Order Nonlinear Optical Coefficients Research Articles

Consequences of dielectric mismatch on linear and third order nonlinear optical properties for CdS/ZnSe core/shell QD-matrix

In this work, we have performed a detailed investigation on optical properties for CdS/ZnSe spherical core/shell quantum dots surrounded by various dielectric matrices such as PVA, PMMA and SiO2. The wave functions and eigenenergies of confined electrons have been theoretically computed using the effective-mass formalism and the density matrix approach. The linear and third-order nonlinear optical properties have been evaluated for different matrices. Our results demonstrated that the linear, third order nonlinear optical absorption coefficients and refractive index changes are considerably sensitive to the geometrical parameters, the incident optical intensity and the dielectric environment.

Optical behaviour of nematic liquid crystal doped with carbon dot in the nonlinear optical regime

We delve into the effect of carbon dot (c-dot) doping at different concentrations (0.1, 0.2, 0.4, and 1 wt%) on the third order nonlinear optical properties of a nematic liquid crystal (NLC). C-dots were synthesized by the thermal decomposition of ammonium citrate salt. The size and morphology of prepared c-dots were confirmed by the TEM micrograph. Nonlinear optical properties of c-dot doped liquid crystal were investigated by the z-scan method using a Q-switched Nd: YAG laser delivering 7 ns pulse at 532 nm wavelength. A phenomenal increase in the nonlinear absorption coefficient, βeff, was observed for 0.2 wt% c-dot doped liquid crystal. There is an enhancement in the value of third order susceptibility, χ(3), of the order of 10 for the doped liquid crystal. An increase in the third order nonlinear optical absorption coefficient implies a better optical limiting characteristic than the pristine LC. The optical limiting threshold value of 0.2 wt% c-dot doped LC is found to be 1.23 J/cm2. We determine for the first time that c-dot doping in NLC leads to a significant improvement of the nonlinear optical properties compared to pure LC. The results indicate that the system under study could be a promising candidate for nonlinear photonic devices and optical limiters.

Solvent polarity sensitive characteristics of various tautomers of azo compounds: Linear and nonlinear optical properties.

Solvents as complex environments can induce considerable effects on the physical, chemical and biological properties of solute molecules. In this work, solvent polarity sensitive characteristics of two tautomers of different azo compounds were studied by using of spectroscopic and Z-scan techniques. In this case, nature and various molecular interactions contribution on the spectral behaviors of azo and hydrazone forms of selected samples were investigated by Kamlet-Abboud-Taft and Catalan models. Moreover, the obtained results of Z-scan indicate that self-defocusing, saturable and reverse saturable absorption features of azo dyes depend highly on substituents and molecular environment polarity characteristic. In this case, media polarity properties have the same effects on the third order nonlinear absorption coefficient and nonlinear refractive index values. Therefore, by measuring one of the third order nonlinear optical coefficients, it is possible to predict solvent polarity effects on the other nonlinear optical coefficient. The calculated dipole moments with high values in the molecular excited state also reveal the probability of molecular charge transfer characteristics. In this case, by excitation process, sample I indicate high dipole moment values in comparison to other samples. Therefore, the results can give useful information about the application of selected samples for designing various optical devices.

A series of novel BODIPY-fluorene copolymers: Synthesis, characterization, optical-electronic and nonlinear optical properties.

A series of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) with different connection sites and conjugation length and fluorene alternating conjugated polymers have been synthesized via palladium-catalyzed Suzuki coupling reaction. The polymers were fully characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC), and their properties were measured by thermogravimetric analysis (TGA), UV-vis absorption spectroscopy, cyclic voltammetry (CV), photoluminescence (PL) spectroscopy, the Z-scan technique, and theoretical calculation using density-functional theory (DFT) method. The results indicate that the connection sites and conjugation length of BODIPY have great effect on the optical-electronic and nonlinear optical properties of the conjugated BODIPY- fluorene copolymers although they don't affect the polymerization process. The absorption and emission peaks of P1 exhibit red shifts compared to those of P2 and P3. The polymers show good nonlinear optical properties that are closely related to the connection sites of the BODIPY pendants. P1 exhibits relatively richer nonlinear optical (NLO) properties than P2 and P3. The third order nonlinear optical coefficient (χ(3)) of P1 is 3.57 × 10-11 esu, which is ~4 times larger than those of P2 and P3.

Studies on growth and characterization of (E)-N′-[4-(dimethylamino) benzylidene]-4-hydroxybenzohydrazide hemihydrate: a nonlinear optical material

Hydrazone compound (E)-N′-[4-(dimethylamino) benzylidene]-4-hydroxybenzohydrazide hemihydrate (DMABHBH) was synthesized and single crystals of DMABHBH were grown by solvent evaporation method at room temperature. Molecular structure of DMABHBH compound was confirmed by 1H and 13C nuclear magnetic resonance techniques. The presence of functional groups was confirmed by Fourier transform infrared and FT Raman spectral analyses. The X-ray crystal structure was elucidated at 173 K by single crystal X-ray diffraction and the results were compared with the corresponding values obtained at 298 K. The compound crystallizes in the chiral monoclinic space group P21. Mechanical stability of the grown crystals was estimated from the Vicker’s microhardness test. Powder second harmonic generation efficiency of DMABHBH is about 1.1 times that of potassium dihydrogen phosphate. DMABHBH is found to show optical limiting behavior at high input light intensities, the third order nonlinear optical absorption coefficient measured using open aperture Z-scan studies, is 0.95 × 10−11 m/W. Anti-bacterial activity was studied using the well and disc diffusion methods.

Laser damage threshold, hardness and third order non-linear optical analysis of potassium dihydrogen phosphate with sodium chloride

Abstract z-scan technique was used to investigate the non-linear optical properties of Potassium dihydrogen phosphate doping sodium chloride (PDPSC) were grown slow evaporation solution growth technique at room temperature. The lattice parameters were calculated from single x-ray diffraction. Laser damage threshold value was found to be 13.48 GW/cm2. The Vickers microhardness test was carried out on the grown crystals and there by Vickers hardness number (Hv), work hardening coefficient (n), yield strength (σy), stiffness constant C11 were calculated. The z-scan technique has been employed to determine the third order nonlinear optical (TONLO) nature of PDPSC crystal at 532 nm. The third order nonlinear optical linear absorption coefficient (α), Nonlinear refractive index (n2), Nonlinear absorption coefficient (β), Real part of the third-order susceptibility [Re (χ|3|)], Imaginary part of the third-order susceptibility [Im (χ|3|)] and Third-order nonlinear optical susceptibility (χ3) has been calculated using the Z-scan data.

The effect of different doses of γ –ray irradiation on the third order nonlinear optical properties, molecular structure and mass attenuation coefficients of synthesized colloidal silver nanoparticles

Silver nanoparticles (Ag NPs) stable colloid solution were prepared via Creighton method and successively irradiated with gamma rays from a 60Co source at integral doses of 20 Gy, 200 Gy, 1 kGy and 10 kGy.The size of obtained nanoparticles was determined by field emission scanning electron microscopy (FESEM) is about 30 nm. The structure of synthesized Ag NPs was characterized by UV–Vis spectroscopy and X-ray diffraction (XRD) techniques. A wide absorption band centered at 400 nm can be distinctly observed by UV–Vis spectroscopy. Bragg reflections in X-ray diffraction analysis confirmed the presence of face-centered cubic (fcc) Ag NPs.The third-order nonlinear optical properties, molecular structure and mass attenuation coefficients of nano colloidal silver were studied before and after γ-ray irradiation. Prepared Ag NPs exhibit strong third-order nonlinear optical responses, which have been performed with a Z-scan technique using continues wave (CW) He: Ne laser emitting 632.8 nm. Comparing nonlinear results show that the magnitude of nonlinearity enhanced by increasing the dose of γ -ray irradiation. Raman signals of the obtained Ag NPs are significantly enhanced after the γ-irradiation process. Also, the experimental results using gamma spectroscopy method have shown that the mass attenuation coefficients of Ag NPs decrease after gamma irradiation. Briefly, results demonstrated that γ-ray irradiation is an effective method for tailoring the properties of Ag NPs.

Ultrafast carrier dynamics and third order nonlinear optical properties of aluminum doped zinc oxide (AZO) thin films

Aluminum doped zinc oxide (AZO) thin films were fabricated by simultaneous RF/DC magnetron sputtering technique on sapphire (Al2O3) substrate with different DC sputtering power 2, 6, 8 and 10 W respectively. The sputtered thin films were annealed at 350 °C in order to improve the crystal quality. AZO thin films are systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-VIS spectrometer for structural and optical properties. XRD patterns show that all sputtered thin films are well crystallized with hexagonal wurtzite structure. SEM images reveal the average crystallite sizes are increased after doping Al in ZnO which agreed with the calculated values from XRD. All thin films possess high optical transmittance in visible region and optical band gap values are relatively increased with Al concentration. The ultrafast transient absorption (TA) of AZO was analyzed by femtosecond pump-probe spectroscopy. The kinetic TA curves were fitted by tri-exponential decay function and obtained decay time constants are found to be in few picosecond and nanosecond range for ultrafast and slow processes respectively. Third order nonlinear optical absorption and refraction coefficients were investigated by using Z-scan technique. The observed nonlinear coefficients are enhanced with Al concentration in ZnO.

Influence of bis-thiourea nickel nitrate on the structural, optical, electrical, thermal and mechanical behavior of a KDP single crystal for NLO applications

A single crystal of bis-thiourea nickel nitrate (BTNN) doped potassium dihydrogen phosphate (KDP) has been grown from solution at room temperature by a slow evaporation technique. The cell parameters of the grown crystals were determined using single crystal x-ray diffraction analysis. The different functional groups of the grown crystal were confirmed using Fourier transform infrared analysis. The improved optical parameters of the grown crystal have been evaluated in the range of 200–900 nm using UV–visible spectral analysis. The grown crystal was transparent in the entire visible region and the band gap value was found to be 4.96 eV. The influence of BTNN on the third order nonlinear optical properties of KDP crystal has been investigated by means of the Z-scan technique. The second harmonic generation (SHG) efficiency of grown crystal measured using a Nd-YAG laser is 1.98 times higher than that of pure KDP. The third order nonlinear optical susceptibility (χ3) and nonlinear absorption coefficient (β) of BTNN doped KDP crystal is found to be 1.77 × 10−5 esu and 5.57 × 10−6 cm W−1 respectively. The laser damage threshold (LDT) energy for the grown crystal has been measured by using a Q-switched Nd:YAG laser source. The bis-thiourea nickel nitrate shows authoritative impact on the dielectric properties of doped crystal. The influence of bis-thiourea nickel nitrate on the mechanical behavior of KDP crystal has been investigated using Vickers microhardness intender. The thermal behavior of BTNN doped KDP crystal has been analyzed by TGA/DTA analysis.

Facile preparation of crosslinkable organic EO polymers based on AZO nonlinear optical chromophore: great indemnification for long term of stability

Due to the simple preparation technology and appropriate crosslinking process, polyurethane was selected as the host polymer for the preparation of organic electro-optics (EO) materials. The synthesis and crosslinking process of polyurethane demanded the nonlinear optical (NLO) chromophore possessing strong stability in acid environment. Fortunately, after the introduction of azo group in the electronic bridge, the stability of this kind of chromophores in acidic environment was improved greatly. Polyurethane EO polymers and EO films based on this kind of chromophore were prepared successfully. The crosslinking process was monitored by infrared spectroscopy clearly. The crosslinking process has direct relationship with the molecular weight of the crosslinkers. Crosslinker of triethanolamine with small molecular weight showed low crosslinking temperature (80 °C) and short crosslinking time (20 min). The crosslinking temperature and time was improved to 140 °C and 60 min based on Poly(bisphenol A glycidyl ether aniline) (BPAN) crosslinker with large molecular weight. More importantly, this kind of EO polymers showed us large second order nonlinear optical coefficients (76.1 pm/V) and good long term stability (130 °C).

Optical absorption in a disk-shaped quantum dot in the presence of an impurity

The linear and third order nonlinear optical absorption coefficients have been calculated in a two dimensional disk quantum dot. The confinement potential has been taken to be a combination of a parabolic and inverse squared part. The study has been performed in the presence of a perpendicular static magnetic field and a central or off-central impurity. The resulting Schrödinger equation has been solved by applying the variational method. It has been found that the presence of impurity causes a huge increase in the square of the transition matrix and in the absorption coefficients, in particular in the third order coefficient. Moreover, the asymmetry which results in the case of off-central impurity has been dealt with carefully by taking into consideration the transition matrices which vanish in other cases.

Femtosecond third order optical nonlinearity and optical limiting studies of (γ and β)—Barium borate nanostructures

Single phase (γ and β) barium borate with nanorod structures were prepared by hydrothermal method at reaction conditions of 433 and 1073K, respectively. FESEM images demonstrated the transformation of nanoclusters into elongated nanorods as the reaction time increased. The third order nonlinear optical (NLO) properties of the samples were investigated by the Z-scan technique (800nm, 150fs, 100MHz). Both phases of barium borate depicted nonlinear absorption and was assigned to the two-photon absorption mechanism. γ–BBO demonstrated negative nonlinear refraction (self-defocusing) while β-BBO showed positive nonlinear refraction (self-focusing). Both the phases exhibited optical limiting behavior and the limiting threshold was found to be in the order of μJ/cm2. Nanorods possessed superior third order NLO coefficients compared to nanoclusters of barium borate. Also γ–BBO possessed superior NLO properties compared to β–BBO and it can be strongly emphasized that γ–BBO nanorods can be used as a potential material for photonic applications.

A study on the properties of potassium pentaborate crystals

Potassium pentaborate (KB5) single crystals were grown by slow evaporation solution growth method and the properties of the grown crystals were investigated. Single crystal and powder X-ray diffraction studies were carried out to determine the crystal structure and lattice parameters of the grown crystals. The optical transmittance of the crystal was ascertained by recording UV–vis–NIR spectrum. Vibrational modes were assigned using FT-IR and FT-Raman spectra. Vickers hardness test estimates the mechanical properties for various loads. Thermal properties were investigated using TGA/DTA and DSC analysis. Second Harmonic Generation (SHG) was confirmed by Kurtz–Perry technique. Third order nonlinear optical properties nonlinear absorption coefficient, nonlinear refractive index and third order nonlinear susceptibility was calculated by Z-scan method using 632.8nm He–Ne laser.

Structural, linear and nonlinear optical study of zinc tetra-tert-butyl phthalocyanine thin film

Zinc tetra-tert-butyl phthalocyanine (ZnTTBPc) thin films were deposited on cleaned glass substrates by thermal evaporation technique. The ZnTTBPc films undergo phase transformation from unstable amporphous into stable crystalline form when annealed at 473K as evidenced from the X-ray diffraction study. The UV–vis absorption spectral study revealed an increase in the optical band gap from 3.03eV for amorphous α-phase to 3.12eV for the crystalline β-phase of the film. The AFM topographic images display a significant change in the surface morphology of film due to thermal annealing. Nonlinear optical studies of stable β-phase were performed with picosecond (ps) laser pulses operating at a wavelength of 800nm. The present work is, the first such attempt to measure the third order nonlinear optical (NLO) coefficients of thermally evaporated β-phase ZnTTBPc thin films using ps laser pulses. The strong nonlinear absorption (NLA) and nonlinear refraction (NLR) coefficients (β and n2) i.e. 2×10−7cm/W and −7×10−11cm2/W, respectively, indicates thermally evaporated ZnTTBPc films could be a promising material for nonlinear optical device applications.

The effects of pressure and hydrogenic donor impurity on the linear and nonlinear optical properties of a GaAs/GaAlAs nanowire superlattice

The combined effects of hydrostatic pressure, presence and absence of hydrogenic donor impurity are investigated on the linear and nonlinear optical absorption coefficients and refractive index changes of a GaAs/Ga1−xAlxAs nanowire superlattice. The wave functions and corresponding eigenvalues are calculated using finite difference method in the framework of effective mass approximation. Analytical expressions for the linear and third order nonlinear optical absorption coefficients and refractive index changes are obtained by means of compact-density matrix formalism. The linear and third order nonlinear absorption coefficient and refractive index changes are presented as a function of photon energy for different values of hydrostatic pressure, incident photon intensity and relaxation time in the presence and absence of hydrogenic donor impurity. It is found that the linear and third order nonlinear absorption coefficients, refractive index changes and resonance energy are quite sensitive to the presence of impurity and applied hydrostatic pressure. Moreover, the saturation in optical spectrum and relaxation time can be adjusted by increasing pressure in presence of impurity whereas the effect of hydrostatic pressure is negligible in the case of absence of hydrogenic impurity.

Investigations on 2D and 3D topography and Z-scan studies of zinc chloride co-doped L-lysinium succinate

Semi-organic NLO single crystals of zinc chloride doped L-lysinium succinate (ZnCl2-Lls) were grown using a slow evaporation method at ambient temperature. The structure and cell parameters of the grown crystal were determined by single crystal XRD and powder XRD studies. The 2-D surface morphology and elemental compositions were analyzed through SEM and EDAX studies. The 3-D surface topology was discussed using AFM images. Z-scan technique was used for measuring the third order nonlinear optical coefficients of the grown crystal.

Defects related emission and nanosecond optical power limiting in CuS quantum dots

We report optical and nonlinear optical properties of CuS quantum dots and nanoparticles prepared through a nontoxic, green, one-pot synthesis method. The presence of surface states and defects in the quantum dots are evident from the luminescent behavior and enhanced nonlinear optical properties measured using the open aperture Z-scan, employing 5ns laser pulses at 532nm. The quantum dots exhibit large effective third order nonlinear optical coefficients with a relatively lower optical limiting threshold of 2.3Jcm−2, and the optical nonlinearity arises largely from absorption saturation and excited state absorption. Results suggest that these materials are potential candidates for designing efficient optical limiters with applications in laser safety devices.

Design and preparation of novel diazo chromophores with flexible isolated groups

Novel nonlinear optical chromophore with strong electron donor, diazo electron bridge and isolation groups on both sides were synthesized and characterized by mass spectrum and hydrogen nuclear magnetic resonance. Strong electron donor and diazo electron bridge improve the nonlinear optical activities of the chromophore, large and reactive isolated groups improve the chromophore’s solubility and reduced the interaction among the chromophores. Second order nonlinear optical polymers with different chromophore loading densities were prepared and showed us the smallest glass transition temperature change. Large second order nonlinear optical coefficients were also gotten by second harmonic generation method 15.3, 27.2 and 33.4 pm/V for chromophore loading density at 10, 22.5 and 27.5 wt% respectively.

Ab-initio study on the electronic, optical and ferroelectric properties of LiOsO3

A comprehensive investigation has been made on the ground state, magnetic, ferroelectric and optical properties of the recently synthesized ferroelectric-like LiOsO3 by first-principle calculations. It is found that the ground state of perfect LiOsO3 is G type antiferromagnetic (G-AFM) order by both LSDA+U with Ueff>0eV and HSE. For the G-AFM order, when Ueff>1.75eV the charge gap opens for LiOsO3 while the gap is about 0.60eV by HSE. So the perfect LiOsO3 should be a G-AFM semiconductor. As for the Li-defected Li0.94OsO3, the Fermi level shifts to the valence bands. On the other hand the translational periodicity is destroyed by various defects, leading to the disappearance of magnetic order which is responsible for the ferroelectric metal state observed in experiment. This is proved by the decrease of the Os average magnetic moments of Li-defected LiOsO3. The calculated spontaneous polarization of perfect LiOsO3 is about 22.23μC/cm2 and the largest component of second order nonlinear optical coefficient is 80.795pm/V, which indicate that it should be a potential ferroelectric and nonlinear optical material.

One-pot synthesis of silica-hybridized Ag2S–CuS nanocomposites with tunable nonlinear optical properties

In the present work we report a simple, facile route developed for preparing silica hybridized copper sulfide and silver sulfide quantum dots at room temperature. By adjusting the concentration of the precursors, Ag2S can form Ag2S–CuS nanocomposites which are self regulated in one pot. Their crystalline, structural and optical properties have been investigated in detail, and the optical limiting nature is studied from fluence-dependent transmittance measurements employing short (5ns) laser pulses at 532nm. Ag2S nanoparticles are found to have large third order nonlinear optical coefficients with a relatively lower optical limiting threshold of 1.7Jcm−2, while the nonlinearity of the nanocomposites is found to lie in between that of Ag2S and CuS nanoparticles. These results suggest pathways for designing good quality optical limiters with tunable optical limiting efficiencies by varying the constituent nanocrystal compositions.