Femtosecond Z-scan Technique Research Articles

Femtosecond Nonlinear Optical Properties of Au/SiO2 Composite Thin Films Prepared by a Sputtering Method

The imaginary part of the third-order nonlinear susceptibility, Im\ olimits[χ(3)], of Au/SiO2 films was measured by the femtosecond Z-scan technique near the surface plasmon resonance (SPR) peak. The Im\ olimits[χ(3)] of the film containing Au particles with the mean diameter of 14.0 nm was estimated to be -1.6×10-8 esu. The response time of the film measured from the decay of the differential transmission of the pump–probe experiment was 1.0 ps at the SPR peak.

A systematic femtosecond study on the two-photon absorbing D-π-A molecules–π-bridge nitrogen insertion and strength of the donor and acceptor groups

The two-photon absorption (2PA) properties of a series of dyes containing donor and acceptor groups connected via a π-electronic bridge were studied by using a femtosecond Z-scan technique. It was found that the nature of the π-electronic bridge does not substantially affect the measured 2PA intensities. In the case of the substituted azobenzenes the decrease of the strength of the donor and/or acceptor groups leads to decrease of the 2PA intensity, the effect of the acceptor strength being greater.

Two-Photon Absorption and Excited-State Energy-Transfer Properties of a New Multibranched Molecule

This paper presents a molecular design for a two-photon absorbing structure, which contains a two-dimensional molecular architecture with four arms and one bridging unit, each of these segments having an extended π-conjugation and capable of producing two-photon absorption in different spectral ranges. Two chromophore units of a triphenylamine derivative dye, (N, N-di[4-{4-(5-[4-tert-butylphenyl]-1,3,4-oxadiazol-2-yl)styryl}phenyl]amino)benzene, were linked with a π-conjugated di-2-thienylethenylene bridging unit to form a new multibranched compound, bis(5-[4-{N,N-di(4-[4-{5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl}styryl]phenyl)amino}styryl]thien-2-yl)ethenylene. Linear absorption spectra and luminescence spectra of the component and the multibranched chromophores revealed a hypochromic effect for the multibranched dye. A very effective energy transfer from the excited arm units to the π-conjugated bridging unit is observed. The two-photon cross-sections were measured using the femtosecond Z-scan technique at several excitation wavelengths in the 620−800 nm range. Comparing the nonlinear absorption coefficients observed for the constituent chromophore dyes with that for the multibranched compound, we found that the arm units make the dominant contribution to the two-photon absorption when the wavelength of excitation is longer than 720 nm.

Two-photon absorption study of GaN

Two-photon absorption coefficients of GaN for below band gap ultraviolet wavelength and midgap infrared wavelength were measured by using femtosecond pulsewidth autocorrelation and Z-scan techniques. Large two-photon absorption coefficients were obtained. Taking advantage of the large two-photon absorption, we have demonstrated two-photon confocal imaging of a GaN thin film. Direct correlation was found between the yellow luminescence and suppression of bandedge luminescence.

Large saturation of absorption of CdSSeTe nanocrystallites in glass measured by femtosecond Z-scan technique

The optical non-linearity of CdSSeTe nanocrystallite-doped glasses has been studied using a single-beam, femtosecond Z-scan technique. We have observed very large absorption saturation in a composite of CdSSeTe nanocrystals in a glass host compared with CdS or CdSe, although we have not reached the saturation limit. The wavelength and power dependence of absorption saturation in these composites are reported. The experimental data are interpreted by two-level model system. A comparison is also made with other nanocrystallite composites with different stoichiometric compositions. Copyright © 2000 John Wiley & Sons, Ltd.