Second-order Nonlinear Optical Coefficients Research Articles

Synthesis and properties of a ROMP backbone polymer with efficient, laterally appended nonlinear optical chromophores

The synthesis and properties of a new ROMP backbone polymer bearing lateral donor–acceptor-substituted (E)-diethynylethene ((E)-hex-3-ene-1,5-diyne) chromophores are described. The polymer with an average of 40 monomeric repeat units is readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane and chloroform. Good optical-quality films were obtained by spin coating. The third-order susceptibility χ(3) at a wavelength of 1907 nm was determined to be 100 times greater than that of fused silica. After electrical poling, the polymer also showed a significant second-order nonlinear optical coefficient (d33) value, which decays by a factor of two over a period of one month at room temperature.

Size-dependence of the Linear and Nonlinear Optical Properties of GaN Nanoclusters

ABSTRACTIn this paper, we present the results of our first-principles quantum mechanical studies of the electronic structure, geometry, and linear and nonlinear optical (NLO) properties of tetrahedral Gam Nm (m=1, 4, 7, 17) atomic clusters. Our calculated results suggest that the linear and NLO properties both exhibit a strong dependence upon cluster size and shape (geometry). However, the size- and the geometry-dependences are more pronounced for the NLO properties than for the linear optical properties. For clusters containing equal numbers of Ga and N atoms, an open-structure with no network-forming ring has a much larger second-order NLO coefficient than a cluster with a closed ring structure.

Second-order nonlinearity in bulk azodye-doped hybrid inorganic–organic materials by nonresonant all-optical poling

Azodye-doped vinyl group substituted bulk silica materials were prepared by a sol–gel method. Photoinduced noncentrosymmetry in these initially centrosymmetric rigid matrixes was demonstrated first using nonresonant all-optical poling with a fundamental light at wavelength of 1500 nm and its second-harmonic light. The largest photoinduced second-order nonlinear optical coefficient d 33 was estimated to be 8×10 −3 pm/V. The characteristic kinetics of decay of the induced second-order susceptibility was measured by second-harmonic generation. Although the signal decay was fast and the coefficient d 33 was low, we found that increasing the power of the seeding beams could improve the second-harmonic signal decay process.

Design and synthesis of a thermally stable second-order nonlinear optical chromophore and its poled polymers

A multiple charge-transfer second-order nonlinear optical (NLO) chromophore 2,3-bis(4-aminophenyl)-5,6-dicyanopyrazine (BAPDCP) was successfully designed and synthesized. It was characterized by 1H NMR, mass spectrometry, Fourier transform infrared spectroscopy, and elemental analysis. The first hyperpolarizability β of BAPDCP was measured with the Hyper–Rayleigh scattering technique, which was 123.5 × 10−30 esu. The donor-embedded prepolyimide and prepolyurea were also synthesized by a polyaddition reaction. Thermogravimetric analysis and differential scanning calorimetry demonstrated that either the chromophore or the polymers have fine thermal stability. The thin films of prepolymers were prepared by coating on ITO glass substrate and poled by corona poling at elevating temperature. The second-order NLO coefficients d33 of the films were measured by in situ second-harmonic generation measurements. The d33 were deduced as 27.7 and 16.5 pm/V for polyurea and polyimide at 1064 nm fundamental wavelength, respectively. The onset depoling temperature of the polyimide and polyurea were both as high as 200 °C. To understand the temperature effect to the orientation thermal stability of polyimide, two films were treated at different final poling temperatures. The depoling experimental results showed that the orientation stability is higher, as raising the final treated temperature but the d33 value are almost similar. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2846–2853, 2003

A Thermally Stable Chromophore with Multi-intramolecular Charge-transfer and Its Poled Polymer

A new second-order nonlinear optical (NLO) multi-intramolecular charge-transfer chromophore 2,3-bis (4-aminophenyl)-5,6-dicyanopyrazine (DAPDCP) has been designed and synthesized successfully It shows that the maximum absorption wavelength λ max of UV/Vis spectrum in 1,4-dioxane is 423 nm and the melting point is above 300°C. The doped film of it in PMMA was prepared and poled by corona poling with increasing temperature step by step (5°C/min). The second-order nonlinear optical coefficient d 33 is deduced to be 27.2pm/V by the in-situ SHG measurements. The depoling experiments showed that the on-set temperature of the decay of orientation order is 105°C, which is higher than that of the typical NLO chromophore N-(4-nitro phenyl)-(s)-prolinol (NPP) doped in PMMA. It has demonstrated again that the harmony of thermal stable-nonliearility-transparent trade-off can he established by using the designed X-type chromophore with multi-intramolecular charge-transfer.

Constituent chemical bonds and nonlinear optical coefficients of Na 2SeO 4·H 2SeO 3·H 2O molecular crystal

Constituent chemical bonds of Na 2SeO 4·H 2SeO 3·H 2O molecular crystal are studied by the chemical bond method. The valence state of constituent atoms, the chemical bond property of constituent chemical bonds, and the second-order nonlinear optical (NLO) coefficients of Na 2SeO 4·H 2SeO 3·H 2O crystal are quantitatively calculated. Contributions of all kinds of constituent chemical bonds to the total linear and NLO properties of this crystal at λ=871.6 nm have been determined. The hydrogen bonds play a very important role in contributing to the total optical properties of Na 2SeO 4·H 2SeO 3·H 2O crystal, however, the coordination environment of hydrogen bonds strongly affects their optical contributions.

Addendum to: “Optical constant of silicon and silicon dioxide using soft X-ray reflectance measurements”, Pragya Tripathi, G.S. Lodha, M.H. Modi, A.K. Sinha, K.J.S. Sawhney and R.V. Nandedkar Optics Communication 211 (2002) 215–223

The linear optical and second-order nonlinear optical (NLO) properties of an interpenetrating polymer network (IPN) have been investigated. For the poled and cured IPN samples, large second-order NLO coefficients, d33, were measured at 1.064 μm and 1.542 μm. The linear electro-optic coefficients, r33, were determined at various wavelengths. The opled and cured IPN samples showed no measurable decay of the second-order optical nonlinearity after being treated at 110°C for more than 1000 hours. This excellent long-term stability of the NLO property is ascribed to the novel interpenetrating crosslinked molecular structure of the IPN system.

A theoretical study on the second-order nonlinear optical susceptibilities of lithium formate monohydrate crystal, HCOOLi·H2O

Abstract Ab initio calculations of the first hyperpolarizabilities of (HCOOLi·H 2 O) 2 n supermolecules, as the building-blocks of lithium formate monohydrate (LFM) crystal with extended system, were performed for the first time. The dependence of the static β ijk 0 values on chain length was explored, and the frequency dependence of β ijk (−2 ω ; ω , ω ) was measured, and the influences of electron correlation and basis set on β ijk 0 were evaluated. Finally, we predicted the second-order nonlinear optical coefficients of LFM crystal. The β ijk 0 value of (HCOOLi·H 2 O) 2 n is linearly dependent on the chain length of supermolecule, which is quite unusual for an extended system connected by the O–Li bonds with ionic characters. Although the static component of β zzz 0 tensor is the static largest in these three components under study, the absolute value of frequency-dependent β zyy (−2 ω ; ω , ω ) element, transforming the smallest into the largest, is the most sensitive to frequency. After the fundamental wavelength is smaller than 500 nm, it is found that the β ijk (−2 ω ; ω , ω ) value is resonantly enhanced to a great extent due to the double frequency lies in the region of resonance. In addition, the β zxx 0 value goes from negative to positive with changes of electron correlation and basis set. Obviously, it is very necessary to take into account the effect of electron correlation, if the hyperpolarizability tensor components must be accurately calculated. Moreover, it is also very important whether it is adopted a complete basis set with diffuse and polarization functions. The calculated nonlinear coefficients at high level suggest that the scaled set reported by Robert seem more reasonable.

Crystallographic modifications of physical properties of lithium niobate crystals by the cation location

On the basis of crystallographic data of various pure and doped lithium niobate crystals, Pauling's rules, the bond valence sum model and the chemical bond method are employed to understand crystallographic modifications of physical properties of lithium niobate crystals. The physical properties such as dielectric responses (including the principal refractive indices and second-order nonlinear optical coefficients), the spontaneous polarization and the spontaneous strain are quantitatively or qualitatively studied. The present work shows that the vacant site in the lithium niobate crystallographic frame constructs a useful buffer for Li + and Nb 5+ cations to balance their strong interaction, which is not energetically available for any cation; the Nb 5+-site can give a strong effect on the mechanical properties of crystals, which is tremendously important for the crystal growth; the Li +-site is closely correlated to the dielectric properties of crystals, which is an active and sensitive lattice site available for various dopants with the valence ranging from +1 to +5.

Theoretical studies on hyperpolarizabilities and UV-vis-IR spectra of a diamminecobalt(iii) tetripeptide transition-metal complex

The second-order polarizabilities and the UV-vis-IR spectra of a transition-metal complex Co(NH3)2(L-ala–gly–gly) have been studied by using the MP2 and TDHF methods. The complex has a maximum β component in the direction from the N(alanyl) group to the N(glycyl) groups. A transparent optical spectrum region from 0.55 to 5.5 µm was found, which offers potential applications as an optical material. The alkyl substitution of the glycyl group only slightly affected the β value and retained the IR transparent region but may cause the molecules to have a favorite packing fashion in the bulk crystal that leads to larger second-order nonlinear optical coefficients.

Domain switching characteristics and fabrication of periodically poled potassium niobate for second-harmonic generation

We report on the 180° domain switching characteristics and fabrication of periodically poled KNbO3 for second-harmonic generation. Using a modified triangular pulse, a periodically poled KNbO3 of very high quality was fabricated with dimensions of 3×4×0.925 (a×b×c) mm3 and a period of 32.5 μm to utilize the d31 component of the second-order nonlinear optical coefficient tensor. An efficient second-harmonic generation of a mode-locked Nd:YAG laser, operated at 1064 nm with a pulse width of 35 ps, was achieved with a maximum conversion efficiency of 34.8%. The effective nonlinear coefficient, measured in the limit of undepleted pump approximation, was 5.2 pm/V, which is 68% of the theoretical value.

Optimization and characterization of the guest-host polyetherketone polymer films for application in integrated optical devices

In order to optimize the loading of 3-(1,1-dicyanothenyl)-1-phenyl-4, 5-dihydro-1H-pryazole (DCNP) in polyetherketone (PEK-c) guest-host polymer films, ten kinds of DCNP/PEK-c thin films, in which the weight per cent of DCNP changes from 5 to 50, were prepared. Their second-order nonlinear optical coefficients χ33(2) at λ = 1064 nm were measured by using Maker fringe method after poling under the optimal poling condition. Their optical waveguide transmission losses were measured at 632.8 nm. Optimal weight per cent of the chromophore for the DCNP/PEK-c guest-host polymer system has been determined as about 20 for use in the integrated optical devices.

Synthesis of Polymers Bearing Oligo‐Aromatic Esters for Second‐Order Nonlinear Optics

We synthesized methacrylate-type polymers bearing oligo-aromatic esters as side chains to create unique second-order nonlinear optical (NLO) active polymers (PMAn-x, PMAnC-x, PMA2N-x, and PBA3N-x, x = oligo-aromatic ester contents) for the investigation of the resulting architecture. The polymers were obtained from the polymerization of methacrylated oligo-aromatic esters and the copolymerization of the esters with methyl methacrylate or tert-butyl methacrylate using a radical initiator. The cut-off wavelength (λ co ) of these polymers was shorter than the visible region aimed at, i.e. λ co = ca. 330-370 nm, which is much shorter than λ co of the typical second-order NLO polymers containing groups such as azobenzene chromophores. Second-harmonic generation (SHG) measurements of these polymer films after treatment by corona poling were carried out using the Makerfringe method. These polymer films exhibited good transparency in the visible region and a second-order nonlinear optical coefficient d 33 of 2.2-9.8 pm.V -1 . The d 33 values of some derivatives decreased with an increase of the chromophore content, which is due to a strong interaction between the side chains with increasing chromophore content.

Side radical influence on the nonlinear optical properties and thermal stability of poled polymer films

Films of polyetherketone doped with the chromophores Disperse Red 1 (DR1) and Disperse Red 13 (DR13) were prepared by spin-coating method. By the in situ Second-harmonic Generation (SHG) signal intensity measurement, the optimal poling temperatures were obtained. For the investigated polyetherketone polymer doped with DR1 (DR1/PEK-c) and polyetherketone polymer doped with DR13 (DR13/PEK-c) films, the optimal poling temperatures were 150°C and 140°C, respectively. Under the optimal poling conditions, the high second-order nonlinear optical coefficient χ33(2) = 11.02 pm/V has been obtained for the DR1/PEK-c; and for DR13/PEK-c at the same conditions the coefficient is 17.9 pm/V. The SHG signal intensity DR1/PEK-c could maintain more than 80% of its initial value when the temperature was under 100°C, and the SHG signal intensity of the DR13/PEK-c could maintain more than 80% of its initial value when the temperature was under 135°C.

Dispersion of second-order nonlinear optical coefficient

A simple, approximate relation between the dispersion of the second-order nonlinear optical (SNLO) coefficient and first-order susceptibility has been derived using the well-known results of density-matrix calculation of quantum-mechanical theory. A new tensor of SNLO coefficient has been defined, which retains symmetries when the input beams are in the spectral range of transparency while the generated beam can also be in the spectral range of absorption. The validity of the relation has been checked for three ferroelectric crystals, KTP, LiNbO3 and KNbO3, which are transparent in the visible and near infrared, and for two semiconductors, GaP and GaAs, which absorb in the visible. Contrary to Miller’s law, the presented relation is in good agreement with measurements.

Effective Second-Order Nonlinear Optical Coefficient of a Novel Transparent Material: N,N-Diphenyl-8-[2-(4-pyridyl)ethenyl]dibenzofuran-2-ylamine

Abstract N,N-Diphenyl-8-[2-(4-pyridyl)ethenyl]dibenzofuran-2-ylamine (1) has been synthesized and its second-order nonlinear optical coefficient has been examined by means of Second Harmonic Wave Generated with the Evanescent Wave (SHEW) method. As a result, 1 has been found to exhibit an effective d coefficient 3.0 times as large as that of urea. The cutoff wavelength of the compound was estimated to be 370 nm.

Synthesis and Characterization of Hyperbranched Polymer for Second-Order Nonlinear Optics

A new hyperbranched polymer was prepared by the one-pot Knoevenagel polycondensation of 4-[N,N-bis(hydroxyethyl)amino−4′ -formyl]-azobenzene (CHO-DOH) with cyanoacetic acid using 4-(dimethylamino)pyridine (DMAP) as a base in tetrahydrofuran (THF). This polymer was soluble in polar aprotic solvents such as N,N-dimethylformamide and dimethyl sulfoxide. The glass transition temperature (T 8 ) of the polymer was observed at 145°C for PE-Azo/Hyper. The second harmonic generation (SHG) measurements of the obtained polymer were carried out by the Maker fringe method after corona poling at 7 kV near T 8 for 10 minutes. The second-order nonlinear optical coefficient, d33 was about 15 pm/V for PE-Azo/Hyper.

Determination of ionic and pure electronic contributions to the electro-optic coefficient of cadmium telluride and gallium arsenide single crystals

High electro-optic figure of merit n 0 3 r 41 and the absence of natural birefringence make semi-insulating gallium arsenide (GaAs) and cadmium telluride (CdTe) attractive materials for the fabrication of electro-optical devices. In this context we characterized both acoustic and optical phonon contributions to the electro-optic coefficient of CdTe and GaAs. Accurate measurements of n 0 3 r 41 as a function of modulation frequency and temperature were carried out on CdTe:In and GaAs crystal at 1.5 μm. For CdTe, to the best of our knowledge, this is the first time that a contribution to the electro-optic coefficient due to optical phonons has been determined. A positive value for the ionic contribution, due to optical phonons in GaAs, is obtained, in disagreement with that previously inferred from Raman scattering efficiency measurements. The pure electronic contribution was then isolated, and the second-order non-linear optical coefficient was derived. The latter was compared to previously reported data from non-linear wavelength conversion measurements.

Efficient near-IR second harmonic generation in II–VI semiconductors

We have measured the absolute value of the second-order non-linear optical coefficient ( d 41) at λ=1.5 μm in the bulk wide-bandgap II–VI semiconductors ZnTe, Cd 0.8Zn 0.2Te, and Cd 0.78Mn 0.22Te, by evaluating the second harmonic generation (SHG) efficiency using a femtosecond laser source in a spectral Maker-like fringes technique. Values d 41=59 pm/V, d 41=78 pm/V and d 41=71 pm/V have been obtained, respectively for ZnTe, CdZnTe, and CdMnTe. High non-linearity and transparency of the ternary alloys characterize them as promising materials for operation in the spectral range for optical communications.

Absolute measurement of second-order nonlinear-optical coefficients of CsLiB_6O_10 for visible- to-ultraviolet second-harmonic wavelengths

The second-order nonlinear-optical coefficients of CsLiB6O10 have been absolutely determined for visible-to-ultraviolet second-harmonic wavelengths. The measurements were made by use of the wedge technique at the fundamental wavelengths of 0.532, 0.852, and 1.064 µm. The following values were obtained: d36=0.92 pm/V at 0.532 µm, d36=0.83 pm/V and d14=0.69 pm/V at 0.852 µm, and d36=0.74 pm/V at 1.064 µm.