Anna Samoc

Dispersion of refractive properties of solvents: Chloroform, toluene, benzene, and carbon disulfide in ultraviolet, visible, and near-infrared

Refractive index dispersion formulas have been derived for chloroform, toluene, benzene, and carbon disulfide from a broad range of the experimental refractive index data at 20 °C. The data were examined with the linear least-squares method. The dispersion equations allow one to calculate the values of refractive index required for analysis of nonlinear optical measurements in the UV, visible, and near-IR wavelength range (0.3–2.5 μm) in these liquids and solutions. The indices were compared to those estimated from quantum chemical calculations. A survey of the experimental data revealed that the measurement results published recently [Opt. Mater. 20, 81 (2002); Rev. Sci. Instrum. 65, 2056 (1994); 66, 38 (1995); 69, 1243 (1998)] were significantly different from other data reported in the literature.

Third-order Optical Nonlinearities of Oligomers, Dendrimers and Polymers Derived from Solution Z-scan Studies

Z-scan measurements provide a simple way of determining and comparing the third-order nonlinear properties of chemical compounds, especially if measurements can be done on solutions in common solvents. We discuss advantages of the solution Z-scan technique, e.g. the possibility of in situ studies of electrochemical switching of third-order nonlinearity, and problems encountered on the interpretation of the results, such as those due to thermal nonlinearity and solvent effects.

Bridged Triphenylamine-Based Dendrimers: Tuning Enhanced Two-Photon Absorption Performance with Locked Molecular Planarity

Triphenylamine derivatives bridged by methylene units afford a near planar molecular platform in a series of one dimer and two oligomers exhibiting increased structural rigidity compared to that of their parent triphenylamines. This series of dendrimers show significantly enhanced two-photon absorptions that are up to 3-fold that of triphenylamines with similar molecular size and structure.

Optical properties of an ormosil system comprising methyl- and phenyl-substituted silica

Abstract We report an organically modified silica (ormosil) system in which the refractive index can be varied from 1.40 to 1.55 by modifying the silica backbone with phenyl and methyl groups, which increase and decrease the refractive index, respectively. By changing the quantities of the phenyl- and methyl-modified precursors in the sol–gel mixture, the refractive index can be varied while keeping the organic fraction of the material constant. Crack-free, dried films up to 15-μm thick have been coated onto silicon and glass substrates, with potential application to optical waveguides for planar integrated circuits. The contributions of SiO–H and C–H absorptions to the attenuation in the communications windows are discussed, along with factors affecting the homogeneity and cracking tendency of the ormosils.

Linear and nonlinear optical properties of a ladder poly(p-phenylene) polymer

Abstract Linear and nonlinear optical properties of a ladder polymer based on the poly(p-phenylene) backbone (LPPP) have been investigated. Femtosecond degenerate four-wave mixing (DFWM) was used for the determination of the nonlinear refractive index n2 at 800 nm. Values of ‖n2‖ = (3–7) × 10−13 cm2/W were obtained from DFWM measurements on thin films and solutions of the polymer. The two-photon absorption coefficient of LPPP is estimated to be β=5×10−9 cm/W at 800 nm.

Combining Very Large Quadratic and Cubic Nonlinear Optical Responses in Extended, Tris-Chelate Metallochromophores with Six π-Conjugated Pyridinium Substituents

We describe a series of nine new complex salts in which electron-rich Ru(II) or Fe(II) centers are connected via pi-conjugated bridges to six electron-accepting N-methyl-/N-arylpyridinium groups. This work builds upon our previous preliminary studies (Coe , B. J. J. Am. Chem. Soc. 2005, 127, 13399-13410; J. Phys. Chem. A 2007, 111, 472-478), with the aims of achieving greatly enhanced NLO properties and also combining large quadratic and cubic effects in potentially redox-switchable molecules. Characterization has involved various techniques, including electronic absorption spectroscopy and cyclic voltammetry. The complexes display intense, visible d --> pi* metal-to-ligand charge-transfer (MLCT) bands, and their pi --> pi* intraligand charge-transfer (ILCT) absorptions in the near-UV region show molar extinction coefficients as high as ca. 3.5 x 10(5) M(-1) cm(-1). Molecular quadratic nonlinear optical (NLO) responses beta have been determined by using hyper-Rayleigh scattering at 800 and 1064 nm and also via Stark (electroabsorption) spectroscopic studies. The directly and indirectly derived beta values are very large, with the Stark-based static first hyperpolarizabilities beta(0) reaching as high as ca. 10(-27) esu, and generally increase on extending the pi-conjugation and enhancing the electron-accepting strength of the ligands. Cubic NLO properties have also been measured by using the Z-scan technique, revealing relatively high two-photon absorption cross sections of up to 2500 GM at 750 nm.

Deoxyribonucleic acid-based photochromic material for fast dynamic holography

The authors acknowledge the Australian Research Council Discovery Project No. DP0556942, the Materials and Manufacturing Directorate Air Force Office of Scientific Research, the AOARD Grant No. 05-4010, and the Polish Ministry of Science and Higher Education Grant No. N50713231/3302 for financial support.

Tuning the properties of poly(p-phenylenevinylene) for use in all-optical switching

We show that, as the conjugation length of poly(p-phenylenevinylene) increases, the ratio of its two-photon absorption coeff icient to third-order nonlinearity at 800 nm decreases, rendering the material suitable for alloptical switching.

Saturable absorption in poly(indenofluorene): A picket-fence polymer

Poly(indenofluorene) shows a strong degenerate four-wave mixing (DFWM) response when it is excited with 100-fs pulses at 800 nm. The DFWM signal scales with the 1.5 power of the input intensity, which we interpret as being due to absorption saturation phenomena. The saturation was studied by open-aperture Z scan in dilute solutions of poly(indenofluorene) in chloroform. The changes in the absorption coefficient alpha are described by the formula alpha = alpha(0)/[1 + (I/I(sat))(1/2)], where I(sat) is the saturation intensity, which is found to be of the order of 100>MW/cm(2).

Photoconductivity of Crystalline Iodoform I.

Abstract Steady state photoconduction in iodoform has been studied between 210–400 nm. The photoconduction threshold is at 345 nm whereas the crystal absorption extends up to 480 nm. The photoconductivity action spectrum shows a steep rise of the photo carrier generation efficiency in the range 345–290 nm and a plateau at shorter wavelengths. Current-voltage characteristics measured under steady illumination show a square dependence of the photocurrent on applied voltage showing the influence of space charge effects. Electron photocurrents are three orders of magnitude lower than hole photocurrents. The lower limit of the photogeneration quantum yield is estimated as 6 × 10−3 charge carriers/photon with an applied field of 1 × 104 V/cm.