Tingchao He

Photoinduced anisotropy and polarization holography in a stilbene-containing fluorinated polyimide

A stilbene-containing fluorinated polyimide with high optical and thermal stability was prepared. The photoinduced anisotropy in this polyimide was investigated by measuring its dichroism and photoinduced birefringence. A large photoinduced birefringence (Deltan approximately 10(-2)) was achieved in the polymer. Stable and pure polarization phase gratings without surface-relief structure were written in the polymer film by using two orthogonally linearly or circularly polarized 532 nm beams. The polarization gratings were studied with a 650 nm probe beam by measuring the diffraction efficiency of the probe beam and surveying the conversion of the polarization state of the probe beam.

Study on the nonlinear optical properties of three azo dyes by Z-scan measurements

The nonlinear optical properties of p-aminoazobenzene (PAAB), methyl orange (MO) and p-dimethylamino benzene arsenic acid (PDBAA) were investigated by a single beam Z-scan technique, respectively. Their solution samples all exhibited large nonlinear refractive indices under the excitation of a 633 nm laser. Among the three azo dyes, PDBAA showed the largest value of nonlinear refractive index. Moreover, the process of nonlinear refraction induced by the laser thermal effect was also analyzed in this paper.

Nonlinear-optical and fluorescent properties of Ag aqueous colloid prepared by silver nitrate reduction

The nonlinear-optical properties of metal Ag colloidal solutions, which were prepared by the reduction of silver nitrate, were investigated using Z-scan method. Under picosecond 532nm excitation, the Ag colloidal solution exhibited negative nonlinear refractive index (n2 = -5.17 × 10-4 cm2/W) and reverse saturable absorption coefficient (β = 4.32 cm/GW). The data fitting result of optical limiting (OL) response of metal Ag colloidal solution indicated that the nonlinear absorption was attributed to two-photon absorption effect at 532 nm. Moreover, the fluorescence emission spectra of Ag colloidal solution were recorded under excitations at both 280nm and 350 nm. Two fluorescence peaks, 336nm and 543nm for 280nm excitation, while 544nm and 694nm for 350nm excitation, were observed.

The PDMS-based microfluidic channel fabricated by synchrotron radiation stimulated etching

Micro pattern on PDMS surface has been achieved by using synchrotron radiation (SR) stimulated etching. The experimental results indicated that SR stimulated etching has many advantages, such as extremely high etching rate (as large as 40-50 mum per 10 min), area-selectivity and anisotropy at room temperature, high spatial resolution. Combining the SR stimulated etching with photolithography, a PDMS-based microfluidic channel was obtained. The aim of this work is to develop a three-dimensional microfluidic channel with a special through hole, which is beneficial for cell differentiation, functionality and longevity and cannot be fabricated by conventional direct tooling techniques.

Synchrotron-radiation-stimulated etching of polydimethylsiloxane using XeF2 as a reaction gas

Synchrotron-radiation-stimulated etching of silicon elastomer polydimethylsiloxane using XeF2 as an etching gas is demonstrated.

Photoelectric Properties of Novel Conjugated Copolymers Based on 3, 4-Ethylenedioxythiophene and π-deficient aromatic rings

Four novel donor-accepter (D-A) conjugated polymers based on 3, 4- ethylenedioxythiophene and electron-deficient heterocycle rings were prepared, they have strong tendency to form self-assembled structure in the solid state, which is revealed by X- ray diffraction (XRD) patterns of them in powder. The UV-vis absorption spectroscopy, fluorescence emission spectroscopy and cyclic voltammertry studies suggest that the copolymers are expected to provide enhanced charge-transporting properties for the development of efficient electroluminescent materials. Furthermore, the third-order NLO measurements made with the single-beam Z-scan technique indicate that the copolymers have good third-order NLO response and are desired materials for fabricating nonlinear photonic devices.

A STUDY ON THE SECOND-ORDER NONLINEAR OPTICAL PROPERTIES OF AZO-DYE CHROMOPHORES CONTAINING THE ELECTRON-ACCEPTOR GROUP

Two new azo-dye chromophores containing different electron-acceptor groups were synthesized and characterized by 1H NMR, FT-IR and UV-vis spectra, respectively. The second-order nonlinearity of azo-dyes doped films in poly (methylmethacrylate) and the first hyperpolarizability of the azo molecules were investigated by the Maker Fringe method and the solvatochromic method, respectively. Experimental results showed that both of the two dyes exhibited large second-order nonlinearity (d33 > 30 pm/v) and the stronger electron-acceptor groups in dye molecules would induce larger second-order nonlinearity. This was confirmed by the measurement of the first hyperpolarizability.