Investigation on the chiral recognition mechanism between verteporfin and cholate salts by capillary electrophoresis.

In this article, capillary electrophoresis was applied to investigate the chiral recognition mechanism for the enantioseparation on a well-known second-generation photodynamic therapy drug of benzoporphyrin derivative monoacid ring A, that is, verteporfin. In our previous study, cholate salts have been studied as the chiral selectors, which can realize baseline separation of the four verteporfin isomers. Aiming to reveal the chiral recognition mechanism, the separation effect of several kinds of chiral selectors was discussed. According to the results and references, the chiral separation mechanism of this system was concluded: the analytes selectively combine with the chiral micelles, that is, dynamic H-bonds interactions occur between the hydroxyl groups on the outer side of the cholate micelles and the ester/carboxy groups of the four isomers. In addition, the role of dimethyl formamide as an organic modifier was also researched, including reducing the effective mobility of the analytes and mobility of electroosmotic flow, and preventing them from adsorbing to the capillary wall and self-aggregating of verteporfin, which are pretty beneficial for separation. The method used in this article provides a direct and reliable solution to study the mechanism of chiral separation.

Asterisk-shaped microstructured fiber for an octave coherent supercontinuum in a sub-picosecond region.

We selected two thermally matched silicate glasses with fair refractive index contrast and developed an asterisk-shaped all-solid microstructured optical fiber. The fiber presents a low, ultra-flat, and all-normal dispersion in a wide wavelength range, allowing for the generation of an octave-spanning coherent supercontinuum (SC) in a 20 dB dynamic range with 0.5 ps pump pulses at 1.55 µm. This result improves pump pulse duration that is only ∼100 fs, related to the broadband and highly coherent SC generation in fibers with all-normal dispersion. This enables broadband SC sources with all-fiber, high-power, and highly coherent properties.

Influence of Stark splitting levels on the lasing performance of Yb(3+) in phosphate and fluorophosphate glasses.

Lasing properties have been investigated for Yb(3+) doped glasses with similar emission cross sections (σ(emi)) and lifetime while possessing different Stark levels. Narrow Stark splitting of Yb(3+)-phosphate glass is responsible for severe heat generation, narrow emission band and much smaller σ(emi) at lasing wavelength, making Yb(3+)-phosphate glass unsuccessful to achieve laser output, whereas 1.166W cw laser was obtained in Yb(3+)-fluorophosphate (FP) glass with broader Stark splitting. Analysis on laser system levels reveals that under room temperature, Yb(3+) laser is quasi-3.13-level in phosphate glass and quasi-3.36-level in FP glass. These demonstrations suggest that unless the Stark splitting is enlarged, conventional Yb(3+)-phosphate glass is not a good gain medium for bulk Yb(3+)-laser.

Low threshold mid-infrared supercontinuum generation in short fluoride-chalcogenide multimaterial fibers.

Mid-infrared supercontinuum generation (SCG) is mostly studied in fluoride glass fibers in which long fibers and high power pump sources are needed. Taking advantages of high nonlinearity and transparency, chalcogenide glass is also applied for SCG in mid-infrared region, where specific strategy is needed to compensate large normal material dispersion. We investigate multimaterial fibers (MMFs) combined with fluoride and chalcogenide glasses for SCG. The high refraction contrast allows the zero dispersion point of the fiber to shift to below 2 µm without air holes. These two materials have similar glass transition temperatures and thermal expansion coefficients. They are possible to be drawn together. Both step-index MMFs and microstructured MMFs (MS-MMFs) are considered. The chromatic dispersions and supercontinuum spectra are studied. A 20 dB bandwidth of over one octave SCG with high coherence can be obtained from a 1 cm MS-MMF at 1.95 µm with a pumping peak power of 175 W. As the pump power increased, the spectrum can extend to 5 µm. In this scheme the fiber is so short that the high level of loss, which is the feature of MMFs, will not cause problems.