Hongan Ye

Optical nonlinearity and optical limiting properties of new metal cluster [WOS3Cu3I(2-MePy)3]

Abstract Optical limiting property of the new cluster [WOS 3 Cu 3 I(2-MePy) 3 ] is studied. The comparison of the optical limiting performance of this compound with that of C 60 fullerene has demonstrated to be superior to the C 60 fullerene. The optical limiting behavior of the cluster can be attributed to the excited-state absorption, which is measured by using Z -scan technique.

The fifth-order nonlinearity of CS2

Nonlinear refraction and absorption in carbon disulfide (CS2) has been investigated using the Z-scan technique with a femtosecond pulse laser at a wavelength of 800 nm in a broad intensity range. It is found that the origin of nonlinearity depends on the laser intensity. At low intensity, the nonlinearity is mainly due to the third-order process. The third- and fifth-order processes are at present simultaneously at high intensity. We also find the critical intensity value which determines whether the fifth-order nonlinear process exists or not by analysis of the divided Z-scan curves at different intensities. The nonlinear absorption is attributed to the three-photon absorption and the nonlinear absorption coefficient is 1.37 × 10−27 m3 W−2.

Large picosecond optical limiting properties of a novel planar cluster [WS4Cu4I2(py)6] for picosecond laser pulse

Abstract Large optical limiting response of a novel pentanuclear planar metal cluster [WS 4 Cu 4 I 2 (py) 6 ] were studied by using a double-frequency ns/ps Nd:YAG pulse laser system at wavelength of 532 nm and pulse width of 40 ps. The optical limiting results were discussed based on non-linear absorption theory. The non-linear absorption performance of the metal cluster is better than that of fullerene-C 60 .

Temperature and composition dependent excitonic luminescence and exciton-phonon coupling in CdSeS nanocrystals

The yellow- and red-emitting CdSeS nanocrystals (NCs) synthesized through one-step organometallic synthesis method are uniformly assembled in polymethyl methacrylate (PMMA). A higher-energy emission band originates from band-edge excitonic state appeared at low temperature. With the Se dopant concentration increasing, the luminescent spectra of CdSeS NCs have a red-shifted emission peak and a shorter luminescent lifetime, which is attributed to the existence of trapping state caused by surface defect and Se dopant. CdSeS NC shows a shorter luminescence lifetime and higher energy emission peak in PMMA matrix than that in toluene, indicating that the former is more favorable to transfer energy through exciton-phonon coupling. The upconversion luminescence (UCL) is observed using 800 nm femtosecond laser excitation. The pump power dependence demonstrated UCL spectra of yellow-emitting CdSeS NCs has a slope of 2.2, while that of red-emitting CdSeS NCs has a slope of 1.4. The results demonstrate that the two-photon absorption plays a dominating role when Se concentration of CdSeS NCs is lower, while phonon-assisted UCL by one-photon excitation gradually takes place with the amount of Se dopants increasing.

Optical limiting of metallic naphthalocyanine compound

The optical limiting properties of the metallic naphthalocyanine with high transmission at visible range were studied by using a double-frequency ns/ps Nd:YAG laser system at 532 nm with pulse width of 8 ns. Influences of Br substitute on excited state absorption are significant. The effective excited state absorption model was used to describe the optical limiting effect.

Excited state nonlinearity and optical limiting response of cubane-like shaped metal clusters WSe4(MPPh3)3Cl (M=Ag, Cu)

Abstract The excited state nonlinearity and optical limiting behaviors of cubane-like shaped clusters [WSe 4 (MPPh 3 ) 3 Cl (M=Ag, Cu)] in DMF solution were studied by using a picosecond laser pulses. The excited state absorption capability of clusters [WSe 4 (AgPPh 3 ) 3 Cl] is obviously stronger than that of clusters [WSe 4 (CuPPh 3 ) 3 Cl]. Influences of skeletal atoms on excited state absorption are significant. The fluence-dependent model was used to describe the optical limiting phenomena, and the ratio of absorption cross-section of the excited state to that of the ground state of clusters [WSe 4 (AgPPh 3 ) 3 Cl] is two times greater than that of fullerene.

Design of transverse magnetic-reflected polarizing film

We propose a wideband transverse magnetic-reflected polarizing film composed of Cr and SiO2. Based on the polarization characteristics of reflected light from Cr/SiO2 film, the film can serves as a polarizer to severely attenuate the transverse electric (TE)-polarized light and reflect the transverse magnetic (TM)-polarized light in a wavelength range from 600 to 900 nm. By suitably choosing the film thicknesses, the operation angles of such polarizers can be adjusted over a wide angle range greater than the critical angle of total reflection. Cr/SiO2 film has potential use in surface plasmon resonance (SPR) sensors based on Kretchmann configuration to form integrated structures.

Design and Simulation on Surface Plasmon Resonance Sensor Based on Dual-Wavelength Intensity Modulation

In this chapter, we present a Kretschmann prism coupling surface plasmon resonance (SPR) sensor based on the dual-wavelength intensity modulation. In order to research the sensing properties of the sensor, we select two wavelengths from an amplified spontaneous emission (ASE) light source around 1,550 nm by using optical fiber filters. Different incident angles have been used to simulate the reflectance difference of fitted curves for different refractive indices of gases by using the MATLAB modeling program. The SPR sensor based on the dual-wavelength intensity modulation is a new sensor, which can effectively enlarge the measuring range by changing the incident angle, and can detect more samples. This type of SPR sensor will have various applications in the future.

Sensor based on angular interrogation of Surface Plasmon Resonance by using an elliptical reflector structure

We report a method to make simplification and improve stability of Surface Plasmon Resonance (SPR) sensor by using an elliptical reflector in angular interrogation. The sensitive plate is K7 glass coated with about 50nm gold film. The centers of sensitive plate and the detector are set on each of the two focus of the elliptical reflector respectively. According to the geometrical optics, the detector on one focus can receive the light reflected by the elliptical reflector from another focus when incident angle of input light changes continuously. In addition, we use an opto-coupler switch to adjust the starting point of the rotary stage. The angular interrogation method has been used to study the performance of the sensor in terms of intrinsic sensitivity that includes the width and shifts of the SPR curve for a given refractive index of sensing layer. SPR curves can be observed through the rotation of angular movement of stepper motor, then the resonance angle of gold film is calculated. The preliminary experimental results confirmed that structure can be used as a steady sensor that could detect refractive index changes by precise measurement of the resonance angle and develop this sensor as a practicable high-stability biosensing device.

Optical limiting of platinum nanoparticle stabilized by C 60 derivative

The optical limiting performance of platinum nanoparticle protected by C60 derivative was investigated by using 8-ns laser pulses at a wavelength of 532nm. The investigation indicated the sample could provide enhanced optical limiting even better than benchmark optical limiting material, fullerene C60 dissolved in toluene. The origins of the strong optical limiting were discussed based on reverse saturable absorption and nonlinear scattering.