Qi Fang

Synthesis, structure and properties of a new nonlinear optical material: zinc cadmium tetrathiocyanate

In this communication, a new nonlinear optical crystal of coordination complex, zinc cadmium tetrathiocyanate (ZnCd(SCN)4), is reported. It was successfully synthesized through several reactions in water. For the crystal structure, optical and thermal characterization were determined by elemental analysis, X-ray diffraction, infrared spectroscopy, differential scanning calorimeter, thermogravimetric analysis, and transmission spectrum. It belongs to the tetragonal system, space group I4, with a = 11.135(2), c = 4.3760(10) A, and z = 2. It exhibits powder SHG efficiencies superior to that of cadmium mercury thiocyanate (CMTC) and over 10 times that of urea, and the UV transparency cutoff is 290 nm, which is shifted to violet band 90 nm, compared with that of CMTC.

Two-photon pumped lasing stilbene-typechromophores containing various terminal donor groups: relationship betweenlasing efficiency and intramolecular charge transfer

A series of new two-photon pumped (TPP) up-conversion nlasing dyes, named as CSPI, DPASPI, PSPI, DEASPI and HEASPI respectively, nhave been synthesized. These dyes are stilbene-type chromophores end-capped nwith the same acceptor group but with varied donor groups, whose different nelectron-donating abilities can be ordered by 1H NMR chemical nshift data. PM3 calculations show that attaching different donors changes nthe bond length alternation (BLA) and charge density distribution of the styrylpyridine nskeleton. These chromophores exhibit different two-photon up-conversion nemission behavior. Pumped by a 1064xa0nm, ∼40xa0ps mode-locked nNdxa0∶xa0YAG laser pulses, all chromophores showed two-photon npumped (TPP) up-conversion laser emission, but the efficiencies showed na difference of about two orders of magnitude, ranging from an up-conversion nefficiency of 10.7% for DEASPI to 0.13% for CSPI under the same experimental nconditions. The results show that the efficiency of two-photon pumped nemission is related to the intramolecular charge transfer character of the nchromophore. The two-photon pumped lasing efficiency increases both with ndecreasing BLA and with increasing intramolecular charge transfer character, nmeasured by the parameter Δρ1,2.

Symmetric and asymmetric charge transfer process of two-photon absorbing chromophores: bis-donor substituted stilbenes, and substituted styrylquinolinium and styrylpyridinium derivatives

Two-photon absorption properties of a series of symmetrically substituted stilbenes and asymmetrically substituted stilbene-type derivatives with the same conjugated length have been investigated. The effective two-photon absorption cross sections, δTPA, as large as 62.0xa0×xa010−48xa0cm4xa0sxa0photon−1 for D-π-D molecules and 48.5xa0×xa010−48xa0cm4xa0sxa0photon−1 for D-π-A counterparts have been observed. The effect of these two types of chromophores on the peak position of the linear absorption, one-photon fluorescence as well as two-photon absorptivity is reported. Dipole moment change between the ground and the first excited states (Δµge), and the transition dipole moment between the first and second excited states (Mee′) nhave also been calculated. It was found that the asymmetrically substituted derivatives possess relatively large Δµge, whereas the symmetrical counterparts show an increase in Mee′. Although a large two-photon absorption resonance is due to the simultaneously high values of Mee′ and Δµge, correlated to intramolecular charge transfer, the former function is larger. These results obtained have demonstrated that the magnitude and the peak position of two-photon absorption depend not only on the amount but also on the direction of the intramolecular charge transfer.

Trivalent boron as acceptor in D–π-A chromophores: synthesis, structure and fluorescence following single- and two-photon excitation

A series of new donor-pi-acceptor type compounds with trivalent boron as acceptor which show strong two-photon excited up-conversion fluorescence have been synthesized and one crystal structure described.

Synthesis, structures and two-photon pumpedup-conversion lasing properties of two new organic salts

We have synthesized two new organic salts, trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium toluene-p-sulfonate (abbreviated as nHMASPS) and trans-4-[p-(N-hydroxyethyl-N-ethylamino)styryl]-N-methylpyridinium ntoluene-p-sulfonate (abbreviated as HEASPS). X-Ray diffraction nanalyses reveal that HMASPS crystal belongs to the P21/n nspace group, with water molecules co-crystallized in the crystal and forming nthe monohydrate with the formula of C17H21N2O+·C7H7O3S−·H2O, while HEASPS belongs to the Pspace ngroup, with no solvent molecules. Pumped by a 1064xa0nm, 50xa0ps nlaser pulse at 2.02xa0mJ input energy, an up-conversion lasing of n0.169xa0mJ output energy can be obtained with 0.05 M HMASPS–DMF nsolution, and the output/input efficiency is 8.4%. A 0.05 M HEASPS–DMF nsolution exhibits a lasing efficiency of 9.1% with input and output energy nof 1.90xa0mJ and 0.173xa0mJ respectively.

Growth of cadmium mercury thiocyanate single crystal for laser diode frequency doubling

Abstract Cadmium mercury thiocyanate (CdHg(SCN) 4 , CMTC) crystal is one of the most efficient nonlinear optical crystals among complex crystals. Two different solvent mixtures of water–NaCl and water–KCl suitable for growing CMTC crystal are reported for the first time. A typical single crystal of CMTC with size 18×18×25xa0mm 3 was grown from a water–NaCl mixture solvent by using temperature-lowering method.

Growth of zinc cadmium thiocyanate single crystal for laser diode frequency-doubling

Abstract Zinc cadmium thiocyanate (ZnCd(SCN) 4 , ZCTC) crystal is a promising nonlinear optical material as the source of blue–violet light by laser diode frequency-doubling. A series of experiments on the growth of ZCTC crystal are reported in this paper. A larger single crystal, with size 7×7×13xa0mm 3 , was successfully obtained from the NH 4 Cl–NH 4 SCN–H 2 O mixed solvent by using the solvent-evaporation method. The problems in the growth of ZCTC single crystal are discussed and the key to growing large and transparent single ZCTC crystals is proposed.

Polynitrile-bridged two-dimensional crystal: Eu(III) complex with strong fluorescence emission and NLO property

The first polynitrile coordinated lanthanide complex ([Eu(cda)3(H2O)3].H2O) infinity (cda = carbamyldicyanomethanide anion) has been synthesized and the two-dimensional structure coordination polymer exhibits strong fluorescence emission and strong powder second harmonic generation efficiency (16.8 times that of urea).

Growth and properties of mixed crystal Nd:YGdVO4

Abstract Different Gd/Y polycrystalline materials were synthesized by a liquid-phase reaction method and several Nd:YGdVO 4 crystals with low Nd ion concentrations were successfully grown by the Czochralski method. A component analysis was made and the absorption, emission spectra had been measured. The influence of different Gd/Y ratios on the laser properties was also investigated for the first time. The laser experiments have proved that Nd:YGdVO 4 crystals are good laser materials.

Two-photon absorption and nonlinear optical properties of a new organic dye PSPI

Abstract Trans -4-[ p -(pyrrolidinyl)styryl]- N -methylpyridinium iodide (abbreviated as PSPI thereafter) is a two-photon absorption (TPA) dye newly synthesized by our research group. It possesses much larger TPA cross-section and much stronger upconversion fluorescence emission than those of common organic dye (such as rhodamine) when excited with near infrared (IR) radiation. TPA spectrum and upconversion efficiency spectrum of HEASPI solution at various wavelengths were measured. There is 34 nm blue shift for the central wavelength of the TPA induced absorption peak compared with two times of the linear absorption peak. The biggest molecular TPA cross-section σ 2 ′ is 2.85×10 −47 cm 4 xa0s/photon at 930 nm. At 1064 nm, σ 2 ′ is 3.12×10 −48 cm 4 xa0s/photon. The highest efficiency is 3.9% at 1010 nm, whereas 2.9% at 1064 nm. Its optical power limiting properties at 930 nm have also been illustrated.