Duoyuan Wang

Third- and fifth-order optical nonlinearities in a new stilbazolium derivative

The third- and fifth-order optical nonlinear properties of a new stilbazolium derivative, trans-1-[p-(p-dimethylaminobenzyl-azo)-benzyl]-2-(N-methyl-4-pyridinium)-ethene iodide (DABAZO-PEI), were investigated with a Q-switched and mode-locked pulse laser with a duration of 35 ps at 1064 nm. Its linear optical properties were also discussed. DABAZO-PEI exhibits two-photon absorption and strong excited-state absorption induced by two-photon absorption. A positive third-order nonlinear refraction caused by bound electrons and negative excited-state refraction caused by the two-photon absorption-generated excited states were also observed. The magnitude and the sign of the real (refractive) and the imaginary (two-photon absorption) parts of the molecular third-order polarizability, and the excited-state absorption and refraction cross sections, were measured. A feature worth noting is the values of excited-state absorption and refraction cross sections. They are all as high as 10-17xa0cm2. Based on the excited-state absorption induced by the two-photon-absorption mechanism, a highly efficient optical-limiting behavior for incident fluence in the range of 0–10 J/cm2 was demonstrated in a 1-cm-path quartz cell containing DABAZO-PEI solution in dimethyl sulfoxide. The optical-limiting threshold was estimated to be as low as 5 mJ/cm2.

Isolation of Y- and X-linked SCAR markers in yellow catfish and application in the production of all-male populations

Sex controls have been performed in some farmed fish species because of significant growth differences between females and males. In yellow catfish (Pelteobagrus fulvidraco), adult males are three times larger than female adults. In this study, six Y- and X-linked amplified fragment length polymorphism fragments were screened by sex-genotype pool bulked segregant analysis and individual screening. Interestingly, sequence analysis identified two pairs of allelic genes, Pf33 and Pf62. Furthermore, the cloned flanking sequences revealed several Y- and X-specific polymorphisms, and four Y-linked or X-linked sequence characterized amplified region (SCAR) primer pairs were designed and converted into Y- and X-linked SCAR markers. Consequently, these markers were successfully used to identify genetic sex and YY super-males, and applied to all-male population production. Thus, we developed a novel and simple technique to help commercial production of YY super-males and all-male populations in the yellow catfish.

A linkage map of common carp (Cyprinus carpio) based on AFLP and microsatellite markers.

Common carp (Cyprinus carpio) is an important fish for aquaculture, but genomics of this species is still in its infancy. In this study, a linkage map of common carp based on Amplified Fragment Length Polymorphism (AFLP) and microsatellite (SSR) markers has been generated using gynogenetic haploids. Of 926 markers genotyped, 151 (149 AFLPs, two SSRs) were distorted and eliminated from the linkage analyses. A total of 699 AFLP and 20 microsatellite (SSR) markers were assigned to the map, which comprised 64 linkage groups and covered 5506.9 cM Kosambi, with an average interval distance of 7.66 cM Kosambi. The normality tests on interval map distances showed a non-normal marker distribution. Visual inspection of the map distance distribution histogram showed a cluster of interval map distances on the left side of the chart, which suggested the occurrence of AFLP marker clusters. On the other hand, the lack of an obvious cluster on the right side showed that there were a few big gaps which need more markers to bridge. The correlation analysis showed a highly significant relatedness between the length of linkage group and the number of markers, indicating that the AFLP markers in this map were randomly distributed among different linkage groups. This study is helpful for research into the common carp genome and for further studies of genetics and marker-assisted breeding in this species.

Optical limiting performances of asymmetric pentaazadentate porphyrin-like cadmium complexes

The optical limiting performances of seven asymmetric pentaazadentate porphyrin-like cadmium complexes have been measured at 532 nm with nanosecond pulses. In a f/38 geometry, with sample transmission of 0.51–0.80 in a 2 mm cell, the limiting thresholds for these complexes were 1.4–3.0u2009mJ/cm2. The throughputs of these complexes were limited to 0.31–1.13u2009J/cm2 for incident fluences as high as 3.5u2009J/cm2. The limiting throughput was strongly influenced by the nature of the ligand. Lower bounds for the ratio of triplet excited-state to ground-state absorption cross sections have been estimated at 3.4–5.7. The lower limiting thresholds, lower limiting throughputs, as well as the ease of modification of the ligands, make these complexes promising candidates for optical power limiters.

Nonlinear excited state absorption in cadmium texaphyrin solution

Nonlinear absorption at 532 nm in a cadmium texaphyrin solution has been studied using 8 ns and 23 ps laser pulses. The experiments show that reverse saturable absorption occurs in the nanosecond case. For picosecond pulses, reverse saturable absorption occurs only at low fluences, and the transmission increases with increasing incident fluence at high fluences. A six‐level model is presented to explain these nonlinear absorption effects. Several photophysical parameters for cadmium texaphyrin, such as absorption cross sections at 532 nm and lifetimes, have been evaluated by theoretical simulations of the experimental results.

Characterization and sources of regional-scale transported carbonaceous and dust aerosols from different pathways in coastal and sandy land areas of China

[1]xa0Concentrations of 12-hour averaged organic carbon (OC), elemental carbon (EC), and other trace elements were determined from bulk aerosol samples at a coastal city of Lian Yun Gang (LYG) in east China from June to December 2003 and a sandy land site of Tong Liao in northeast China from June to August 2003. Regional transports from four main source areas accounted for ∼35–49% of the Asian dust and 16–18% of the carbonaceous particles for both sites. The regional mean concentrations of various species, especially EC, were comparable to or lower than those in urban areas of inland China, Korea, and Japan but tended to be higher than those in Hong Kong or rural sites in east Asia. At LYG, OC showed a clear seasonal pattern with a peak loading in winter (24 μg m−3) and a low in summer (10 μg m−3). Seasonality of EC was more pronounced than that of OC with a difference of approximately threefold (3.8 to 11 μg m−3). Three types of air masses with high particulate loadings were found to be responsible for the peak EC and low OC/EC ratios in winter. Clean air masses with more than 50% secondary organic carbon contents were largely of marine origins. Elemental concentrations (Ca, Fe, K, Mn, and Ti) were mainly associated with Asian dust aerosols with a certain fraction of K from biomass burning in mainland China characterized with a ratio of 1.3 for OC/K.

Nonlinear dependence of solvent polarity effects on twisted intramolecular charge-transfer states and linear relation for electronic spectra in a stilbazolium-like dye

Abstract The photophysical properties of a stilbazolium-like dye, trans -1-( N -methylpyrrol-2-yl)-2-( N -methyl-4-pyridinium)-ethene iodide, in 20 solvents and its photochemistry were investigated. A division into two groups in the linear relation between the solvatochromic shifts (absorption, fluorescence emission and corresponding Stokes shifts) and solvent polarity parameter E T N was observed. The dipole moments of fluorescence emission and twisted intramolecular charge-transfer state were estimated. The quantum yields of fluorescence and trans → cis photoisomerization change by almost two orders of magnitude. The rate constant of radiative decay is in the order of 10 7 –10 8 xa0s −1 , which is about one or two orders of magnitude less than that of the photochemistry decay, whereas the rate constant of the radiationless decay is in the order of 10 8 –10 10 xa0s −1 . The nonlinear dependence and division into two groups which differs very much from that in the above linear relation were also observed for the solvent polarity influences on the properties of the twisted intramolecular charge-transfer state. The decay scheme from the excited singlet state was assigned as controlled by the equilibrium constant for interconversion between the twisted and planar conformations, which differs from that of reported organic molecules, such as ordinary stilbazolium dyes, stilbene derivatives, or rhodamine B, etc.

Degenerate four-wave mixing and Z-scan measurements of stilbazolium derivatives

Stilbazolium derivatives are very attractive optical materials for photonics and biophotonics applications because a large number of these derivatives are available and they can exhibit large third-order nonlinear coefficients and rapid responses. To quantitatively characterize their third-order nonlinear coefficients and the temporal responses of their third-order nonlinear process, we have performed degenerate four-wave mixing and Z-scan experiments on four stilbazolium derivatives with different electron donors using 40 ps laser pulses at 532 nm. The γ values for three of the compounds are on the order of 10−31u200aesu. These high values arise from electronic processes and are associated with both nonlinear absorption and nonlinear refraction. The relative contributions from nonlinear absorption and nonlinear refraction are dependent on the chemical structure and linear absorption of the stilbazolium derivative.

The high fifth-order nonlinearity in a new stilbazolium derivative: trans-1-[p-(p-dimethylaminobenzyl-azo)-benzyl]-2-(N-methyl-4-pyridinium)-ethene iodide

The third- and fifth-order optical nonlinearities from the titled molecule were investigated using Z-scan technique. The titled molecule exhibits two-photon absorption (2PA) and 2PA-generated excited-state absorption (ESA). A very interesting feature is that the titled molecule shows a high fifth-order nonlinearity, being about one-order of magnitude larger than the reported organic molecules. Due to this strong ESA, a highly efficient optical limiting effect was observed.

Large optical power limiting induced by three-photon absorption of two stilbazolium-like dyes

Three-photon absorption (3PA) of two stilbazolium-like dyes containing conjugated triple bridge (abbreviated as APAI and PPAI) has been determined by using a Q-switched Nd:YAG laser pumped with 35 ps pulses at 1064 nm in DMSO. Nonlinear absorption coefficients alpha(3) derived from 3PA fitting curves are 4.3 and 3.2 x 10(-21) cm(3)/W-2, respectively. Large optical power limiting induced by 3PA has also been demonstrated for both dyes. When the maximum incident irradiance reaches to 400 GW/cm(2), the limiting nonlinear transmissions T-lim can reach to 13 and 17% with maximum transmitted radiances of 17 and 44 GW/cm(2), respectively