Quan Ren

Crystal growth and physical properties of UV nonlinear optical crystal zinc cadmium thiocyanate, ZnCd(SCN)4

Abstract Zinc cadmium thiocyanate, ZnCd(SCN) 4 (ZCTC) single crystals of optical quality have been grown from aqueous solution by controlled evaporation at 40 °C. The morphology of the crystal was indexed. Raman spectroscopy, refractive indices, optical transmission and optical damage threshold of the ZCTC crystal were all performed at room temperature. Violet and ultraviolet (UV) light output by frequency doubling of a 808 nm GaAlAs laser diode and a continuous wave Ti:sapphire laser at 760 nm were achieved. The dielectric constants, piezoelectric strain constants, electroptic coefficients, and direct current resistivities have also been measured.

Growth and properties of UV nonlinear optical crystal ZnCd(SCN)4

Abstract A second-order nonlinear optical coordination crystal, zinc cadmium thiocyanate, ZnCd(SCN) 4 (ZCTC) was grown as a frequency doubler, emitting UV light. A large typical single crystal with dimensions up to 15 × 7 × 7 mm 3 has been obtained by slow solvent-evaporation method for the first time. The infrared (IR) spectroscopy and X-ray powder diffraction (XRPD) of single crystals were performed at room temperature. The specific heat of the crystal has been measured to be 367.9 J/mol.K at 300 K. The thermal expansion coefficients, c- and a-oriented, have been measured to be −1.69 × 10 −5 and 1.95 × 10 −4 K −1 , respectively. The second harmonic generation (SHG) efficiency of ZCTC crystal is 51.6 times as high as that of urea reference, and the measured transmittance spectra from 190 to 3200 nm showed that the UV transparency cutoff occurs at 290 nm and the transmission is 73.22% at 380 nm. UV laser light of wavelength 380 nm has been achieved by the frequency doubling of a 760 nm laser diode at room temperature.

A new aromatic organometallic nonlinear optical crystal: [Bis-4-nitropyridine-N-oxide cadmium chloride]

Abstract A new nonlinear optical crystal BPONCC [Bis-4-nitropyridine-N- oxide cadmium chloride, Cd(NO2C5H4NO)2Cl2], as a derivative of 4-nitropyridine-N-oxide, is reported for the first time. Preliminary results show that its powder intensity is about 8.2 times higher than that of urea, and the transparency cut-off wavelength is almost same as that of 3-methyl-4-nitropyridine-N-oxide (POM), which is about 420nm. Its melting point is much higher than that of the other 4-nitropyridine-N-oxide derivatives. The crystal structure belongs to space group Fdd2 with cell parameters a = 11.644 A , b = 50.025 A , c = 3.808 A .

Investigation on growth and macro-defects of a UV nonlinear optical crystal: ZnCd(SCN)4

Abstract Large single crystals of the coordination complex nonlinear optical material zinc cadmium thiocyanate, ZnCd(SCN) 4 (abbreviated as ZCTC), were grown from aqueous solutions by the solvent evaporation method. The morphology of the crystals was indexed. The grown crystals were characterized by the powder X-ray diffraction analysis allowing to identify the diffraction planes. Six kinds of macro-defects were found in ZCTC large crystals. These defects include cracks, inclusions, negative crystals, growth striations, sector boundaries and straight pipes. The morphologies and distribution regularities of these defects were observed and analyzed using optical microscopy. Their formation mechanisms and the methods of eliminating these defects are discussed.

Synthesis, crystal structure and saturable absorption in the near-IR regions of a new copper complex of dmit: hexadecyltrimethylammonium bis (2-thioxo-1,3-dithiole-4,5-dithiolato)-copper

A new copper complex of dmit, hexadecyltrimethylammonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)-copper([C16H33(CH3)3N][Cu(dmit)2], abbreviated as CTCU, C16H33(CH3)3N = hexadecyltrimethylammonium, dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate) has been synthesized and its structure determined by X-ray diffraction. The saturable absorption of CTCU at 1053 nm shows promise as a Q-switch dye in the near IR regions.

Growth morphology and thermal properties of the organometallic nonlinear optical crystal: MnHg(SCN)4(C2H6OS)2

Abstract Manganese mercury thiocyanate-bis(dimethyl sulfoxide) MnHg(SCN) 4 (C 2 H 6 OS) 2 (MMTD) single crystals of optical quality have been grown from solution by the slow temperature-lowering method. The X-ray powder diffraction (XRPD) spectroscopy of MMTD crystal was performed at room temperature. The morphology of the crystal was indexed. The thermal decomposition process is characterized by differential scanning calorimetry (DSC). The specific heat of the crystal is 699.5 J mol −1 K −1 at 300 K. The thermal expansion coefficient (TEC) along the a -, b - and c -axis is α 1 =5.33×10 −5 , α 2 =4.51×10 −5 and α 3 =3.10×10 −5 /K, respectively. All the TECs are positive and interpreted on the basis of crystal structure.

Organic Inclusion Complex strategy for designing nonlinear optical crystals for ultraviolet applications

Abstract Based on Molecular Engineering and Crystal Engineering concepts, a new method for designing nonlinear optical (NLO) crystal materials, the Organic Inclusion Complex (OIC) method has been demonstrated. In defining an appropriate optical transparent range with respect to the Molecular Engineering method, small organic molecules containing n-π conjugation were selected as “second order harmonic generation (SHG)-active units”(guests). Together with the Crystal Engineering method, chiral molecules were used as “molecular scaffolding” (hosts) to combine with the “SHG-active units” by hydrogen bonds. The former can provide a nonlinear optical effect. The latter leads to the OIC with a noncentrosymmetric structure and are expected to enhance the macroscopic nonlinearity in a synergistic mode of guest and host by inducing the guest molecular dipole alignment as well as other properties, such as thermal stability, mechanical strength and ease of growth. Here, we report two new inclusion complex crystals, urea-(d)tartaric acid (UDT) and urea-(dl)tartaric acid (UDLT) (here, d means dextral and dl means racemic). UDT and UDLT crystals belong to P2,2,2, and P2, space group, respectively. Bulk size crystals with high optical quality were successfully obtained from aqueous solution by using a temperature-lowering method. The experimental results show that these two crystals demonstrate higher NLO effects and shorter wavelength cutoff.

Refractive index and absorption of lead bromide crystals

Abstract Lead bromide (PbBr2) crystals in [001] orientation were obtained by the Bridgman growth method. The orientation of the principal refractive axes of the crystals was determined, and their principal refractive indices were measured by the least deviation angle at eight selected wavelengths. The optical axial angle and the dispersion of refractive index in the visible spectral range were calculated by Sellmeier’s formula. Optical transmission and reflection spectra were measured and the absorption coefficient α was determined. Using the calculated α(hν) dependence, the bandgap width corresponding to indirect transition was determined.

Preparation and transmission loss of the nano-crystal and polymer composite film BTO/PMMA

Abstract Bismuth titanate, Bi 4 Ti 3 O 12 (BTO), is a typical ferroelectric material with useful properties for optical memory, piezoelectric and electro-optic devices. Its nano-crystals were compounded by the chemical solution decomposition technique. The structure and size of BTO were analyzed by X-ray diffraction and transmissive electron microscopy. Two sorts of composite films BTO/polymethylmethacrylate with different weight ratio of BTO were prepared by spin-coating method at certain conditions. In this article, the scattering loss in thin films was obtained using an imaging technique.

Optical constants of the nano-crystal and polymer composite thin film PbTiO3/PEK-c

Composite thin films of PbTiO3 nano-crystals and high transparency PEK-c polymer were prepared by spin coating. The size of PbTiO3 nanocrystals was evaluated to be 30–40 nm. The transparency spectra of PEK-c composite thin film in 360–800 nm were measured. The optical constants n, k of the film in the wavelength range 400–620 nm were investigated by the transmission spectrum. The dispersion of refractive index fits well to a three-term Sellmeier relation. At 633 nm wavelength the refractive index of PbTiO3/PEK-c film was measured to be 1.6628 by a prism coupling method and showed a good agreement with the calculated value using the Sellmeier relation.