Y. H. Zou

Large third-order nonlinear optical properties of C70 fullerene in the infrared regime

The nonlinear third-order optical susceptibility of C70 in a toluene solution is measured for the first time by the method of degenerate four-wave mixing using 10 ns laser pulses at 1.06 μm. The third-order susceptibility Xin(3)is 5.6×10−12 esu for a C70 toluene solution at a concentration of 0.476 g/l. The correspondent magnitude of the hyperpolarizability γ1111 of the C70 molecule is 1.2×10−30 esu which is in a good agreement with the prediction given by the model of a free electron in a spherical box.

Third-order optical nonlinearities of new two-dimensional pi -conjugated metal-coordinated complexes

We measured third-order nonlinear optical susceptibility for solutions of asymmetric tripyrrane-containing 22 pi -electron aromatic macrocyclic cadmium (Cd2+) and gadolinium (Gd3+) complexes in methanol at 1064 nm using degenerate four-wave mixing and obtained the off-resonant third-order hyperpolarizabilities as 1.2*10-31 and 1.0*10-31 esu, respectively.

Optical limiting properties of buckminsterfullerene C60/C70

Optical limiting behavior through reverse saturable absorption for the solution of a buckminsterfullerene C60/C70 mixture (85% C60 and 15% C70) in toluene has been observed with 10 ns, 530 nm laser pulses. The solution concentration dependence of optical limiting degree is investigated by using the solutions of various transmissivities. The strong influence of the triplet state quenched in the existence of 3O2 is also investigated by comparing the optical limiting process for the argon-degased solution and the not argon-degased solution. The results indicate that buckminsterfullerence is a kind of promising material for light protector.

Femtosecond studies of coherent acoustic phonons in gold nanoparticles embedded in TiO2 thin films

0.15 THz coherent acoustic phonons have been observed in gold nanoparticles embedded in TiO2 thin films by virtue of femtosecond time-resolved transmissivity measurements at room temperature. The generation of these phonons is attributed to the resonant excitation of localized surface plasmon in gold nanoparticles. Their damping time is 55 ps which is acquired by fitting the oscillatory part of time-resolved transmissivity to single exponentially damped cosine function.

Transient optical properties of novel PbS nanoparticles coated with 2,6-O-diallyl-β-CD

The transient optical properties of novel PbS nanoparticles coated with 2,6-O-diallyl-beta-cyclodextrines (CDs) were studied by the femtosecond pump-probe technique. The results show that the ultrafast transient-induced absorption for the novel case. Compared to the PbS nanoparticles stabilized with polyvinyl alcohol (PVA), we find that the process for the novel case is different from the PbS(PVA). We suggest that the CDs surface modification can trap holes on the surface of PbS nanoparticles. This can induce an efficient charge separation between the PbS nanoparticles and its surface and result in an ultrafast-induced absorption for novel PbS nanoparticles

The effect of surface modification on femtosecond optical Kerr effect of PBS nanoparticles

Abstract PbS nanoparticles modified by a polymer (P–PbS) was prepared, and the transient nonlinear optical properties studied by femtosecond optical Kerr effect (OKE) spectroscopy for the first time. A very large nonlinear optical effect (χ(3)∼5.6×10−12 esu) with response time comparable to the laser pulse (∼165 fs) was observed. Comparing with PbS nanoparticles stabilized with PVA and coated with sodium dodecyle benzene sulphonate (DBS), the optical nonlinearity of the PbS nanoparticles modified by the polymer is much larger than those of them. Thereafter, the corresponding nonlinearity mechanism was interpreted.

Study of optical transient relaxation of an Ag-O-Ba thin film

Abstract Under the action of laser pulses with a wavelength of 647 nm and a pulse duration of 150 fs, the optical transient response of an Ag−O−Ba thin film was obtained by the pump-probe method. Optical relaxation is a process in which non-equilibrium electrons, excited by laser pulses and originating from metallic ultrafine particles, return to the equilibrium state. The optical transient relaxation of an Ag−O−Ba thin film consists of fast and slow parts. The fast part occurs in 200 fs and is caused by non-equilibrium electrons entering the matrix. The slow part occurs in 1.6 ps and is caused by non-equilibrium electrons scattering within the lattice and interface between the Ag ultrafine particles and the matrix.

Two-photon resonance enhanced nonlinear optical response in C60-copolymer charge transfer complex

Abstract Ultrafast third-order nonlinearity of C60-poly tetrahydrofurfuryl methacrylate charge transfer complex was measured using femtosecond optical Kerr gate at both 640 nm and 820 nm wavelength. In the materials two-photon absorption region, extra large third-order nonlinear optical response was observed.

Photoexcited carrier diffusion dependence of differential reflection dynamics in InAsxP1−xInP (x ≤ 0.35) strained-multiple-quantum wells

Abstract Using the pump-probe technique, we have observed time-resolved differential reflection in InAs x P 1−x InP (x ≤ 0.35) strained-multiple-quantum wells (SMQWs) and also examined the photoluminescence spectra for the samples studied. The experimental results show that barrier height, interface roughness and quantum-well width influence strongly the differential reflection dynamics. From the experimental results, we have demonstrated that photoexcited carrier diffusion in cap layer and barriers along the direction perpendicular to the sample surface plays a dominant role in determining the differential reflection dynamics.

Femtosecond Optical Kerr Effect of Surface Modified PbS Nanocrystals

Surface modified PbS nanocrystals were fabricated by a novel method and their ultrafast optical nonlinearity was studied by the femtosecond time-resolved optical Kerr effect. A large nonlinear effect (χ(3) similar 5 × 10-12 esu) with a laser pulse limited response was observed. This may be attributed to the reduction of surface trapped electrons due to the surface modification.