Exploring the optoelectronic and third-order nonlinear optical susceptibility of cross-shaped molecules: insights from molecule to material level

Photosensitizer PCBM tuning of azo dyes-based composites: Third-order nonlinear optical properties

The third-order nonlinear optical (NLO) properties of a series of poly(2,5-dialkoxy-p-phenyleneethynylene)s (PPEs) have been investigated in solution and in the solid state. In these PPEs, different alkoxy side chains are attached to the rigid-rod polymer main chain, leading to a series of polymers having an identical conjugated backbone but different supramolecular structures in the solid state. The nonresonant third-order NLO susceptibilities χ(3)(−3ω;ω,ω,ω) were measured by third-harmonic generation experiments. χ(3) values of up to 7.5 x 10-20 m2/V2 in solution and 14 × 10-20 m2/V2 in the solid state were determined. In solution, the NLO susceptibilities were found to be proportional to the content of polymer backbone, which depends on the functionalization of the PPEs. The solid state NLO susceptibilities were found to be related to the degree of long-range order in the samples, increasing with increasing order. In samples which adopt only a small extent of long-range order, the rigid-rod conjugated polymer backbones behave if they were “dissolved” in a hydrocarbon solvent, and consequently the nonlinear optical susceptibilities are comparable to those determined for solutions of these polymers. In films in which the polymer chains were found to adopt lamellar type supramolecular structures, the coplanar orientation of the conjugated polymer backbones is assumed to lead to intermolecular electronic interactions which give rise to extended conjugation lengths and hence lead to an increase of the nonlinear optical response.

Enhanced third-order nonlinear optical properties of three 2D coordination polymers based on bis(imidazole) ligands and dicarboxylic ligands

This study emphasis the solvent effect on third-order nonlinear optical (NLO) features of methyl red (MR) dye dissolved in polar solvents including ethanol, methanol, acetone, 1-propanol, DMF and DMSO using low power diode laser. Z-scan technique operating at 405nm wavelength, is used to estimate the third-order NLO features of MR dye in various solvents. The dye discloses self-defocusing nonlinear index of refraction (n2), which is determined to be the order of 10-7 cm2/W. The nonlinear coefficient of absorption (β) of MR dye displays both negative and positive value owing to saturable absorption (SA) and reverse saturable absorption (RSA), respectively. The real and imaginary components of the third-order NLO susceptibility of MR dye in polar solvents are measured to be the order of 10-6 esu and 10-7 esu, respectively. The dye exhibits a large NLO susceptibility in DMSO, which is estimated to be 1.21 × 10-6 esu. The effect of solvent spectral features on MR dye is determined by applying a multi-parameter scale called Kamlet-Abboud-Taft. The experiment results indicate that MR dye is a promising NLO material that may find applications in photonics and optoelectronics.

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

π-Conjugated organic materials exhibit high and tunable nonlinear optical (NLO) properties, and fast response times. 4'-Phenyl-2,2':6',2''-terpyridine (PTP) is an important N-heterocyclic ligand involving π-conjugated systems, however, studies concerning the third-order NLO properties of terpyridine transition metal complexes are limited. The title binuclear terpyridine Co(II) complex, bis(μ-4,4'-oxydibenzoato)-κ(3)O,O':O'';κ(3)O'':O,O'-bis[(4'-phenyl-2,2':6',2''-terpyridine-κ(3)N,N',N'')cobalt(II)], [Co2(C14H8O5)2(C21H15N3)2], (1), has been synthesized under hydrothermal conditions. In the crystal structure, each Co(II) cation is surrounded by three N atoms of a PTP ligand and three O atoms, two from a bidentate and one from a symmetry-related monodentate 4,4'-oxydibenzoate (ODA(2-)) ligand, completing a distorted octahedral coordination geometry. Neighbouring [Co(PTP)](2+) units are bridged by ODA(2-) ligands to form a ring-like structure. The third-order nonlinear optical (NLO) properties of (1) and PTP were determined in thin films using the Z-scan technique. The title compound shows a strong third-order NLO saturable absorption (SA), while PTP exhibits a third-order NLO reverse saturable absorption (RSA). The absorptive coefficient β of (1) is -37.3 × 10(-7) m W(-1), which is larger than that (8.96 × 10(-7) m W(-1)) of PTP. The third-order NLO susceptibility χ((3)) values are calculated as 6.01 × 10(-8) e.s.u. for (1) and 1.44 × 10(-8) e.s.u. for PTP.

Herein, we report the extraction of natural pigment curcumin from curcuma longa and their linear and third-order nonlinear optical (NLO) characteristics. The characterization techniques viz., UV-Visible absorption, FT-IR, Micro Raman and Gas Chromatography Mass Spectrum (GC-MS) are used to study the spectral characteristics of curcumin.Third-order NLO features of curcumin are studied using Z‒scan technique with a semiconductor diode laser working at 405nm wavelength. The natural pigment exhibits negative nonlinear index of refraction resulting from self-defocusing and positive coefficient of absorption is the consequence of reverse saturable absorption (RSA). The order of nonlinear index of refraction (n2) and nonlinear coefficient of absorption (β) is measured to be 10-7 cm2/W and 10-2cm/W, respectively. Third-order NLO susceptibility (χ(3)) and second-order hyperpolarizability (γ) of curcumin is measured to be 2.73 × 10‒7 esu and 1.67 × 10‒31 esu, respectively. A low optical limiting (OL) threshold of 0.71 mW is observed in the extracted pigment. The experimental results are supplemented by quantum mechanical calculations of the NLO parameters. The overall result finding is that curcumin extracted from curcuma longa has the potential to be novel optical candidates for photonics and optoelectronics applications.

In the present study, lanthanum oxytellurate (LOT) samples with varying La : Te ratios are successfully synthesized using a simple hydrothermal method that has enormous advantages. The prepared samples crystallize in a La2O6Te composite phase with an orthorhombic crystal system. A nanorod-like morphology is observed for each sample, and the presence of constituent elements is verified from EDX results. Chemical compositions and their oxidation states are obtained from XPS studies. Optical studies of the materials demonstrated band gap values between 2.65 and 2.78 eV, confirming the LOT samples' semiconducting nature. Broad photoluminescence (PL) spectra with peaks ranging between 650 and 750 nm were observed, and a red shift occurred by increasing the Te concentration in the samples. Overall, the samples exhibit good photoresponse characteristics under dark and light conditions with high Ion/Ioff ratios and sensitivity values. These parameters confirm the potential of LOT materials to stand out as an alternative for susceptible and effective photodetector devices. Among the samples, LOT-2 showed 10.64 μA W-1 responsivity, 5.8 × 107 Jones of detectivity, and a rise and fall time of 16.25 and 23.13 s, respectively, which was the best photodetection performance compared to the other two samples. Results from the nonlinear optical (NLO) Z-scan study demonstrated the RSA behavior and valley-peak configuration with positive n2 values corresponding to the self-focusing effect. The NLO characteristics of the materials are governed by the two-photon absorption (2PA) mechanism. Here, the LOT-2 sample displayed comparatively better results than the other two. The third-order nonlinear optical NLO susceptibility χ(3) values suggest that LOT materials have the potential to become a new candidate for various NLO applications in the coming days.

Nonlinear optical (NLO) susceptibility of Ethidium Bromide (EB) dye, an excellent NLO material, dissolved in different solvents, including ethanol, methanol, acetone, 1-propanol, DMF, and DMSO is reported. Z-scan tool is used to measure the NLO features of EB dye using open and closed aperture methods. The peak-valley transmittance graph indicating self-defocusing nonlinearity in the nonlinear refractive index of EB dye in different solvents. The nonlinear absorption coefficient showed both positive and negative nonlinearity is the result of saturable and reverse saturable absorption behavior from the open aperture curve. The absorption coefficient and nonlinear refractive index of EB dye in various solvents are found to be the order of 10-4 m/W and 10-11 m2/W, respectively. Significant second-order hyperpolarizability and third-order NLO susceptibility are observed in EB dye dissolved in DMSO. The effect of the solvent on the solute molecule is assessed using a multi-parameter scale that considered both specific and non-specific interactions. The investigation of NLO properties of EB dye is carried out using the DFT method at the B3LYP/6-311 + + G(d, p) level to compute the linear polarizability (α), first-order hyperpolarizability (β), and second-order hyperpolarizability (γ) values in different solvents. These theoretical findings are further supported by experimental results, highlighting the solvent-dependent enhancement of NLO properties.

Third-order non-linear optical susceptibility measurements of thin films of 3-methylthiophene and methylmethacrylate copolymers

The molecular orientation and chiral properties of the S-citronelloxy-cyanobiphenyl and 4′-hexyloxy-4-cyanobiphenyl monolayer at the air–water interface were investigated with optical second-harmonic generation (SHG) and Maxwell displacement current (MDC) measurements during monolayer compression. MDC was used to detect the phase transition from planar alignment phase to polar orientational phase in monolayers, and SHG was used to detect the orientation and the chirality of monolayers. The vectorial formulas for the SH process of the monolayer composed of chiral molecules were expressed using tensor components of the nonlinear optical (NLO) susceptibility, where the relationship between the NLO susceptibility and the molecular hyperpolarizabilities was also derived. According to the experiment, a polarized angle dependence measurement could reveal the chirality of this monolayer. The tensor component of the second-order NLO susceptibility, which is related to the chirality of the monolayer, was confirmed to be quite small by a fitting of the polarized angle dependence results, and it was also reasonably supported from the nonlinear molecular hyperpolarizabilities obtained from the quantum chemical calculation.

It has been well recognized that introducing corrugative configuration into nonlinear optical (NLO) susceptibility χ(2) results in an extreme enhancement of SHG power with quasi-phase-matching (QPM) scheme. The authors et al have also demonstrated significant SHG enhancement with the NLO corrugation even in the Cerenkov-radiative schemes1-3. In these recent works the NLO corrugations have been electrically introduced with either contact-electrode or corona discharges. However, organic polymers have, in general, tendency to change their optical properties, i.e. refractive index and NLO susceptibility, with ultra-violet (UV) sbsorption. Fortunately, it has been found from spectroscopy that vinylidene cyanide/vinyl acetate (VDCN/VAc) copolymer has a strong absorption band around 200 nm wavelength. In addition, it has also been preliminarily expected that the UV irradiation tends to reduce or dissipate its NLO susceptibility and the refractive index due to dissociation of the side chain in VDCN/VAc co-polymer. In the present paper we shall thus attempt to enhance the Cerenkovian SHG power with a periodic or chirped NLO χ(2) corrugation by irradiating ArF 193 nm laser source, together with discussion of the optimum UV irradiation.

Synthesis, characterization and third-order nonlinear optical properties of bromo[tri-α-(2,4-dimethyl-3-pentyloxy)subphthalocyanine]boron complex

Optical nonlinearity and ultrafast dynamics of ion exchanged silver nanoparticles embedded in soda-lime silicate glass

Herein, we report the nonlinear optical (NLO) refraction and absorption features of azo dye namely, methyl orange (MO) dissolved in ethanol, methanol, acetone, 1-propanol, DMF and DMSO. The UV-Visible absorption study reveals that the maximum absorption spectrum of MO dye appeared towards longer wavelength by increasing the solvent polarizability is the result of red shift or bathochromic shift. The Z-scan method is utilized to measure the third-order NLO features of MO dye in different polar solvents. A continuous wave laser with 5-mW power and an excitation wavelength of 405nm is employed in the Z-scan technique. The NLO features including nonlinear index of refraction (n2), nonlinear coefficient of absorption (β) and third-order NLO susceptibility (χ3) are calculated to be the order of 10-7 cm2/W, 10-2cm/W and 10-7 esu, respectively. The NLO index of refraction shows peak-valley transmittance is the result of self-defocusing and NLO absorption coefficient exhibits both positive and negative nonlinearity owing to saturable absorption (SA) and reverse saturable absorption (RSA). The effect of solvent polarizability and dipole moment on third-order NLO susceptibility of MO dye is discussed. Based on the experimental results, an azo dye MO appears to be a promising option for NLO applications in the future.