Q. P. Wang

Comparison of c-Nd:YVO4/YVO4 raman lasers and c-Nd:YVO4 self-Raman lasers

Raman lasers based on c-Nd:YVO4 crystals can generate 1178 nm Stokes line, which can be frequency-doubled to realize 589 nm sodium lasers. We make comparative experimental studies of c-Nd:YVO4/YVO4 Raman lasers and c-Nd:YVO4 self-Raman lasers. About these two kinds of lasers, the output characteristics of power, center wavelength and beam quality are measured and compared.

Morphology and chirality controlled self-assembled nanostructures of porphyrin–pentapeptide conjugate: effect of the peptide secondary conformation

An optically active porphyrin–pentapeptide conjugate 1, actually a porphyrinato zinc complex covalently linked with a glycinyl–alanyl–glycinyl–alanyl–glycine (GAGAG) peptide chain, was designed and synthesized. The self-assembly properties of this novel porphyrin–pentapeptide conjugate in THF/n-hexane and THF/water were comparatively investigated by electronic absorption, circular dichroism (CD), IR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) technique. Associated with the different secondary conformation of the pentapeptide chain covalently linked to the porphyrin ring in different solvent systems, self-assembly of conjugate 1 leads to the formation of nanofibers with right-handed helical arrangement and nanotubes with left-handed helical arrangement in a stack of porphyrin chromophores according to the CD spectroscopic result in apolar THF/n-hexane (1 : 3) and polar THF/water (1 : 3) system depending on the cooperation between intramolecular or intermolecular hydrogen bonding interaction with chiral discrimination between pentapeptide chains and porphyrin–porphyrin interactions in the direction parallel to the tetrapyrrole ring of neighboring conjugate molecules. IR spectroscopic result clearly reveals the α-helix and β-sheet secondary conformation, respectively, employed by the pentapeptide chain attached at the porphyrin core in the nanostructures formed in THF/n-hexane (1 : 3) and THF/water (1 : 3). The X-ray diffraction (XRD) result confirms that in the nanotubes, a dimeric supramolecular bilayer structure was formed through an intermolecular hydrogen bonding interaction between two conjugate molecules which, as the building block, self-assembles into the target nanostructures. These results clearly reveal the effect of a secondary conformation of pentapeptide chain in the conjugate molecule on the packing mode of porphyrin chromophore, supramolecular chirality, and morphology of the self-assembled nanostructure. The present result represents not only the first example of organic nanostructures self-assembled from a covalently linked porphyrin–pentapeptide conjugate, but more importantly the first effort towards controlling and tuning the morphology and in particular the supramolecular chirality of porphyrin nanostructures via tuning the secondary conformation of peptides in different solvent systems, which is helpful towards understanding, designing, preparing, and mimicking the structure and role of naturally occurring porphyrin–peptide conjugates. In addition, both nanofibers and nanotubes were revealed to show good semiconducting properties.

Directly LD-pumped passively Q-switched YVO4-Nd:YVO4 laser at 1.34 μm with a V3+: YAG saturable absorber

The performance of a directly LD-pumped passively Q-switched YVO4-Nd:YVO4 laser at 1.34 μm with a V3+:YAG saturable absorber was demonstrated for the first time to the best of our knowledge. The average output power of 580 mW was obtained at the pump power of 8.8 W, corresponding to the optical conversion efficiency of 6.6% and slope efficiency of 11%. The minimum pulse width was 280 ns with the pulse repetition rate of 230 kHz, which was attained with a T = 5.6% output coupler at the pump power of 8.8 W.

Helical nano-structures self-assembled from dimethylaminoethyloxy-containing unsymmetrical octakis-substituted phthalocyanine derivatives

The self-assembling properties of metal free unsymmetrical 2,3,9,10,16,17,23-heptakis(butyloxy)-24-mono(dimethylaminoethyloxy)phthalocyanine H2{Pc(OC4H9)7[OC2H4N(CH3)2]} (1) and its zinc complex counterpart Zn{Pc(OC4H9)7[OC2H4N(CH3)2]} (2) in MeOH have been comparatively investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) technique, and IR and UV-vis spectroscopy. Cooperation of the intermolecular hydrogen bonding/Zn–N coordination bonding with π–π interaction between neighboring phthalocyanine molecules due to the presence of one peripheral dimethylaminoethyloxy side chain for 1 and 2 results in nanostructures with different morphology including left- and right-handed helical ribbons, as well as hollow nanotubes for 1 and nanowire bundles for 2. Electronic absorption spectroscopic results reveal the H-aggregate nature in all the nanostructures formed from both compounds 1 and 2, indicating the dominant π–π inter-molecular interaction between phthalocyanine molecules. The IR and X-ray diffraction (XRD) results reveal a dimeric supramolecular structure formed through the intermolecular hydrogen bonding or Zn–N coordination bonding interaction between two molecules, which as the building block further packs into the target nanostructures depending on π–π interaction with the help of hydrogen bonding/Zn–N coordination bonding interaction between the dimeric supramolecular building blocks for 1 and 2. In particular, the morphological evolution of the nanostructures from helical ribbons to nanotubes has been clearly revealed during the self-assembly process of unsymmetrical phthalocyanine compound 1. In addition, the nanostructures self-assembled from both 1 and 2 were revealed to show good semiconducting properties with the conductivity in the range of 2.04 × 10−5 to 1.28 × 10−4 S m−1 in air due to the ordered one-dimensional π–π stacking enhanced by hydrogen bonding/metal–ligand coordination bonding interaction, which increases to 2.41 × 10−2–2.74 × 10−2 S m−1 after chemical doping with iodine.

High efficiency Nd:YAG ceramic eye-safe laser operating at 1442.8 nm

We report on a diode-pumped Nd:YAG ceramic laser operating at 1442.8 nm for the first time. In our experiment, two different Nd:YAG ceramics with the Nd-doped concentrations of 1.0 and 0.6 at. % and a Nd:YAG with the Nd-doped concentration of 1.0 at. % were used as the laser gain mediums, respectively. At a pump power of 20.7 W, a maximum output power of up to 3.96 W with optical-to-optical efficiency of up to 19.1% was obtained by using the 1.0 at. % Nd-doped ceramic as the laser gain medium. To the best of our knowledge, this is the highest output power of a LD-pumped 1.44 μm Nd:YAG ceramic laser and the highest optical-to-optical efficiency of a LD-pumped 1.44 μm Nd-doped crystal laser.

Organic nanostructures with controllable morphology fabricated from mixed (phthalocyaninato)(porphyrinato) europium double-decker complexes.

The self-assembly behavior of two sandwich-type mixed (phthalocyaninato)(porphyrinato) europium double-decker complexes, namely Eu(Pc)(TClPP) [Pc = phthalocyaninate; TClPP = meso-tetrakis(4-chlorophenyl)porphyrinate] (1) and optically active (R)- and (S)-EuH[Pc(OBNP)(2)](TClPP)] [Pc(OBNP)(2) = phthalocyaninate with two aromatic chiral binaphthayl units attached at the nonperipheral positions] (2), has been comparatively studied. In addition, a hydrophilic additive with intense adhesive ability, sodium carboxymethylcellulose (CMC), was also introduced onto the sandwich-type self-assembly systems to combine with double-decker molecules to induce additional hydrophilic/hydrophobic interaction. In the absence of the additive CMC, the double-decker molecules of 1 self-assemble into nanobelts in mixed solvent of chloroform and methanol. Introduction of two aromatic chiral binaphthayl units onto the nonperipheral positions of phthalocyanine ligand in the sandwich-type mixed double-decker complex 2 leads to the formation of tubal nanostructures. Observation of significant difference in the circular dichroism (CD) spectra of (R)- and (S)-2 in chloroform from their aggregates dispersed in methanol confirms the effective intermolecular interaction due to the interplay of pi-pi interaction between adjacent double-decker molecules with chiral discrimination among chiral side chains at supramolecular level. With addition of CMC, cooperation of intrinsic intermolecular pi-pi interaction with additionally introduced hydrophilic/hydrophobic interaction between adjacent double-decker molecules induces the formation of nanoscale hollow spheres at 45 degrees C during the self-assembly process of 1 and 2.

LD side-pumped Nd:GGG CW laser operating at 1110 and 1105 nm dual wavelengths and 1110 nm single wavelength

A diode-side-pumped continuous-wave Nd:GGG laser operating at dual-wavelength (1110 and 1105 nm) and single wavelength of 1110 nm is demonstrated for the first time. The maximum output power of the 1110 and 1105 nm dual-wavelength operation is 13.2 W. By adjusting the orientation of an insertion mirror, the relative intensities of the two wavelengths can be changed. Thus single wavelength operation at 1110 nm is obtained, and the output power is 9.6 W.

Optical parameters and upconversion fluorescence in Tm3+/Yb3+ codoped tellurite glass

Tm3+/Yb3+ codoped tellurite glass has been prepared. Density, refractive index, optical absorption, Judd-Ofelt parameters and spontaneous transition probabilities of Tm3+ have been measured and calculated, respectively. Intense blue three-photon upconversion fluorescence and S-band (1470 nm) fluorescence were investigated under the excitation of a 980 nm diode laser at room temperature. Judd-Ofelt parameters, strong blue three-photon upcoversion emission of Tm3+ in glass indicate that Tm3+/Yb3+ codoped tellurite glass is a promising blue color upconversion optical and laser material. In addition, experiment results showed the 980 nm laser was more efficient than 808 nm laser when pumping Tm3+/Yb3+ codoped tellurite glass, Tm3+/Yb3+ codoped tellurite glass also could be a promising material for S-band amplification.

Diode-end-pumped passively Q-switched 1319 nm Nd:YAG ceramic laser with a V3+:YAG saturable absorber

The performance of a LD-end-pumped passively Q-switched Nd:YAG ceramic laser at 1319 nm with a V3+:YAG saturable absorber was demonstrated for the first time to the best of our knowledge. The average output power of 1.8 W was obtained under the pump power of 23.7 W, corresponding to the optical conversion efficiency of 7.8% and slope efficiency of 9%. The minimum pulse width was 128 ns with the pulse repetition rate of 230 kHz, which was attained with a T = 2.8% output coupler at the pump power of 23.7 W.

LD-pumped passively Q-switched Nd:GGG laser at 1062 nm with a GaAs saturable absorber

Abstractwe have experimentally studied the passively Q-switched performance of a diode-pumped Nd:GGG laser at 1062 nm with a GaAs saturable absorber, in the experiment when the pumped power was 9.8 W, the maximum CW output power of 5.1 W was obtained. The optical conversion efficiency and the slop efficiency were 52 and 53%, respectively. The threshold was 0.9 W. In the passively Q-switched regime, we get the average output power of 0.93 W. The shortest pulse width and pulse repetition rate were 7 ns and 188 kHz, respectively.