear optical material of dichloro(beta-alanine)cadmium(II) (DCBAC) have been synthesized and single crystals were grown by solvent evaporation method at room temperature. The lattice parameters of the grown crystals are determined by single crystal XRD. The modes of vibration of different molecular groups present in the sample were identified by the FTIR spectral analysis. Thermal stability of the crystal was investigated using thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The dielectric constants of the crystal were studied as a function of frequency and the results are discussed. The grown crystals are subjected to microhardness studies and the variation of the microhardness with the applied load is studied. The optical transmission spectra and second harmonic generation (SHG) were investigated to study its linear and nonlinear optical properties. The nonlinear optical (NLO) property of the crystal was confirmed by powder second harmonic generation (SHG) test. SHG efficiency is comparable to that of KDP.     

Synthesis,vibrational, thermal,mechanical and third-order nonlinear optical properties of sodium 4-methyl-3-nitrobenzoate monohydrate crystal for optical limiting applications✰

A nonlinear optical (NLO) sodium 4-methyl-3-nitrobenzoate monohydrate (Na4M3N) single crystal was synthesized and grown by the slow cooling solution growth method using an ethanol-water (1:1) mixed solvent. Powder X-ray diffraction (PXRD) reveals the crystallinity of Na4M3N compound. The Na4M3N crystal was estimated with a single crystal XRD instrument and it was identified to be in the centrosymmetric space group (P2₁/c) having a monoclinic system. The vibrational, proton (¹H) and carbon (¹³C) NMR spectral analysis substantiates the functional groups, hydrogen and carbons in the synthesized compound. The Hirshfeld surfaces analysis was executed to know the different type of interactions present in the crystal. From the UV–vis spectrum, the optical band gap and cut-off wavelength of the Na4M3N crystal are endowed to be 5.06 eV and 254 nm respectively. The Na4M3N crystal was subjected to a thermogravimetric as well as differential thermal analysis for discerning the thermal characteristics. The LDT value of crystal was endowed to be 5.8 GW/cm² using Nd: YAG laser and the value is superior to that of KDP and Urea. The emission region of the compound was identified by the photoluminescence emission spectrum. The crystalline quality was again confirmed by lifetime measurements. The thermo-optic coefficient (dn/dt) was determined to be –3.5 × 10⁻⁵ K⁻¹. The reverse saturable absorption observed by third-order NLO studies dictates the suitability for optical limiting applications. Vickers microhardness test showed that Na4M3N crystal was a soft material. The average etch pit density (3.2 × 10³ cm⁻²) was determined from chemical etching studies. The complex dielectric constant, electric modulus and electrical conductivity values were measured as a function of frequency to get information on the conduction mechanisms.     

Growth and design of novel nonlinear optical material (NLO) ⿿ Glycine barium nitrate potassium nitrate (GBNPN) crystal

A potentially useful semi organic nonlinear optical (NLO) material ? glycine with barium nitrate and potassium nitrate (GBNPN) has been synthesized by slow evaporation technique. Good transparent GBNPN crystals were obtained in a time span of 3 weeks. The grown crystals were characterized by single crystal/powder XRD, UV?vis?IR absorption, FTIR, thermal analysis and powder SHG measurements have been studied. The grown crystals were thermally stable up to 137.53 °C. The GBNPN crystal exhibits second harmonic generation efficiency of about 1.35 times than that of potassium di hydrogen phosphate (KDP). Mechanical properties such as micro hardness (H_v) and Mayer's index, n, have been carried out by indentation method. The refractive index (μ) has been measured by the Brewster's angle method.     

In situ evolution of Ni environment in magnesium aluminosilicate glasses and glass–ceramics–Influence of ZrO2 and TiO2 nucleating agents

The evolution of Ni²⁺ environment has been systematically investigated using optical and in situ X-ray absorption spectroscopy (XAS) to determine the influence of nucleating agents (TiO₂ and/or ZrO₂) during the formation of spinel in magnesium aluminosilicate glass–ceramics. The results were complemented by in situ X-ray diffraction data. According to XAS and optical spectroscopy, the nature of nucleating agents does not modify significantly the Ni environment in initial glasses. However, it has a relatively strong influence in the observed crystallization sequence. Ni²⁺ ions do not enter the Zr-containing crystalline phase of ZrO₂ or ZrTiO₄ but a Ni²⁺ coordination change from the fivefold coordinated sites, with a small amount of tetrahedral sites in parent glasses, to ^[6]Ni²⁺ and ^[4]Ni²⁺ sites in spinel (in glasses nucleated by ZrO₂ and/or TiO₂) or in β-quartz solid solutions (in glasses nucleated by ZrO₂) has been found.     

Studies on the electrical, linear and nonlinear optical properties of Manganese mercury thiocyanate bis-dimethyl sulfoxide, an efficient NLO crystal

Manganese mercury thiocyanate bis-dimethyl sulfoxide (MMTD), a novel organo-metallic nonlinear optical (NLO) crystal, was grown by a slow evaporation technique over a period of 30 days. The grown crystal was subjected to single crystal X-ray diffraction to determine the unit cell parameters. The optical properties of MMTD were investigated by UV-Vis-NIR, FTIR and FT-Raman spectroscopic techniques. The second harmonic generation (SHG) efficiency of the sample was measured using a Q-switched, mode-locked Nd:YAG laser and the results were compared with urea and manganese mercury thiocyanate (MMTC). The thermal parameters, such as the thermal diffusivity (α), thermal effusivity (e), thermal conductivity (k) and heat capacity (c_p) of MMTD were measured by the photopyroelectric (PPE) technique and the results are discussed. The dielectric response and mechanical properties of MMTD have also been investigated and reported.     

Spectral,thermal, optical and dielectric characterization of tris(tetraethylammonium) pentabromozincate(II) monohydrate crystals

Tris(tetraethylammonium) pentabromozincate(II) monohydrate, is a new semiorganic compound synthesized and crystallized by slow evaporation solution growth method at room temperature. The formation of the compound in the stoichiometric ratio was confirmed by elemental analysis. The crystalline nature of the compound was confirmed by powder X-ray diffraction method and the crystal system was found to be triclinic. The absorption spectrum of the compound shows absorption at 247 nm and it has wide transparency in the visible region. The lower cut-off wavelength and the optical transmittance window of the compound were identified by optical transmittance study. The thermogravimetric and differential thermal (TG–DTA) analyses were studied to find out the thermal stability of the synthesized compound. The thermal anomalies observed in the differential scanning calorimetry (DSC) analysis indicate that the compound shows a first order phase transition. The FTIR spectrum was used to characterize the various chemical bonds and water molecule present in the compound. The nonlinear optical property (NLO) of the material was analyzed by modified Kurtz–Perry powder technique and found that it has SHG efficiency three times greater than that of KDP. The dielectric constant and dielectric loss of the compound decrease with increase in frequency.     

Growth,linear and nonlinear optical studies on guanidinium 4-nitrobenzoate (GuNB): An organic NLO material

Single crystals of guanidinium 4-nitrobenzoate (GuNB) were grown using solvent evaporation technique by mixing aqueous solutions of guanidine carbonate and 4-nitrobenzoic acid at ambient temperature. X-ray diffraction analysis characterized the unit cell parameters of the grown crystal and the crystal belongs to monoclinic system. The optical properties of the grown crystal have been studied by means of transmission measurements in the wavelength region between 200 and 1200 nm. The optical constants such as refractive index (n) and extinction coefficient (k) have been determined from the transmittance data. The optical band gap (E_g), the real and imaginary parts of the dielectric constant of the grown crystal was determined. Second harmonic generation (SHG) efficiency of the grown crystal has been studied using Nd:YAG laser and was measured as 3.2 times that of KDP. The low dielectric constant suggests the suitability of this compound material for NLO applications.     

Growth, Characterization and Theoretical Study of a Novel Organometallic Nonlinear Optical Crystal: CdHg(SCN)4(C2H5NO)2

A novel potentially useful second harmonic generation (SHG) organometallic nonlinear optical (NLO) crystal: cadmium mercury thiocyanate bis(N-methylformamide), CdHg(SCN)₄(C₂H₅NO)₂ (CMTN), has been prepared, and large high-optical-quality single crystals with dimensions up to 30 ×27×9 mm³ have been grown by the temperature-lowering method. Its structural, physicochemical and optical properties are characterized by elemental analyses, X-ray powder diffraction, Fourier transform infrared and Raman spectroscopy, thermal analysis, powder SHG measurements and UV/Vis/NIR transmission. The specific heat has been determined to be 515.5 J?mol^?1?K^?1 at 300 K. CMTN possesses good physicochemical stability up to 128.5^°C, exhibits powder SHG efficiencies 0.8 times that of urea and its UV transparency cutoff is 358 nm. By the use of the DFT/B3LYP/6-31G(d) method, the microscopic second order NLO behavior of CMTN has been investigated by computing the first-order hyperpolarizability together with that of CdHg(SCN)₄ (CMTC) and CdHg(SCN)₄(C₃H₈O₂) (CMTG) crystals. The results have been explained based on their crystal structures.     

Growth and characterization of an efficient nonlinear optical single crystal: Urea p-nitrophenol

An organic nonlinear optical single crystal of urea p-nitrophenol has been synthesized and grown by slow evaporation solution growth technique. The grown crystals were characterized by single crystal and powder X-ray diffraction analysis and it was found to be the structure of the crystal belongs to triclinic system. The various functional groups were identified by FT-IR and Raman spectral analysis. Thermal stability of the grown crystal was studied by TGA/DTA. The optical properties of the grown crystals were analyzed by UV–vis. The mechanical properties of the grown crystal were studied by Vickers microhardness measurements. Nonlinear optical property of the crystal was confirmed using the Kurtz and Perry powder technique and a study of its SHG efficiency in comparison with KDP has made.