Degenerate Four-wave Mixing Technique Research Articles

Structural and ultrafast third-order nonlinearities of methyl and methoxy substituted anthracene chalcones: Z-scan, four-wave mixing, and DFT approaches

We report on the structural, thermal, linear, and ultrafast third-order nonlinear optical (NLO) properties of two novel anthracene chalcones: (2E)-1-(anthracen-9-yl)-3-(5-methylthiophen-2-yl)prop-2-en-1-one (5ML2SANC) and (2E)-1-(9-anthryl)-3-(2,4,5-trimethoxyphenyl)prop-2-en-1-one (245TMANC). The chalcones were synthesized by Claisen-Schmidt condensation reaction, and the single crystals were grown by the solvent evaporation method. The molecular structure was confirmed by FTIR and NMR spectroscopy, while the crystal structure was determined using the single crystal XRD. Both crystals belong to centrosymmetric monoclinic crystal system with space group P21/n. The Hirshfeld surface was analyzed to understand intermolecular interactions, and the band structures - including HOMO-LUMO levels, excited state energies, GCRDs and MEPs-were studied using DFT. The ultrafast third-order NLO properties were investigated by Z-scan and degenerate four-wave mixing (DFWM) techniques using Ti: Sapphire amplifier laser delivering ∼50 fs pulses at 800 nm (1 kHz, ∼4 mJ, 2 W). Two-photon absorption, positive nonlinear refraction, optical limiting and optical switching behaviors were observed by Z-scan measurements. The time-resolved DFWM show that the decay time of 5ML2SANC is ∼127 fs, while for 245TMANC it is ∼142 fs. The second hyperpolarizability (γ) measured by Z-scan, DFWM and the estimations from the DFT theory are found to be in good agreement (∼10−34 esu). The ultrafast optical response, significant NLO properties and thermal stability of the synthesized chalcones demonstrate their potential suitability in optical limiting and switching applications.

Z-scan and degenerate four wave mixing studies on newly synthesized copper complexes of curcumin

Designing novel metal complexes with high nonlinear optical (NLO) susceptibilities is a special interest for coordination compounds. They include a wider selection of metals with a variety of ligands and oxidation states, which can result in tuneable electronic capabilities. Paramagnetic Copper (II) complexes of curcumin were synthesized using different metal precursors and keeping curcumin as the base ligand. All the complexes were characterized by elemental analysis, magnetic susceptibility, and spectroscopic methods (UV–vis, FT-IR, ESR, and mass spectrometry). Nonlinear optical transmission measurements were carried out using nanosecond laser pulses with 532 nm wavelength, via a Z-scan and Degenerate four-wave mixing (DFWM) techniques. CuAcCur, CuClCur, and CuThCur complexes provided with 1.34 × 1024, 3.61 × 1024, and 4.05 × 1024 m3/W2, proved that these complexes possess excellent NLO properties and CuThCur being best among them. The NT dropped from 100 % to 78 %, 65 %, and 75 % in CuAcCur, CuClCur, and CuThCur respectively, showing that all the complexes have great potential for optical limiting (OL) application. The Conceptual-Density-Functional-Theory (CDFT) were employed to perform the theoretical analyses of complexes. Calculations on the various CDFT-based parameters such as electronegativity, HOMO-LUMO energy gap, molecular hardness, softness, dipole moment, and electrophilicity index of both species are performed. This work introduces three copper complexes with curcumin that show an excellent NLO and OL behavior.

Phase regeneration of star-16QAM using phase-sensitive amplification in graphene silicon-based organic hybrid waveguide

We theoretically demonstrate the phase regeneration of the star-16-quadrature-amplitude-modulation(star-16QAM) signal in a graphene-graphene oxide hybrid waveguide. The multi-order dispersion properties of this waveguide are tuned by graphene, where the near-zero-dispersion-point moves to right with increasing applied electrochemistry. The waveguide nonlinearity coefficient is 1.534×106/m/W and the dispersion is flat in the ultra-wide wavelength range of 1310 nm to 1860 nm by filling the waveguide with the high kerr coefficient organic material graphene oxide. The phase regeneration of the star-16QAM signal is achieved by using a dual-conjugate-pump degenerate four-wave mixing (FWM) technique, and the results show that the error-vector -magnitude (EVM) is reduced from 39.25% to 2.14%, the phase noise is effectively compressed.

Ultrafast Nonlinear Optical and Structure-Property Relationship Studies of Pyridine-Based Anthracene Chalcones Using Z-Scan, Degenerate Four-Wave Mixing, and Computational Approaches.

The structural, thermal, linear, and femtosecond third-order nonlinear optical (NLO) properties of two pyridine-based anthracene chalcones, (2E)-1-(anthracen-9-yl)-3-(pyridin-2-yl)prop-2-en-1-one (2PANC) and (2E)-1-(anthracen-9-yl)-3-(pyridin-3-yl)prop-2-en-1-one (3PANC), were investigated. These two chalcones were synthesized following the Claisen-Schmidt condensation method. Optically transparent single crystals were achieved using a slow evaporation solution growth technique. The presence of functional groups in these molecules was established by Fourier transform infrared and NMR spectroscopic data. The detailed solid-state structure of both chalcones was determined from the single-crystal X-ray diffraction data. Both crystals crystallized in the centrosymmetric triclinic space group P1̅ with the nuance of unit cell parameters. The crystals (labeled as 2PANC and 3PANC) have been found to be transparent optically [in the entire visible spectral region] and were found to be thermally stable up to 169 and 194 °C, respectively. The intermolecular interactions were investigated using the Hirshfeld surface analysis, and the band structures (highest occupied molecular orbital-lowest unoccupied molecular orbital, excited-state energies, global chemical reactivity descriptors, and molecular electrostatic potentials) were studied using density functional theory (DFT) techniques. The ultrafast third-order NLO properties were investigated using (a) Z-scan and (b) degenerate four-wave mixing (DFWM) techniques using ∼50 fs pulses at 800 nm (1 kHz, ∼4 mJ) from a Ti:sapphire laser amplifier. Two-photon-assisted reverse saturable absorption, self-focusing nonlinear refraction, optical limiting, and optical switching behaviors were witnessed from the Z-scan data. 3PANC demonstrated a stronger two-photon absorption coefficient, while 2PANC depicted a stronger nonlinear refractive index among the two. The time-resolved DFWM data demonstrated that the decay times of 2PANC and 3PANC were ∼162 and ∼180 fs, respectively. The second hyperpolarizability (γ) values determined by DFT, Z-scan, and DFWM were found to be in good correlation (with a magnitude of ∼10-34 esu). The ultrafast third-order NLO response, significant NLO properties, and thermal stability of these chalcones brands them as potential candidates for optical power limiting and switching applications.

Linear and femtosecond nonlinear optical properties of soluble pyrrolo[1,2-a] quinoxalines

We report our results from the investigations of linear and ultrafast nonlinear optical properties of a set of pyrrolo[1,2-a]quinoxalines. Using the steady state optical techniques and density functional theory calculations the linear optical properties were investigated while the non-resonant ultrafast nonlinear optical properties were studied using the degenerate four-wave mixing technique at a wavelength of 800 nm with 70 fs pulses. The investigated molecules demonstrated large off-resonant second hyperpolarizability (γ) and nonlinear refractive index (n2) values compared to similar molecular moieties with potential application in optical devices.

Degenerate four-wave mixing for measurement of magnetic field using a nanoparticles-doped highly nonlinear photonic crystal fiber.

A novel magnetic field sensor based on the degenerate four-wave mixing (DFWM) technique is theoretically proposed using a As2S3-core silica-cladding photonic crystal fiber (PCF). In order to enhance the sensitivity, we put forth a novel design of highly nonlinear PCF where the silica cladding is doped with either Au, Ag, or Al metallic nanoparticles. The effect of volume fraction of the nanoparticles within the cladding and the size of nanoparticles are considered as the control parameters in designing the magnetic field PCF sensor to obtain high sensitivity using this novel DFWM scheme. The PCF structure of the proposed sensor is optimized with the proposed pitch of 3μm and air hole diameter of 2.78μm. We consider a pumping pulsed laser light with a wavelength of 2100nm in the mid-IR regime. It has been found that the optimized PCF with Al-SiO2-cladding with small volume fraction and small nanoparticle size possess magnetic field sensitivity values of 2.74 and -0.058 nm/Oe for the Stokes and anti-Stokes gain lines.

Ultra Sensitive Nonlinear Fiber Optics-Based Refractive Index Sensor Using Degenerate Four Wave Mixing Technique in Photonic Crystal Fiber

By using degenerate four wave mixing (DFWM) analysis, we proposed a refractive index (RI) sensor in photonic crystal fiber. This novel nonlinear fiber optics-based RI sensor works on the basis of Stokes and anti-Stokes photons shift, through DFWM technique under the influence of fourth-order dispersion. Here, the frequency shift of generated photons, as a response to change in the analyte RI, is analyzed using an appropriately modified nonlinear Schrodinger equation. Sensitivity of the proposed sensor is well optimized by tuning the pump wavelength and the pump power. Finally, we achieve a maximum sensitivity of −10 200 nm/RIU for anti-Stokes shift and 56 200 nm/RIU for Stokes shift, respectively, with lattice pitch of 2.94- and 1.205- $\mu \text{m}$ diameter of the airhole and 1.5-kW pump power at the pumping wavelength of 1064.7 nm, which proves it to be an advancement in the field of biomedical and chemical applications.

All-optical switching and limiting properties of a Ru (II) Schiff-base complex for nonlinear optical applications

A salen-based ruthenium (Ru) (II) complex was synthesized for possible use in nonlinear optical device applications. The Ru complex was doped in a polymer matrix to fabricate films using a low-cost spin-coating technique. The third-order nonlinear optical parameters of the complex were investigated by Z-scan and degenerate four-wave mixing techniques. The study reveals two-order enhancement of third-order optical susceptibility χ(3) and exhibits superior limiting capability due to a reverse saturable absorption process. All-optical switching action for the films indicates that the sample can function as an optical inverter or a NOT gate. Hence, the Ru (II) Schiff-base complex materializes as a possible candidate for use in nonlinear optical devices.

Third order optical nonlinear studies and its use to estimate thickness of sandwiched films of tetra-phenyl porphyrin derivatives

Third-order nonlinear optical properties of tetra-phenyl porphyrin (H[Formula: see text]TPP) derivatives viz., H[Formula: see text]TPP(OH)[Formula: see text] and Zn(II)TPP doped in boric acid glass thin films were measured using single beam Z-scan and forward degenerate four-wave mixing (DFWM) techniques. Excited state lifetimes and absorption cross-sections were estimated from these experiments. Thickness of the porphyrin doped sandwich glass films were determined using DFWM technique for the first time. The values of nonlinear refractive index ([Formula: see text]) obtained for these systems are are found to be sensitive to the nature of substituents in porphyrin molecule. These results are interpreted in terms of delocalized [Formula: see text] electrons contributing to the third-order optical nonlinearity.

The preparation of a new type of ferrocene-based compounds with large conjugated system containing symmetrical aromatic vinyl with Schiff base moieties and the study of their third-order nonlinear optical properties

Herein we reported the preparation of a new type of ferrocene-based compounds with large conjugated system containing symmetrical aromatic vinyl and Schiff base moieties and the study of their third-order nonlinear optical (NLO) properties. Their third-order NLO properties were measured using femtosecond laser and degenerate four-wave mixing (DFWM) technique. The obtained χ(3), n2 and γ values of these molecules were found in the range of 0.998–1.429×10−12esu,1.847–2.646×10−11esu and 1.026–1.449×10−30esu, respectively. The response time ranged from 43.65fs to 61.71fs. The results indicate that these compounds have potential nonlinear optical applications.

Synthesis and optical properties of soluble low bandgap poly (pyrrole methine) with alkoxyl substituent

A soluble low bandgap poly (pyrrole methine) with alkoxyl substituent, poly {(3-hexanoyl)pyrrole-[2,5-diyl(p-tetradecyloxybenzylidene)]} (PHPDTBE), was synthesized and characterized by 1H nuclear magnetic resonance (1H-NMR), Fourier transform-infrared (FT-IR), elemental analysis (EA) and gel permeation chromatography (GPC). PHPDTBE was readily soluble in weak polar organic solvents. The absorption peaks of PHPDTBE solution and film were located at around 458 and 484 nm, respectively. The optical bandgaps of PHPDTBE film for indirect allowed and direct allowed transitions were measured to be 1.66 and 2.35 eV, respectively. PHPDTBE film had few defects in the energy band and the Urbach energy of PHPDTBE film was calculated to be about 0.19 eV. The resonant third-order nonlinear optical susceptibilities of PHPDTBE solution and film measured by degenerate four-wave mixing (DFWM) technique at 532 nm were all in the order of 10–8 esu, which was about 1~3 orders of magnitude larger than that of the other ordinary π-conjugation polymers.

Synthesis, characterization and third-order nonlinear optical properties of symmetrical ferrocenyl Schiff base materials

Six symmetrical ferrocenyl Schiff base materials were synthesized and characterized by UV, 1H NMR, mass spectrometry (MS) and elemental analysis. Their off-resonant third-order nonlinear optical properties were measured using femtosecond laser and degenerate four-wave mixing (DFWM) technique. The third-order nonlinear optical susceptibilities χ(3) were 1.961–6.363×10−13esu. The nonlinear refractive indexes n2 were 3.609–11.716×10−12esu. The second-order hyperpolarizabilities γ of these molecules were 1.967–6.388×10−31esu. The response time were 45.759–73.079fs. The results indicate that these materials have potential nonlinear optical applications.

Fast Optical Switching Using Cyanine Dye-Doped Nematic Liquid Crystal

Two kinds of cyanine dye were doped respectively in 4-cyano-4'-pentylbiphenyl (5CB) at a concentration ca. 1.0 wt%, and the mixture was sandwiched between two pieces of rubbed glass plates. The third-order nonlinear optical responses of cyanine dye-doped 5CB layers were measured for light polarized parallel to the oriented direction by the resonant femtosecond forward degenerate four-wave mixing technique at 820 nm. The time resolution of the system was ca. 0.3 ps. The amplified spontaneous emission spectra of cyanine dye-doped 5CB layers indicate that the decay of the slow response was accelerated with increasing laser power. The population grating disappears within ca. 5 ps.

Six [Tp*WS3Cu2]-based clusters derived from [Et4N][Tp*WS3], Cu(i) salts and phosphine ligands: syntheses, structures and enhanced third-order NLO properties

Treatment of [Et4N][Tp*WS3] (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) (1) with CuX (X = Br, SCN) and PPh3 or 1,1-bis(diphenylphosphino)methane (dppm) produced two neutral trinuclear clusters [Tp*W(μ3-S)(μ-S)2Cu2Br(PPh3)] (2) and [Tp*W(μ3-S)(μ-S)2Cu2(SCN)(dppm)]2·MeCN·Et2O (3·MeCN·Et2O). Reactions of 1 with [Cu(MeCN)4]PF6, NH4PF6 and 1,3-bis(diphenylphosphino)propane (dppp), N,N-bi(diphenylphosphanylmethyl)-2-aminopyridine (bdppmapy), N,N,N',N'-tetra(diphenylphosphanylmethyl)ethylenediamine (dppeda), or 1,4-N,N,N',N'-tetra(diphenylphosphanylmethyl)benzenediamine (dpppda) afforded four clusters containing butterfly-shaped [Tp*WS3Cu2] cores, [Tp*W(μ3-S)(μ-S)2Cu2(dpppds)](PF6)·1.25MeCN (dpppds = 1,3-bis(diphenylphosphino)propane disulfide) (4·1.25MeCN), [Tp*W(μ3-S)(μ-S)2Cu2(bdppmapy)](PF6)·3MeCN (5·3MeCN) and {[Tp*W(μ3-S)(μ-S)2Cu2]2(L)]}(PF6)2·Sol (6·Et2O: L = dppeda, Sol = Et2O; 7·1.25MeCN: L = dpppda, Sol = 1.25MeCN). Compounds 2-7 were characterized by elemental analysis, IR, UV-Vis, (1)H and (31)P{(1)H} NMR spectra, electrospray ion mass spectra (ESI-MS) and single-crystal X-ray diffraction. Compound 2 or 3 has a butterfly-shaped [Tp*WS3Cu2] core in which one [Tp*WS3] unit binds two Cu(I) centers via one μ3-S and two μ-S atoms. In the cationic structure of 4 or 5, one in situ-formed dpppds or bdppmapy combines with the [Tp*WS3Cu2] core via each of its two S atoms or two P atoms coordinated at each Cu(I) center. In the bicationic structure of 6 or 7, two [Tp*WS3Cu2] cores are linked by one dppeda or dpppda bridge to form a bicyclic structure. The isolation of 2-7 with unstable [Tp*WS3Cu2] cores may be ascribed to the coordination of P- or S-donor ligands at Cu(i) centers of these cores. The third-order nonlinear optical (NLO) properties of 2-7 in DMF were also investigated by using the femtosecond degenerate four-wave mixing (DFWM) technique at 800 nm.

Effects of acid anions, major metallic elements, and chlorides on Li detection by DFWM in graphite furnace

In trace Li analysis with degenerate four-wave mixing (DFWM) method, acid anions and major metallic elements are dominant interferences in Li-containing samples. To better use DFWM technique to analyze trace Li in actual samples, we study their effects on Li DFWM signal intensity. It is found that K, Cs, and Ni can enhance the Li DFWM signal, SO2-4..., PO3-4..., Cl-, and Ca can cause significant suppression, and NO3-, Mg, Ba, Sr, and Na almost have no effects. Finally, we use H3BO3 to eliminate the depressive effects of chlorides on Li DFWM signal. The result is also of reference in other trace elements analysis with DFWM.

Self-Aggregation Enhanced Third-Order Optical Nonlinearities of Aryloxy Substituted Zinc Phthalocyanines

Third-order optical nonlinearities of three aryloxy substituted phthalocyanines are measured by femtosecond forward degenerate four-wave mixing technique at 800 nm. Ultrafast optical responses are observed and the magnitude of the second-order hyperpolarizabilities γ of the phthalocyanines is measured to be as large as 10−31 esu. Due to the enhancement of J-aggregates, the γ value of an aryloxy substituted zinc phthalocyanine in chloroform is approximately 2.2 times larger than that of the dye in methanol. Moreover, the morphologies of aryloxy substituted zinc phthalocyanine in chloroform exhibit that the nanowires with a diameter of 50–100 nm are connected to each other to form an indefinite network structure, while no aggregates are detected when the samples are prepared from a solution in the methanol.

Third-Order Nonlinear Optical, Optical Power Limiting, and All-Optical Switching Studies on Palladium Complexes

The authors report the third-order nonlinear optical properties of two palladium complexes in solution and film form using nanosecond Z-scan technique at 532 nm. The nonlinear refractive index n2 of the investigated complexes is found to be negative. Both complexes exhibit strong reverse saturation absorption and show good optical power limiting of nanosecond pulses. Also the third-order nonlinear optical susceptibility of the complexes was determined using degenerate four-wave mixing technique. The variations of nonlinear response on donor and acceptor type of units present in the complexes are studied. The all-optical switching phenomenon was also demonstrated by using nanosecond pump-probe technique.

Study of optical phase conjugation in amorphous Znx–Sy–Se100−x−y chalcogenide thin films using degenerate four-wave mixing

Degenerate four-wave mixing (DFWM) experiment is performed to obtain light wavefront inversion (phase conjugation) in semiconducting chalcogenide thin films. Third order nonlinearity of amorphous Znx–Sy–Se100−x−y chalcogenide thin films using DFWM technique is studied at second harmonic of Nd:YAG laser. Influence of total input irradiance on phase conjugate signal is deliberated using log–log plot that has a slope of three and hence implies third order nonlinearity. The dependence of phase conjugate signal on forward beam and backward beam is also studied. The period of the grating formed by interference of forward and probe beam is determined. As the temporal overlapping and sample thickness conditions are satisfied, the third order nonlinear susceptibility, figure of merit and nonlinear refractive index of amorphous films are estimated. The nonlinear behavior is analyzed in terms of decrease in band gap with increasing Zinc and decreasing Sulfur content.

A theoretical study on the structural dependences of third-order optical nonlinearities of heterocycle-substituted polymethine cyanine chromophores

The linear and third-order nonlinear optical properties of four polymethine cyanines (PC-1–PC-4) were investigated by UV–visible absorption spectroscopy and degenerate four-wave mixing (DFWM) technique. The second-order hyperpolarizabilities γ of the four chromophores achieve 10−31esu. The dependence of their third-order optical nonlinearities on the molecular structure was discussed based on density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The calculated second-order hyperpolarizabilities γ well-reproduce the experimental trends. The results show that the third-order optical nonlinearities of the chromophores can be drastically enhanced by bulky heteroatom (such as selenium) with low electro-negativity, or extended π-conjugated terminal group.

Synthesis, characterization, and nonlinear optical responses of nickel(II) complexes with phenanthroline-based ligands

Three nickel(II) complexes with phenanthroline-based ligands were synthesized and characterized by UV–visible, IR, MS, and elemental analysis. Their off-resonance third-order nonlinear optical (NLO)properties were measured using a femtosecond laser and the degenerate four-wave mixing technique. The third-order NLO susceptibilities χ (3) were 3.45–4.37 × 10−13 esu. The second-order hyperpolarizabilities γ of the molecules were 3.46–4.36 × 10−31 esu. The response times were 50–74 fs. The influence of the molecular structure on the third-order optical nonlinearity was analyzed. The results show that highly polarizable delocalized π-conjugated electron system is the key factor leading to strong third-order optical nonlinearity.