Zugeng Wang

Surface-enhanced Raman spectroscopy investigation on human breast cancer cells.

BackgroundNanoparticles are potentially used for early cancer detection, accurate diagnosis, and cancer treatment.ResultsIn this paper, the breast cancer cells treated with gold colloidal suspension were carefully studied by surface-enhanced Raman scattering (SERS) spectra. Raman spectroscopy combining with high-resolution electron microscope is employed to investigate the interaction of gold nanoparticles (GNPs) with the intracellular components. The TEM images show that the GNPs are taken into the living cells and enveloped into some vesicles named ‘lick up vesicles’ in the cytosol.ConclusionsThe SERS spectra and SERS mapping of cells indicate that the major Raman bands are mostly assigned to the vibration characteristics of proteins, and the C-H in-plane bending mode of the substituted benzene in Phenylalanine is remarkably enhanced. Finally, the interaction mechanisms of the GNPs with the intracellular components are further discussed in detail.

Complex periodic micro/nanostructures on 6H-SiC crystal induced by the interference of three femtosecond laser beams

We reported three types of complex micro/nanostructures on 6H-SiC crystal induced by the interferences of three femtosecond laser beams by arranging three types of laser polarization combinations. The micro/nanostructures are composed of two parts: two-dimensional long-periodic micropatterns determined by the interferential intensity pattern and short-periodic nanopatterns determined by the interferential polarization pattern. Theoretical calculation indicates that the different polarization combinations will lead to a distinct complex interferential polarization pattern and intensity pattern, and they accord well with the experimental results.

Optical limiting response in a unsymmetrical dithiolene metal complex (Me4N)2[Zn(dmit)(Sph)2]

Abstract We report the measurements of reverse saturable absorption (RSA) and optical limiting responses in a unsymmetric dithiolene metal complex (Me 4 N) 2 [Zn(dmit)(Sph) 2 ] with nanosecond and picosecond laser pulses at 532 nm. The experimental results show that the triplet–triplet absorption is responsible for the measured RSA, resulting in optical limiting responses. The measured data can be well simulated by a rate equation model to obtain the absorption cross-section of the excited state.

Two-photon hybrid resonance laser and photodissociation laser by two-photon pumping covering a wide wavelength region in the potassium vapor

Abstract This paper reports the results about the laser generation based on the two-photon hybrid resonance and on the photodissociation by two-photon pumping covering a wide wavelength region respectively. In the former, 3.66, 3.64, 3.16, 3.14, and 2.71 μm laser lines were obtained by collision energy transfer from a potassium dimer in an excited state to the potassium atom in the ground state, and then followed by the resonance excitation of the potassium atom from the 4P to 6S state. In the latter, 2.71, 3.14, and 3.16 μm dissociation laser lines were obtained by two-photon pumping of the potassium dimer covering a wide pumping range about 650 A at the red wavelength region.

Resonant third-order optical nonlinearity of a new subphthalocyanine

Abstract We have investigated the resonant third-order nonlinear optical properties of a new subphthalocyanine (bromoboron trineopentyloxy-subphthalocyanine) using picosecond degenerate four-wave mixing. The measured χpure(3) was 6.9×10 −10 esu . The second hyperpolarizability 〈γ〉 value is 3.0×10 −31 esu . The response time of χ(3) was determined to be less than the resolution of optical pulse duration (

π-electron density dependence of third-order optical nonlinearities in poly(1,4-phenylene vinylene) derivatives

The third-order nonlinear optical properties of poly(1,4-phenylene vinylene) (PPV), poly(2-bromo-1,4-phenylene vinylene) (BrPPV) and poly(2-chloro-1,4-phenylene vinylene) (ClPPV) were studied by forward degenerate four-wave mixing (DFWM). They have large and ultrafast third-order optical nonlinear responses, which mainly arise from the distortion of the large π-conjugated electronic charge distribution in the backbone. It was found that there was a significant contribution to π-electron density and thus χ(3) values from the substituents at the phenylene ring.

Optical nonlinear properties and optical limiting for [(n-Bu)4N]4[MoS4Cu]4

We report the nonlinear optical properties of one metal cluster [(n-Bu)4N]4[MoS4Cu]4 by picosecond and nanosecond laser pulses. The optical limiting response is measured by a transmission technique and the nonlinear absorption by a Z-scan technique. The experimental data are theoretically fitted, the mechanism for the optical nonlinearities and the optical limiting properties is discussed, and the absorption cross sections of the ground states and the excited states are evaluated by a rate equation model.

Field-free molecular orientation enhanced by two dual-color laser subpulses.

In this paper, we theoretically show that the field-free molecular orientation created by a single dual-color laser pulse can be significantly enhanced by separating it into two time-delayed dual-color subpulses. It is indicated that the maximum enhancement of the molecular orientation created by two time-delayed dual-color subpulses can be achieved with their intensity ratio of about 1:2 and by simultaneously applying the second one at the beginning of the rotational wave packet rephasing or the end of the rotational wave packet dephasing induced by the first one. It is also shown that the enhancement or suppression of the molecular orientation can be coherently manipulated by varying the relative phase between the fundamental field and its second harmonic field of the second dual-color subpulse, and its enhancement is obtained around half rotational period.

The generation of UV and violet diffuse band stimulated radiation in a sodium dimer

Abstract UV (340.0–380.0 nm) and violet (405.0–460.0 nm) diffuse band stimulated radiation was generated via one-photon resonant excitation of the 3p level and two-photon resonant excitation of the 4D level of atomic Na in the vapor. The result was compared with the violet diffuse band of Na 2 obtained by one photon excitation up to the molecular state C 1 π u . The mechanisms involved were discussed.

Selective excitation of femtosecond coherent anti-Stokes Raman scattering in the mixture by phase-modulated pump and probe pulses.

In this paper, we present a feasible method to realize and improve the selective excitation of femtosecond coherent anti-Stokes Raman scattering (CARS) in a mixture. We theoretically show that, by shaping both the pump and probe pulses with the pi phase step, the CARS signal from one quantum system can be enhanced and simultaneously that from the other quantum system is effectively suppressed. Comparing with only shaping the probe pulse [D. Oron, N. Dudovich, D. Yelin, and Y. Silberberg, Phys. Rev. Lett., 88, 063004 (2002)], the selectivity of femtosecond CARS by shaping both pump and probe pulses can be greatly improved. Finally, we experimentally compare two shaping schemes by investigating the selective excitation of the femtosecond CARS in the mixture of dibromomethane (CH(2)Br(2)) and chloroform (CHCl(3)).