Femtosecond Degenerate Four-wave Mixing Research Articles

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, 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.

Syntheses, third-order optical nonlinearity and DFT studies on benzoylferrocene derivatives

A series of benzoylferrocene derivatives were synthesized and their third-order nonlinear optical (NLO) properties were evaluated in N,N-dimethyl-formamide at 800 nm using femtosecond degenerate four-wave mixing. The third-order NLO susceptibilities of synthesized compounds were 3.065–7.859 × 10−13 esu, with the response times in 49–70 fs. The second-order hyperpolarizabilities of the molecules of the compounds were 1.018–2.611 × 10−31 esu. The Density Functional Theory was used to calculate these benzoylferrocene derivatives. The theoretical study showed that the third-order NLO properties were increased with the increasing electron-withdrawing ability, which is accordance with the decreasing energy gap between the highest occupied and the lowest unoccupied molecular orbital. With the increasing of electron-withdrawing ability, the transferred charge to the substituent was increased and the affection on the electronic reallocate was increased. The experiment and theoretical results showed that the benzoylferrocene derivatives had potential nonlinear optical applications.

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.

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.

Atomic wave-packet dynamics and third-harmonic generation in sodium

In femtosecond degenerate four-wave mixing experiments in sodium vapor, quantum beats are observed at the wavelength of the third harmonic when the fundamental beams are three-photon resonant. The period of beating, which corresponds to fine structure energy-level splitting, does not change with the atomic number density, buffer gas pressure, or laser intensity. Surprisingly, the third-harmonic signal is observed only at negative time delays for the transient grating pulse sequence. We relate this to the well-known interference effect between excitation pathways involving the fundamental and the third-harmonic fields, which leaves atoms virtually unexcited and prevents formation of population grating.

Novel [Tp*WS3Cu2]-Based Coordination Compounds: Assembly, Crystal Structures, and Third-Order Nonlinear Optical Properties

Treatment of [Et4N][Tp*WS3] (1) (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) with [Cu(MeCN)4]PF6 and NH4PF6 (molar ratio = 1:2:1) in excess pyridine (py) produced one discrete trinuclear cluster [Et4N][Tp*WS3Cu2(py)3](PF6)2 (2). Reactions of 1 with [Cu(MeCN)4]PF6, NH4PF6, and 4,4′-bipyridine (4,4′-bipy) (or 1,2-bis(4-pyridyl)ethane (bpea)) (molar ratio = 1:2:1:2) afforded a two-dimensional (2D) [Tp*WS3Cu2]-based cationic polymer {[Tp*WS3Cu2(4,4′-bipy)1.5](PF6)·2MeCN}n (3·2MeCN) and a one-dimensional (1D) [Tp*WS3Cu2]-based cationic polymer {[(Tp*WS3Cu2)2(bpea)3](PF6)2·2DMF}n (4·2DMF), respectively. Analogous reactions of 1 with CuCN, NH4PF6, and 4,4′-bipy (or 1,2-bis(4-pyridyl)ethylene (bpee)) (molar ratio = 1:2:1:2) gave rise to a 2D [Tp*WS3Cu2]-based polymer {[Tp*WS3Cu2(μ-CN)(4,4′-bipy)0.5]·MeCN}n (5·MeCN) and a three-dimensional (3D) [Tp*WS3Cu2]-based anionic polymer {[Et4N][(Tp*WS3Cu2)2{Cu(μ-CN)2.5}2(bpee)]·3MeCN}n (6·3MeCN), respectively. Compounds 2–6 were characterized by elemental analysis, IR, UV–vis, 1H NMR, and single-crystal X-ray diffraction. The cluster cation of 2 has a butterfly-shaped [Tp*WS3Cu2] core structure in which one [Tp*WS3] unit binds two Cu atoms via one μ3-S and two μ-S atoms. 3 consists of one 2D (6,3) network in which butterfly-shaped [Tp*WS3Cu2] units are interlinked by the 4,4′-bipy ligands. 4 contains butterfly-shaped [Tp*WS3Cu2] units that are interconnected by bpea bridges to form one 1D zigzag chain. 5 holds another 2D (6,3) network in which the 1D [{Tp*WS3Cu2}2(μ-CN)2]n chains are bridged by 4,4′-bipy ligands. 6 possesses a 3-connected 3D (103) anionic net in which each 2D [{(Tp*WS3Cu2)2Cu2(μ-CN)4}4(μ-CN)4(bpee)2]n4n– network is interlinked to its neighboring ones via pairs of bpee ligands. The isolation of 2–6 with unstable [Tp*WS3Cu2] cores may be ascribed to the coordination of N-donor ligands or linkers at Cu(I) centers of these cores and the formation of polydimensional [Tp*WS3Cu2]-based frameworks (in the case of 3–5). The third-order nonlinear optical (NLO) properties of 2–6 in DMF were also investigated by using a femtosecond degenerate four-wave mixing (DFWM) technique at 800 nm.

Synthesis of nickel(II) complexes containing modified phenanthroline ligands for potential nonlinear optical applications

Three nickel(II) complexes containing modified phenanthroline ligands were synthesized and characterized by UV–visible, IR, MS and elemental analysis. Their off-resonant third-order nonlinear optical properties were measured using femtosecond laser and degenerate four-wave mixing technique. The third-order nonlinear optical susceptibilities χ(3) were 3.74–4.23×10−13esu. The nonlinear refractive indexes n2 were 6.88–7.77×10−12esu. The second-order hyperpolarizabilities γ of the molecules were 3.74–4.22×10−31esu. The response times were 58–75fs. The results show that these complexes have potential nonlinear optical applications.

Synthesis, third-order nonlinear optical properties and theoretical analysis of vinylferrocene derivatives

A series of vinylferrocene derivatives were synthesized from the reaction of ferrocenecarboxaldehyde, alcohol, and triphenylphosphonium bromide in a one-pot, solid-state reaction. Their third-order nonlinear optical (NLO) properties were evaluated in N,N-dimethylformamide at 800 nm using femtosecond degenerate four-wave mixing. The third-order NLO susceptibilities of the compounds were 2.55–3.78 × 10 −13 esu. The second-order hyperpolarizabilities of the molecules were 2.42–3.60 × 10 −31 esu. The response times were 51–98 fs. The energy of the Highest Occupied Molecular Orbital (HOMO), the Lowest Unoccupied Molecular Orbital (LUMO), the energy gap of the HOMO and LUMO ( E gap ), natural charge, and molecular orbitals are performed by the Density Function Theory (DFT). The DFT study showed that the third-order NLO properties were increased with the increasing electron-withdrawing ability in accordance with the decreasing E gap and the increasing charge transfer among the donor, π-bridge, and the acceptor. The experiment and theoretical results show that the vinylferrocene derivatives have potential nonlinear optical applications. • A series of vinylferrocene derivatives were synthesized. • The third-order nonlinear optical properties were measured using femtosecond degenerate four-wave mixing. • The energy of HOMO, LUMO, E gap , natural charge, and MOs are performed by DFT.

Assembly of new Mo/Cu/S clusters from [Et4N][Tp*MoS(S4)] and Cu(i) salts: syntheses, structures and third-order nonlinear optical properties

Reactions of [Et4N][Tp*MoS(S)4] (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) (1) with 3 equiv. of CuX (X = Cl, Br, I, CN) or [Cu(MeCN)4]ClO4 in CH2Cl2-MeCN or CH2Cl2-DMF afforded [Et4N]2[Tp*Mo(μ3-S)3(CuCl)3(μ3-Cl)] (2), [Et4N][Tp*Mo(μ3-S)3(CuX)3] (3: X = Br; 4: X = I), [Et4N][Tp*MoO(μ-S)2(CuX)] (5: X = I; 6: X = CN) and [Tp*Mo(μ3-S)3Cu3(μ3-S')]4 (7). Compounds 2-7 were characterized by elemental analysis, IR spectra, UV-vis spectra, (1)H NMR, electrospray ion mass spectra (ESI-MS) and X-ray crystallography. The cluster dianion of 2 has a complete cubane-like [Tp*Mo(μ3-S)3(CuCl)3(μ3-Cl)] structure while the anion of 3 or 4 consists of an incomplete cubane-like [Tp*Mo(μ3-S)3(CuX)3] structure. The anion of 5 or 6 has a binuclear structure, in which one [Tp*MoO(μ-S)2] moiety and one CuX unit are linked by a pair of μ-S atoms. The structure of 7 may be considered as a supercube whose eight corners are occupied by four incomplete cubane-like [Tp*Mo(μ3-S)3Cu3] fragments and four μ3-S' atoms. The third-order nonlinear optical (NLO) properties of 2-6 in DMF were investigated by femtosecond degenerate four-wave mixing (DFWM) technique with a 80 fs pulse width at 800 nm. Compounds 2-6 exhibited good NLO performances and their NLO responses were enhanced relative to that of 1.

Anisotropy in Third-Order Nonlinear Optical Susceptibility of the Stretch-Oriented Chrysophenine-Doped Poly(vinyl alcohol) Films

Stretch-oriented chrysophenine-doped poly(vinyl alcohol) (PVA) films were prepared at temperatures above the glass transition temperature of PVA. The optical absorption spectra of the stretch-oriented films exhibited a very high anisotropy (anisotropy ratio = 13). The third-order nonlinear optical properties of chrysophenine in stretch-oriented PVA films were measured by the resonant femtosecond degenerate four-wave mixing (DFWM) technique. The anisotropy ratio of the DFWM signal intensity was greater than 1000. The value of third-order nonlinear optical susceptibility of a uniaxially stretch-oriented chrysophenine-doped PVA film was 6.9×10-13 esu.

Halide-Directed Synthesis of Coordination Polymers [Hg2X4(ppt)]n(X=I and Br, ppt=1-(4-Pyridyl)-pyridinium-4-thiolate) with Different One-Dimensional Chain Structures and Third-Order Nonlinear Optical Properties

Solvothermal reactions of HgX2 (X=I, Br) with 4,4'-dipyridyl disulfide (dpds) in acetonitrile gave rise to two one-dimensional polymers (Hg2X4(ppt))n (ppt=1-(4-pyridyl)-pyridinium-4-thiolate; X=I (1), Br (2)). In the structures of 1 and 2, the ppt ligand was in situ generated from the Hg(II)-engaged cleavage of both S—S and S—C bonds of dpds and the subsequent rearrangement reactions under solvothermal conditions. Although compounds 1 and 2 have similar chemical for- mula, 1 crystallizes in the orthorhombic space group Ima2 and holds a 1D non-centrosymmetric zigzag chain while 2 crystal- lizes in the orthorhombic space group Pnma and has a 1D centrosymmetric zigzag chain. Such a difference in structural symmetry between 1 and 2 may be due to the fact that the radius of iodide is larger than that of bromide. The third-order nonlinear optical (NLO) behaviours of 1 and 2 in DMF were investigated by using femtosecond degenerate four-wave mixing technique. Compound 1 exhibited relatively strong NLO responses while compound 2 showed nothing. Such a remarkable difference in the NLO property may be due to the fact that iodide is a better electron donor than bromide, which allows more efficient spin-orbital coupling, and facilitates intersystem crossing and more efficient usage of triplet excited state absorption. Keywords halide-directed; coordination polymer; solvothermal synthesis; structure; nonlinear optical properties

Alkali-Responsive Absorption Spectra and Third-Order Optical Nonlinearities of Imino Squaramides

Third-order optical nonlinearities and dynamic responses of two imino squaramides under neutral and base conditions were studied using the femtosecond degenerate four-wave mixing technique at 800 nm. Ultrafast optical responses have been observed and the magnitude of the second-order hyperpolarizabilities of the squaramides has been measured to be as large as 10−31 esu. The absorption spectra, color of solution, and third-order optical nonlinearities of two imino squaramides change with the addition of sodium hydroxide. The γ value under the base condition for each dye is approximately 1.25 times larger than that under neutral conditions.

Measurement of field-free alignment of jet-cooled molecules by nonresonant femtosecond degenerate four-wave mixing

A femtosecond degenerate four-wave mixing (fs-DFWM) technique for probing the alignment of molecules is described. The rotational wave packet generated by a strong pump beam modulates the nonresonant third-order susceptibility of the gas and this modulation is observed using a noncollinear background-free setup. As a demonstration of the technique, we measure the alignment of a linear molecule (nitrogen), a symmetric top (benzene), and an asymmetric top (iodobenzene) in a supersonic jet. The measured signal is shown to agree well with calculations of the nonresonant third-order susceptibility from the solution of the time-dependent Schr\"odinger equation. The pump-DFWM measurement scheme can be used with dilute jet-cooled targets, allows arbitrary pump pulses to be used, and is rapid enough to be incorporated into a feedback optimization loop. The scheme can easily be made polarization-sensitive, indicating the possibility of measuring and optimizing three-dimensional alignment of asymmetric-top molecules.

Resonant Third-Order Optical Nonlinearities of the Stretch-Oriented Cyanine-Dye-Doped Poly(vinyl Alcohol) Films

Stretch-oriented cyanine-dye-doped poly(vinyl alcohol) (PVA) films were prepared at temperatures above the glass transition temperature of PVA. The optical absorption spectra of the stretch-oriented films exhibited an anisotropy. The third-order nonlinear optical susceptibilities of the stretch-oriented films were measured parallel and perpendicular to the stretching direction by the resonant femtosecond degenerate four-wave mixing (DFWM) technique, and a high anisotropic X(3) was observed for the uniaxially stretch-oriented cyanine-dye-doped PVA films.

Femtosecond Rotational Raman Coherence Spectroscopy of Cyclohexane in a Pulsed Supersonic Jet

We combine the technique of femtosecond degenerate four-wave mixing (fs-DFWM) with a high repetition-rate pulsed supersonic jet source to obtain the rotational coherence spectrum (RCS) of cold cyclohexane (C(6)H(12)) with high signal/noise ratio. In the jet expansion, the near-parallel flow pattern combined with rapid translational cooling effectively eliminate dephasing collisions, giving near-constant RCS signal intensities over time delays up to 5 ns. The vibrational cooling in the jet eliminates the thermally populated vibrations that complicate the RCS coherences of cyclohexane at room temperature [Brügger, G.; et al. J. Phys. Chem. A 2011, 115, 9567]. The rotational cooling reduces the high-J rotational-state population, yielding the most accurate ground-state rotational constant to date, B(0) = 4305.859(9) MHz. Based on this B(0), a reanalysis of previous room-temperature gas-cell RCS measurements of cyclohexane gives improved vibration-rotation interaction constants for the ν(32), ν(6), ν(16), and ν(24) vibrational states. Combining the experimental B(0)(C(6)H(12)) with CCSD(T) calculations yields a very accurate semiexperimental equilibrium structure of the chair isomer of cyclohexane.

Degenerate four-wave mixing determination of third-order optical nonlinearities of three mixed ligand nickel(II) complexes

Abstract Three mixed ligand nickel(II) complexes were synthesized and characterized by UV–visible, IR, MS and elemental analysis. Their off-resonant third-order nonlinear optical properties were measured using femtosecond laser and degenerate four-wave mixing technique. The third-order nonlinear optical susceptibilities χ (3) were 3.20–3.51 × 10 −13 esu. The nonlinear refractive indexes n 2 were 5.89–6.45 × 10 −12 esu. The second-order hyperpolarizabilities γ of the molecules were 3.20–3.50 × 10 −31 esu. The response times were 55–81 fs. The results show that these complexes have potential nonlinear optical applications.

Synthesis and third-order optical nonlinearities of ferrocenyl Schiff base

Four ferrocenyl Schiff bases were synthesized from ferrocenecarboxaldehyde and aromatic amine. The yields were 46–73%. These compounds have a D-A structure and third-order nonlinear optical (NLO) properties. The third-order nonlinear optical properties of the compounds were measured using femtosecond degenerate four-wave mixing. The third-order NLO susceptibilities of the compounds were 2.21–3.32×10−13esu. The second-order hyperpolarizabilities of the molecules were 2.10–3.15×10−31esu. The response times were 42–63fs.

Third-Order Optical Nonlinearity of a 1,3-Bis(2,4,6-Trihydroxy-Phenyl)Squaraine

The magnitude and dynamic response of the third-order optical nonlinearity of a 1,3-bis(2,4,6-trihydroxy-phenyl)squaraine was measured by femtosecond degenerate four-wave mixing (DFWM) technique at 800 nm. Ultrafast optical response has been observed and the magnitude of the second-order hyperpolarizability of the studied squaraine was measured as large as 3.8 ×10-31 esu. The large optical nonlinearities of the squaraine can be attributed to their rigid and intramolecular charge transfer structure, and the instantaneous NLO response of squaraine is mainly contributed from the electron delocalization.

Large Amplitude Motions in Cyclopentene and 1-Butene: Quantum Chemical Insights into the Ground- and Excited State Potential Energy Surfaces

Abstract The ring-puckering motion in cyclopentene as well as the hindered internal rotation around the central C–C bond in 1-butene have been studied by high-level quantum chemical calculations. Relevant potential energy surfaces of these molecules along these large-amplitude motions are provided as well as rotational constants are given allowing for thorough comparison with recent results from time-resolved femtosecond degenerate four-wave mixing (fs DFWM) spectroscopy. Emphasis is put on the performance of various post-Hartree Fock methods, the required level of electron correlation as well as the basis set quality.