Large Third-order Nonlinear Optical Susceptibility Research Articles

Ultrafast photophysical and nonlinear optical properties of novel free base and axially substituted phosphorus (V) corroles

The progression in synthetic procedures over the last two decades gave admittance to a wide variety of corroles for suitable potential applications such as photovoltaics, photonics, and bio-imaging. In this communication, we present results from our investigations of ultrafast photophysical processes and third-order nonlinear optical properties of newly synthesized donor-acceptor based free-base [(C6F5)3] and phosphorus [P-(OH)2(C6F5)3] corroles. The global analysis of the femtosecond transient absorption data based on the compartmental model revealed the corresponding time constants of several photophysical processes such as (a) internal conversion (τIC) in the 260–280 fs range (b) vibrational relaxation (τVR) in the 2.5-5 ps range and (c) nonradiative relaxation times (τnr) in the 4.15–7.6 ns range and finally (d) triplet lifetimes in the range of 25–50 μs. The two-photon absorption (TPA) cross-section measurements were performed using the femtosecond, kHz pulse Z-Scan technique at 600 nm and 800 nm and the retrieved TPA cross-section values were in the range of ~102 GM. Degenerate four-wave mixing measurements illustrated a large third-order nonlinear optical susceptibility χ(3) with a magnitude of 6.9 × 10−14 esu and instantaneous (sub-picosecond) response, suggesting a pure electronic contribution to the nonlinearity of these corroles. The discoveries from this study may help further to extend the capability of corroles as NLO materials for photonic applications.

Mesoporous silica membranes loaded with Ag or Au nanoparticles and optical nonlinear susceptibilities

As a template, mesoporous silica membranes were used to trap Ag or Au nanoparticles into their channels without aggregation, contributing to large third-order nonlinear optical susceptibilities. We compared the susceptibility values of the composite mesoporous membranes synthesized by different electrodeposition methods. Results show that differential pulse amperometry (DPA) electrodeposition method gives rise to larger susceptibilities than that by potentiostatic electrodeposition method. DPA electrodeposition provides buffer time for Ag ions to diffuse to the reaction interface to supply Ag ions concentration, resulting more in-channel Ag nanoparticles. Among the synthesized composite membranes loaded with Ag, samples synthesized by DPA method in lower electrolyte concentration possess the largest susceptibility, which agrees well with results of XRD patterns and HR-TEM images. Similarly, the synthesized composite membranes loaded with Au also show the best susceptibility using this strategy under optimal voltage of −0.2V.

Plasmon resonance enhanced large third-order optical nonlinearity and ultrafast optical response in Au nanobipyramids

The third-order optical nonlinearity and response time of Au nanobipyramids have been investigated by using optical Kerr effect technique. Large third-order nonlinear optical susceptibility (χ(3)) and ultrafast optical response time have been obtained at the longitudinal surface plasmon resonance (LSPR) wavelength. As the excitation laser wavelength varies from non-resonance wavelength of 780 nm to the LSPR wavelength of 825 nm, χ(3) increases from 7.4 × 10−14 to 3.9 × 10−13 esu, the fast component of the response time decreases from 141 ± 23 to 83 ± 8 fs and the ratio of the fast component remains around 48%, while the slow response time decreases from 3200 ± 200 to 2310 ± 158 fs. The large enhancement of χ(3) is due to the large local field enhancement caused by the surface plasmon resonance, and the shortening of the response times are induced by the increased probability of the electron-electron and electron-phonon scatterings in the nanosystem. This significant ultrafast optical property in Au nanobipyramids has great application in future ultrafast information processors.

Adjustable third-order nonlinear optical properties of the spin coating phenoxazinium–PMMA films

The third-order nonlinear optical properties of spin coating poly(methyl methacrylate) films doped with 3,7-bis(diethylamino)phenoxazin-5-ium chloride (1) are reported. The third-order nonlinear optical properties were tested by Z-scan technology with nanosecond laser beam at 532 nm. The third-order nonlinear absorptions change from reverse saturation absorption to saturation absorption with increasing percentage of the phenoxazinium dye in the poly(methyl methacrylate) film. The different forms of the spin coating films were obtained by atomic force microscopy and transmission electron microscope, and the different aggregation phenomenon of the phenoxazinium in the films can explain the adjustable third-order nonlinear absorption phenomena. Moreover, large third-order nonlinear optical susceptibilities (up to 10−7 esu) and high second hyperpolarizabilities (up to 10−28 esu) are found with these films. The results indicate that the phenoxazinium dye is the potential material for the third-order nonlinear optical application.

Third-order nonlinear optical properties of the poly(methyl methacrylate)-phenothiazinium dye hybrid thin films

The third-order nonlinear optical properties of poly(methyl methacrylate) films doped with charge flowable 3,7-di(piperidinyl)phenothiazin-5-ium chloride, which tested by Z-scan method with nanosecond laser beam at 532nm, are reported. Large third-order nonlinear optical susceptibilities (up to 10−7esu) and high second hyperpolarizabilities (up to 10−27esu) are found. The third-order nonlinear absorptions change from reverse saturated absorptions to saturated absorptions with different percentage of the phenothiazinium dye in the poly(methyl methacrylate) films, which can be explained by the accumulation phenomenon of the phenothiazinium. The results suggest that the phenothiazinium salt is a promising material for third order non-linear applications.

Ultra-fast all-optical switching in MEH-PPV photonic crystals with resonantly enhanced nonlinearity

Photonic crystal all-optical switching is realized in two-dimensional nonlinear photonic crystals made of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]. Organic polymer films are fabricated by a slow evaporation method. Under resonant excitation, the organic matrix provides very large third-order nonlinear optical susceptibility. An operating pump energy as low as 514 pJ/cm2 and a high switching efficiency of 70% are achieved for the photonic crystal optical switching. A switching time of 45.6 ps is maintained due to fast Forster transfer of excitons.

Optical Bistability of Terthiophene/Poly(methyl methacrylate) Composite Film Prepared Using Spin-Coating

Owing to advancing large-scale optical communications technology, all-optical devices have attracted attention in high-speed data communication systems. We measured the characteristics of the optical bistability of elements fabricated using a terthiophene/poly(methyl methacrylate) (PMMA) composite film and a prism, and investigated the origin of the optical bistability. The measured optical bistabilities revealed excellent hysteresis characteristics. The shift of the on-off position of the optical bistability decreased with the composite film with a large third-order nonlinear optical susceptibility.

Stilbene-containing polyactylenes: Molecular design, synthesis, and relationship between molecular structure and NLO properties

Polyacetylenes (P1–P4) containing different stilbene groups, [(CHC) PhCHCHPhR]n(ROCmH2m+1 (m = 4 (P1), 10 (P2), 16 (P3)), or NO2 (P4)) were designed and synthesized, respectively, using [Rh(nbd)Cl]2 as a catalyst. Their structures and properties were characterized and evaluated by FTIR, 1H-NMR, 13C-NMR, GPC, and UV, PL, respectively. The optical limiting and nonlinear optical properties were investigated by using a frequency doubled, Q-switched, mode-locked Continuum ns/ps Nd:YAG laser system and their optical limiting mechanism was discussed. It is surprising to see that the stilbene pendants endow the polyacetylenes with a high thermal stability (Td ≥ 270 °C), novel optical limiting properties and large third-order nonlinear optical susceptibilities (up to 4.61 × 10−10 esu). The optical limiting mechanism is mainly originated from reverse saturable absorption of molecules. In addition, it is found that the polymer with electron accepted NO2 moiety exhibits better optical properties than that with electron donated alkoxy group because of larger π electron delocalization and dipolar effect. The strong interaction between stilbene pendants and the polyene main chain significantly results in red-shift of fluorescence emitting peak. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4529–4541, 2008

Strong stacking behavior and large third-order nonlinear optical susceptibility χ(3) of head-to-head-type poly(3-alkynylthiophene-2,5-diyl), HH-P3(C [tbnd]CR)Th

The head-to-head-type poly(3-alkynylthiophene-2,5-diyl) HH-P3(C CR)Th has been shown to exhibit a strong tendency to self-assemble. The UV–vis spectrum of HH-P3(C CDec)Th (Dec = decyl) in 1,2-dichlorobenzene at 131 °C showed a peak at λ max = 520 nm, which shifted to λ max = 553 nm at 25 °C, with a shoulder peak at 608 nm. However, the UV–vis spectrum of an HH-P3(C CDec)Th film showed a more pronounced shift in its UV–vis absorption peak to a longer wavelength. These phenomena are the characteristics of the self-assembly of the polymer molecule. The HH-P3(C CDec)Th film had a large third-order nonlinear optical susceptibility χ (3) of 3.6 × 10 −11 esu.

Origin of Near-Infrared Absorption and Large Second Hyperpolarizability in Oxyallyl Diradicaloids: A Three-State Model Approach

Bis(benzofuranonyl)methanolate (BM4i4i) dye and croconate dyes (derivatives of oxyallyl molecules) in general are known to have intense transitions in the near-infrared (NIR) region, indicating small transition energies and large transition dipole moments. These molecules have been reported in the literature to have very large resonant third-order nonlinear optical (NLO) susceptibilities and molecular hyperpolarizabilities (gamma). In this work we investigate using density functional theory (DFT)/ab initio/symmetry adapted cluster-configuration interaction (SAC-CI) techniques the oxyallyl substructure and attribute the NIR transition and the NLO activity to this substructure, which is common in all these molecules. Using valence bond (VB) theory, an analysis of a three-state model of this substructure is carried out. It is seen that the mixture of an intermediate diradical character and some zwitterionic character in the molecule and a large coupling between these two VB resonance forms is responsible for large gamma values. This can be used as a design principle for increasing NLO activity in oxyallyl derivatives.

Polymorphism, crystal growth and characterization of an organic nonlinear optical material: DAPSH

We have investigated the crystal growth, structural and physical properties of the organic nonlinear optical salt trans-4′-(dimethylamino)-N-phenyl-4-stilbazolium hexafluorophosphate (DAPSH). The chromophore in this recently created material shows a first molecular hyperpolarizability considerably larger than that of the related cation in the well-studied salt DAST (trans-4′-(dimethylamino)-N-methyl-4-stilbazolium tosylate). Through recrystallization of DAPSH using various solvents and conditions we have obtained three different crystalline phases. Phase a of DAPSH has a large second-order nonlinear optical susceptibility χ2. It crystallizes from acetone solutions and grows as purple needles, which are non-centrosymmetric with the space group Cc being suitable for electro-optic applications. Phase b with the triclinic non-polar space group P appears as reddish-brown thin plates when grown from DMSO solutions. It shows large third-order nonlinear optical susceptibility χ3 and can be easily grown as thin films, making it a good candidate for all-optical switching applications. Phase c with the non-polar space group P21/m grows as bright orange plates when crystallized from (50 : 50 vol%) ethanol–acetone solutions. This material shows no significant bulk nonlinear optical activity.

Nonlinear optical properties of an organic film formed of dye aggregates with absorption in the telecommunication wavelength range

An organic film formed of newly synthesized dye aggregates with an absorption peak in telecommunication wavelength range exhibited large third-order nonlinear optical susceptibility χ(3) and fast recovery of bleached absorption. A derivative with a di(benzofuranonyl)methanolate structure forms stable aggregates in a spin-coated film and shows an absorption maximum at 1.24 μm. An imaginary part χI(3) of the film assumes a maximum at 1.30 μm, which is −0.83×10−7 esu. The time evolution of differential transmission spectra indicates that the time constant of the recovery of bleached absorption is 80–240 fs for a fast component and 2.2–6.5 ps for a slow one. This organic film has considerable advantages for future planar optical devices.

2,6-Bis(butylamino)-4,8-dihydroxy-1,5-naphthalenedione

The title compound, C18H24N2O4, is an amino­naphtho­quinone derivative that exhibits a large third-order non-linear optical susceptibility. The centrosymmetric naphtho­quinone moieties are connected by bifurcated N—H⋯O hydrogen bonds to form a ribbon structure along [1\overline10]. The mol­ecules are stacked along the c axis, with overlap occurring only at the periphery of the naphtho­quinone skeleton.

Fe-doped BaTiO3 Thin Films with Large Third-OrderNonlinear Optical Susceptibility

Iron-doped BaTiO3 epitaxial thin films have been fabricated using thepulsed laser deposition technique. The target was an Fe/BaTiO3two-material physical assembly. The films were grown on MgO (100)substrates at 650°C. The crystalline property of the films wasstudied by x-ray diffraction. The result indicated that the Fe-dopedBaTiO3 films did not degrade their crystallinity at the dopantconcentration of 4 mol%. The nonlinear optical properties of the filmswere determined using the z-scan method at the wavelength of 532 nm witha laser duration of 10 ns. The real and imaginary parts of thethird-order nonlinear susceptibility χ(3) were determined to be3.67×10-7 esu and 4.82×10-8 esu, respectively.

Third-order nonlinear optical susceptibility of polymers based on carbazole derivatives

The third-order nonlinear optical susceptibility (χ〈3〉) of poly(N-vinylcarbazole) (PVK) and two other modified polymers based on carbazole derivatives has been measured by degenerate four-wave mixing at 532 nm in a tetrahydrofuran solution. The polymer exhibits large third-order nonlinear optical susceptibility (χ〈3〉) values. The calculated χ〈3〉 value for the copolymer 3-(2-metacryletoxy)carbonyl 7 diethylamin-coumarine (PC1MK), which was obtained by linking 2-(9-carbazolyl)ethyl methacrylate polymer with 3-(2-metacryletoxy)carbonyl 7 diethylamin-coumarine monomer, is approximately 3 times larger than those of poly(3-methoxy-N-vinyl)carbazole and (PVK).

Large Third-Order Nonlinear Optical Susceptibility of Rh-DopedBaTiO3 Thin Films Prepared by Pulsed Laser Deposition

Rh-doped barium titanate (BaTiO3) epitaxial thin films have been fabricated onSrTiO3 (100) substrates by pulsed laser deposition. The nonlinear opticalproperties of the films were determined using the z-scan method at a wavelengthof 532 nm with a laser duration of 10 ns. The real and imaginary parts of thethird-order nonlinear susceptibility χ(3) were 5.71×10-7 esuand 9.59×10-8 esu, respectively. The real part value of χ(3)of the Rh:BaTiO3 films is about one order larger than that ofCe-doped BaTiO3 thin films. The results show that Rh:BaTiO3 thinfilms have great potential applications for nonlinear optical devices.

Third-order optical nonlinearities of near-infrared dyes

Near-infrared dyes – di- and tri-indocarbocyanine dyes and nickel dithiolenes – were synthesized and their third-order optical nonlinearities in solutions were investigated by using the degenerate four-wave mixing technique. Large third-order nonlinear optical susceptibilities with γ values of up to 10 −29 esu were observed. The γ value of the indocarbocyanine dyes increases with increase of conjugation length of the polymethine chain. The central ring structure in the chromophore lowers the γ value of the indocarbocyanine dyes. With change of the substituents on the benzene ring an increase in γ value is observed for all the asymmetric nickel dithiolenes. The order of increase of nonlinear hyperpolarizability is as follows: H<Cl<CH 3<C 2H 5<CH(CH 3) 2.

Novel polydiacetylenes for optical materials: beyond the conventional polydiacetylenes

Polydiacetylenes (PDAs) are of great interest due to their π-conjugated backbone related properties, such as linear and nonlinear optical properties. As a consequence, design and preparation of PDAs assume enormous importance today. This review deals with one aspect of PDA, that is, design and preparation of the diacetylene monomers and their polymers, PDAs having conjugated side groups. The aim of such an investigation is to produce materials which exhibit large third-order nonlinear optical susceptibilities and which consequently, can be obtained in a form to be customised for optical devices.

Photoluminescence, Electroluminescence, Nonlinear Optical, and Humidity Sensitive Properties of Poly(p-diethynylbenzene) Prepared with a Nickel Acetylide Catalyst

The π-conjugated polymer poly(p-diethynylbenzene) (PDEB) has potential applications in electronics and optics; however, its poor solubility and processability have limited its usefulness. The new synthesis reported here makes use of a novel nickel catalyst, and gives rise to PDEB with good solubility and excellent thermal stability characteristics. The polymer exhibits fair photoluminescence and electroluminescence, a large third-order nonlinear optical susceptibility, and good humidity sensitivity, while doped PDEB shows semiconductor characteristics.

Electronic and nuclear contributions to the third-order nonlinear optical susceptibilities of new p-N, N^?-dimethylaniline tetrathiafulvalene derivatives

We report large third-order nonlinear optical susceptibilities (?3?)(ijkl) of new tetrathiafulvalene derivatives, using the degenerate four-wave mixing (DFWM) method. To understand the physical nature of the optical nonlinearities, we separate their electronic and nuclear contributions. The electronic contribution to the third-order nonlinear optical susceptibilities of the molecules turns out to be dominant. From DFWM measurements we also deduce the values of the second-order hyperpolarizabilities gamma, which are ~10(5) greater than the gamma value of CS(2).