Congshan Zhu

Exciton spectra of SnO2 nanocrystals with surficial dipole layer

Abstract Experimental results of absorption, luminescence and excitation spectra in both bare and coated, SnO2 nanocrystals are given. It is found that when the SnO2 nanocrystals are coated by a layer of organic molecule, the absorption edge shifts to the longer wavelength detection as the particle size decreases, which is inconsistent with that of bare SnO2 nanocrystals. It is demonstrated that the size and surface situations of nanocrystals have great influence on their spectroscopic properties. The experimental data are discussed in terms of the quantum confinement effects and dielectric confinement effects.

Electron spin resonance properties of ZnO microcrystallites

The preparation of ZnO microcrystallites using a microemulsion method and their electron spin resonance (ESR) properties are reported for the first time. It was found that the ZnO microcrystallite exhibits an ESR signal at room temperature, in contrast to that of bulk ZnO. The results confirmed that there exist a large amount of oxygen vacancies on ZnO surfaces which provide the observed ESR signals.

Optical nonlinear properties of PbS nanoparticles studied by the Z-scan technique

Abstract The optical nonlinear properties of PbS nanoparticles in polyvinyl alcohol (PVA) sol were studied by the Z-scan technique with 50 ps pulses at 530 and 1060 nm, respectively. The sample under these two excitations shows quite contrasting nonlinear optical responses. The saturation absorption at 520 nm is observed while at 1060 nm the two-photon absorption. The optical limiting of PbS nanoparticles were also investigated at 530 and 1060 nm

Optical nonlinearities of Fe2O3 nanoparticles investigated by Z-scan technique

Abstract The single beam Z-scan technique has been used to measure the third-order nonlinear refractive index, γ, the two-photon absorption coefficient, s, and the variation of refractive index per unit photoexcited carrier density σ r , and the free carrier absorption cross section σ ab for quantum-confined Fe 2 O 3 nanoparticles coated by a layer of organic molecular in toluene and bare particles in hydrosol. For coated Fe 2 O 3 nanoparticles, the ratio γ/s is enhanced by a factor of five compared to the bare sample. Their figures of merit related to linear and two-photon absorption for ultrafast all-optical devices application were determined.

Large nonlinear optical properties of Fe2O3 nanoparticles

Abstract Nonlinear optical properties of Fe 2 O 3 nanoparticles were investigated by the signal-beam Z-scan technique with Ar + and Ne–He lasers. The largest reported effective nonlinear coefficient, n 2 =−8.07×10 −7 cm 2 / W , was obtained. It is demonstrated that the nonlinear optical response originals from quantum confinement effect.

OPTICAL NONLINEARITY OF BI2O3 NANOPARTICLES STUDIED BY Z-SCAN TECHNIQUE

The third-order optical nonlinear susceptibilities of Bi2O3 nanoparticles coated by a layer of stearic acid in toluene sol and bare in hydrosol were measured by the Z-scan technique. The nonlinear susceptibility of the coated Bi2O3 nanoparticles was found to be two orders of magnitude greater than that of the bulk Bi2O3. For the coated Bi2O3 nanoparticles, the figures of merit related to linear loss and two-photon absorption were determined.

Optical limiting properties of In2O3 nanoparticles under cw laser illumination

Abstract We have measured the effective intensity dependent nonlinear coefficient n 2 of In 2 O 3 nanoparticles with surface modification by Z-scan technique. The optical limiting properties of coated In 2 O 3 nanoparticles under cw laser illumination were investigated. Novel absorption at different wavelengths as a function of incident intensity was observed.

Nonlinear optical absorption and refraction by CdTe microcrystals doped in glass

The two-photon absorption coefficient β and the bound electronic nonlinear index γ of CdTe microcrystals doped in glass were measured by the Z-scan technique. It was found that the figure of merit γ/β of the CdTe microcrystals with nanometer size is enhanced compared to that of bulk CdTe. The optical Stark effect in the nanometer-sized CdTe is the possible origin of the enhanced nonlinearity.

The infrared vibration characteristics of SnO2 nanoparticles

The infrared vibration characteristics of SnO2 nanoparticles with different sizes were studied using the infrared spectra. The Frohlich modes were observed in experiments and compared with the theoretical values. The influence of phonon localization resulting from quantum size effects on the infrared spectra of SnO2 nanoparticles is discussed.

Effect of solvent vapor on optical properties of Pr4VOPc in polymethylmethacrylate

Dye‐in‐polymer (DIP) films consisting of soluble Pr4VOPc (vanadyl phthalocyanine having four propyl substituents) dye and polymethylmethacrylate (PMMA) were prepared by spin‐coating process. Pr4VOPc precipitates as a glassy phase in pure PMMA matrix during the film formation. Upon exposure of these DIP films to organic solvent vapor, stable crystalline Pr4VOPc, which has stronger absorption in the near‐IR region and larger nonlinear refractive index n2 than the glassy phase, forms. The organic solvent vapor promotes the solubilization and crystallization of the dye, plastication of the polymer chains, and migration of the dye. The nonlinear refractive index n2 and optical spectra of the DIP films were measured, and the change rule has been discussed in terms of electron transition and molecular packing of Pr4VOPc.