Enhancement of the response time in organic photorefractive composites using alkoxy-substituted PDCST as a nonlinear optical chromophore: publisher's note.

This publisher's note contains corrections to Opt. Lett.45, 6767 (2020)OPLEDP0146-959210.1364/OL.409743.

Enhancement of the response time in organic photorefractive composites using alkoxy-substituted PDCST as a nonlinear optical chromophore.

The ease of the molecular orientation of a chromophore has an important effect on the electro-optical (EO) properties of polymeric photorefractive (PR) composites. A derivative of 4-piperidinobenzylidene-malononitrile (PDCST) with an alkoxy group added as a side branch was synthesized to improve the molecular orientation characteristics. Electrophoresis was performed on the polymeric PR composite to which the improved PDCST had been added. The optical properties and response times were examined to evaluate the effects of the substitution of the alkoxy group. PDCST substituted with the alkoxy group showed enhanced EO properties and a PR grating formation rate.

Enhanced photorefractive performance of polymeric composites through surface plasmon effects of gold nanoparticles.

We investigated the photorefractivity enhancement of polymeric composites by introducing gold nanoparticles (NPs). The gold NPs enhance the photocharge generation rate of sensitizers through plasmon resonance coupling achieved between NPs and sensitizers. Systematic studies show that the presence of gold NPs has increased photocharge generation efficiency, photoconductivity, diffraction efficiency, refractive index modulation, and photorefractive (PR) grating formation rate. The gold-NP-doped PR sample exhibits 2 times larger photocharge generation efficiency and photoconductivity, and 2.5 times faster PR grating formation rate compared to the control sample without the NPs.

Promising ZnO-based DSSC performance using HMP molecular dyes of high extinction coefficients.

Employing newly synthesized di-substituted tri-phenyl amine (HMP-9) and carbazole (HMP-11) dyes (with limited acidic carboxyl anchor groups), a power conversion efficiency as high as 7.03% in ZnO nanocrystallite (NC)-based dye-sensitized solar cells (DSSCs) is achieved. The specific molecular designs of HMP-09 and HMP-11 consisting of with and without hexyloxy spacer groups, and added tri-phenyl amine or 9-phenyl-9H-carbazole donor groups, respectively, attached on the ancillary ligands are advantageous, evidenced from electrochemical impedance spectroscopy measurements, for ZnO NC-based DSSCs.

A simple method for fabricating a Mach-Zehnder type waveguide using sol-gel derived photopatternable hybrid materials for optical biosensors.

In this work, we report on a simple method to fabricate a Mach-Zehnder type waveguide pattern using photopatternable sol-gel organic-inorganic hybrid materials. The refractive indices and propagation losses of the gel films were measured using the prism coupling method. The refractive indices of the resulting films were significantly influenced by the 3-trimethoxysilylpropylmethacrylate (TMSPM) concentration, and the average propagation loss was 0.32-0.52 dB/cm at the wavelength of 632.8 nm. The waveguides were fabricated using spin-coating and a photolithography technique. The Y-branch and straight pattern of the Mach-Zehnder waveguide were well-defined and had high transparency (> 97%) in the visible region. The average thickness of the gel films was 10 microm, and the average width of the Mach-Zehnder pattern was 10 microm. The structural and optical properties of the fabricated patterns were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), near-infrared (IR) spectroscopy, and ultraviolet (UV)-visible spectroscopy.

Influence of donor moiety in ruthenium sensitizers on the properties of dye-sensitized solar cells.

Heteroleptic ruthenium complexes cis-[Ru(H2dcbpy)(L)(NCS)2], where H2dcbpy is 4,4'-dicarboxylic acid-2,2'-bipyridine and L is 4-(4-(N,N-di-(p-hexyloxyphenyl)-amino)styryl)-4'-methyl-2,2'-bipyridine (Rut-A) or 4-(4'-(3,6-dihexyloxycarbazole-9-yl)-styryl)-4'-methyl-2,2'-bipyridine (Rut-B), have been synthesized and characterized by NMR, UV-Vis spectroscopy, and cyclic voltammogram. The effect of different electron donors on the properties of dye-sensitized solar cells has been studied. The power conversion efficiency of DSSC based on Rut-B is 6.1% while Rut-A delivered a lower efficiency of 4.52% under the same device fabrication and measuring conditions. The better photovoltaic performance of Rut-B is mainly associated with enhanced dye absorptivity and charge recombination suppression.

Tunable color filter with surface plasmon resonance using organic photorefractive composite.

We report on a tunable color filter with surface plasmon resonance (SPR), excited by a photorefractive (PR) diffraction grating. When a white light was incident at the diffraction grating formed by a PR effect, the SPR generated at a metal-dielectric material interface was absorbed, and the reflected light showed a complementary color. When the period of the PR diffraction grating was modified by alteration of the optic configuration, the wavelength at which the SPR excitation led to a reflection minimum changed and the spectrum of the reflected light also changed. A well-known equation was used to help us understand the experimental results. All experimental results are in good agreement with the calculation predictions. This result could lead to a new type of tunable color filter.

The effect of trap density on the space charge formation in polymeric photorefractive composites.

The effect of trap density on the space charge formation of polymeric photorefractive (PR) composites was studied using the modified Schildkraut differential equation. The densities of electrons, holes, and traps, as well as the rates of generation, recombination, trapping, and detrapping are examined. The steady-state and temporal behaviors of photocurrent and space charge field (E(sc)) formation dependence on the trap density are also discussed. The charge transport dynamics influenced by the presence of the trap molecules controls the formation of E(sc) via charge trapping, charge detrapping, and charge recombination. Experimental studies of photocurrent and E(sc) in poly[methyl-3-(9-carbazolyl) propylsiloxane]-based polymeric PR composites were carried out to demonstrate the applicability of the model.

Temperature dependence on the grating formation in a low-Tg polymeric photorefractive composite.

We investigated a dependence of the grating formation on the temperature in polymeric photorefractive (PR) composite, in terms of magnitude and buildup speed of the PR grating. For polymeric PR materials, the temperature is one of the most important factors together with the external electric field because it is closely related on photocharge generation efficiency, mobility of generated carrier, electro-optic coefficient tensor, and so on. Above the glass transition temperature, the diffraction efficiency of degenerate four-wave mixing decreased with increasing the temperature; it can be explained with the magnitude of space-charge field and the electro-optic behavior at different temperatures. The space-charge field decreased linearly with increasing temperature due to a decrease in the photocharge generation efficiency and an increase in the hole detrapping by the high dark conductivity. Also as we expected, the PR grating buildup speed, which is strongly dependent on the photoconductivity, steeply decreased with increasing the temperature, and its tendency was similar to the temperature dependence of the phase shift.

Metal filament growth in electrically conductive polymers for nonvolatile memory application.

Solution processable polymers that can reproducibly form metal filament by applying voltage are investigated for nonvolatile memory application. Up to present, the understanding of materials enabling to make the metal filament has not been well-documented and the vacuum deposition methods were dominantly used in device fabrication. After screening various polymers, we found that only the polymers having two functionalities, the presence of strongly coordinating heteroatom (S or N) with metal ions and the electrical conductivity, showed the reproducible filament formation behavior. Among the polymers screened, the regiorandom poly(3-hexylthiophene) showed the best switching endurance over 30,000 write-read-erase-read cycles without any switching failure.

Spectral range optimization for the near-infrared quantitative analysis of petrochemical and petroleum products: naphtha and gasoline.

The proper selection of the spectral range in partial least squares (PLS) calibration is critical when highly overlapping spectra from compositionally complex samples are used, such as naphtha and gasoline. In particular, the relevant spectral information related to a given property is frequently localized in a narrow range, and the most selective region may be difficult to locate. We have presented the importance of range optimization in near-infrared (NIR) spectroscopy for the analyses of petrochemical and petroleum products that are generally highly complex in composition. For this purpose, the determination of a detailed compositional analysis (so called PIONA) and the distillation temperature of naphtha were evaluated. In the same fashion, the research octane number (RON) and Reid vapor pressure (RVP) were selected for gasoline. By optimizing the range using moving window (MW) PLS, the overall calibration performance was improved by finding the optimal spectral range for each property. In particular, for a detailed compositional analysis of naphtha, it was effective to search for localized spectral information in a relatively narrow range with fewer factors.

Gold-catalyzed cycloisomerization of o-alkynylbenzaldehydes with a pendant unsaturated bond: [3 + 2] cycloaddition of gold-bound 1,3-dipolar species with dipolarophiles.

[reaction: see text] A new and novel Au-catalyzed cycloisomerization of ynals bearing a pendant unsaturated bond leading to synthetically valuable [6.7.n]-tricyclic compounds were developed. This study strongly supports the intermediacy of [3 + 2] cycloaddition proposed by DFT calculation and provides an easy access to key skeletons found in a variety of natural products.

Highly efficient [2 + 2] intramolecular cyclizations of allenynes under microwave irradiation: construction of fused bicyclic compounds.

A palladium [2 + 2] cycloaddition of 1,6- and 1,7-allenyne carboxylates and microwave-mediated [2 + 2] cycloaddition of various 1,n-allenynes were developed and, particularly, the microwave irradiated [2 + 2] cycloaddition of allenynes can provide a simple, general and eco-friendly synthetic method to fused bicyclo[m,2,0]alkadienes.

Determination of the space-charge field amplitude in polymeric photorefractive polymers.

The space-charge field built in a polymeric photorefractive polymer was calculated by a simple method based on the oriented gas model. When anisotropic chromophores in a photorefractive polymer were exposed to an external field, they oriented preferentially to exhibit a birefringence. Then, under illumination of two coherent beams and an external field, they reoriented to form a photorefractive grating. During the formation of the grating, the chromophores were reoriented by the space-charge field as well as by the external applied field. The birefringence induced in the material by an external electric field was determined by measuring the transmittance of the sample which is placed between crossed polarizers, where birefringence depicts the orientation of the chromophores. By measuring the diffraction efficiency with a modified degenerate four-wave mixing setup, the index amplitude of the grating was determined. Finally, the space-charge field was determined by comparing the diffraction efficiency with the birefringence with respect to the applied electric field. In our study, the space-charge field was about 20% of the external applied field, which coincided with previous results obtained from our laboratory.

Simple method for determining the gain coefficient of a photorefractive polymer film.

We propose a simple method for measuring the gain coefficient of two-beam coupling for photorefractive polymer film. To measure the gain coefficient, we attached a phase grating onto the photorefractive polymer film and made an interference pattern between the transmitted and diffracted beams in the photorefractive film by using an illuminating single beam. The gain coefficient values measured at various external fields by our method showed good agreement with those measured by a standard two-beam coupling method. Compared to standard two-beam coupling, this method exhibited fairly improved stability of the output signal to external factors such as human sounds and airstreams.

Dependence of the Bragg condition on an external electric field for a polymeric photorefractive material.

We investigated the effect of an applied electric field on the Bragg condition of degenerate four-wave mixing a polymeric photorefractive material with a low glass-transition temperatue. For a polymeric photorefractive material the application of an external electric field is necessary for photorefractivity leads to birefringence of the material by poling of the nonlinear optical chromophore. Because the propagation vectors of the pumping and reading beams inside the material are influenced by the refractive index of the material, the Bragg condition depends on the magnitude of the external field. Using an oriented gas model and the-coupled-mode theory, we numerically analyzed the Bragg-mismatch effect that causes a reduction in diffraction efficiency as a function of an external field. We present the boundary conditions for sample thickness and grating spacing for which the Bragg-mismatch effect must be taken into account.