Chen Wen-Ju

Study on dynamic optical nonlinearities of excited state proton transfer in ethanol solution of 7-hydroxyquinoline

Abstract The dynamic process of 7-hydroxyquinoline with excited state proton transfer has been studied by the pump–probe method in which a three-dimensional degenerate four-wave mixing technique is employed for the probe. The molecular hyperpolarizability and lifetime of the excited state involved in the excited state proton transfer process of 7-hydroxyquinoline are obtained in our experiment. The decay time of the cation excited state is 35 ps and the decay time of the anion excited state is 250 ps. The molecular hyperpolarizability of 7-hydroxyquinoline in the enol form ground state, cation excited state and anion excited state are 1.3±0.2×10 −31 , 8.0±1.0×10 −31 and 5.8±0.8×10 −30 esu, respectively.

Study of energy transfer between rare earth ions in CaS host by photoluminescence spectra

When CaS:Sm3+, Eu2+ is excited at 476.5 nm (Ar+), the emission spectra taken at room temperature and at 77 K are different, indicating that there are two competitive energy transfer processes-Sm3+ --> Eu2+ and Eu2+ --> Sm3+ with phonon participation. So, the luminescence intensity of Sm3+ increases first, and then decreases as the concentration of Eu2+ is increasing

Two-Photon Absorption Properties of Mn-Doped ZnS Quantum Dots

We investigate the two-photon absorption and nonlinear refractive index properties of a quantum dot material based on ZnS nanocrystals doped with Mn isoelectronic impurities, using the Z-scan technique with 532 nm picosecond laser pulses. The Mn-doped ZnS quantum dots have an average two-photon absorption cross section as high as 13600 Goeppert–Mayer units, which turn it into a very promising material for fluorescent label and imaging in biological samples. In addition, we also found that the two-photon absorption coefficient initially increases and then decreases with increasing pulse irradiance, which demonstrates the presence of the higher-order nonlinearity under the strong excitation.

Optical Nonlinear Properties of CdSeS/ZnS Core/Shell Quantum Dots

The optical nonlinear properties of CdSeS/ZnS quantum dots (QDs) are investigated by Z-scan technique using fundamental harmonic generation (1064 nm) of mode-locked Nd:YAG laser for the first time. The experimental results show that two photon absorptions (TPA) occur at input intensity up to 12.5 GW/cm2. CdSeS/ZnS QDs have an average TPA cross section of 13710 GM and large nonlinear refractive index on order of 10-7 esu. The large optical nonlinearities perhaps allow the CdSeS/ZnS QDs to be one kind of candidate material for bioimaging and fluorescence label, optical limiting and all-optical switching.

All-optical switchings of 3-hydroxyflavone in different solvents

3-hydroxyflavone (3-HF) is an organic molecule with an excited-stated intramolecular proton transfer (ESIPT) effect. All-optical switchings and beam deflections of 3-HF in three kinds of solvents (cyclohexane, ethanol and dimethyl sulfoxide) have been investigated by using the third-harmonic generation (355nm) of a mode-locked Nd:YAG laser as a pump beam and a continuous-wave (cw) He-Ne laser (632.8 nm) as a probe beam. The nonlinear refractive indices of 3-HF in the three different solvents are determined by using the Z-scan technique under an ultraviolet (UV) pump beam at a wavelength of 355 nm. It has been found that the optical switching and beam deflection effects result from the change in refractive index of 3-HF under the irradiation of the pump beam. On the basis of the analyses of absorption spectra and fluorescence spectra, we conclude that the change in refractive index of 3-HF is due to not the thermal effect but the ESIPT effect of 3-HF under the pump beam. As the ESIPT is exceedingly fast, 3-HF might be an excellent candidate for high-speed optical switching.

Excited state proton transfer effect of 7-hydroxyquinoline in dimethyl sulfoxide solvent*

Abstract7-hydroxyquinoline (7-HQ) is a kind of organic molecule with excited state proton transfer (ESPT) effect, and can be used as the material for all optical switching. This optical switching takes place via the ESPT effect depending on its intermolecular hydrogen bond formed with the solvent, and can have the effect of all optical switching. 7-HQ can not form intermolecular hydrogen bond with dimethyl sulfoxide (DMSO), so 7-HQ in DMSO solution cannot display the ESPT effect. However, after the solution was radiated by an UV laser, we found that 7-HQ could have ESPT effect. This phenomenon is reported and the mechanism is investigated for the first time in this paper.

Detection of higher excited states of p-fluorotoluene with (3 + 1)RMPI spectra

Abstract In this paper the results of detection of higher excited states of p -fluorotoluene in the gas phase are presented. Within a laser scanning range of 547.0–570.0 nm (3+1) RMPI spectra are obtained, and some vibrational structures on the third electronically excited valence state are observed. According to the polarization characteristic of the multiphoton transition the symmetry of the electronic state is determined as A 1 +B 1 +3pB 2 . Correlated to excited states of benzene, the results show that A 1 +B 1 corresponds to 1 E 1u and 3pB 2 to 3p 1 A 2u . It indicates that the double degeneracy of 1 E 1u state does not yet degrade in p -fluorotoluene. Moreover, it occasionally degenerates with 3p 1 A 2u . Furthermore, the electron distribution in the phenyl ring maintains the symmetry of the D 6h point group consistently like in benzene.

Nonlinear Transmission Property of the Excited State Proton Transfer Molecule 7-Hydroxyquinoline

Nonlinear transmission property of 7-hydroxyquinoline with excited state proton transfer effect was investigated at 355 and 532 nm using picosecond laser pulses. The experiment result shows that the transmissivity of 7-hydroxyquinoline is nonlinear at 355 nm but it is linear at 532 nm. The nonlinear transmissivity of 7-hydroxyquinoline originates from the larger nonlinearity of anion and cation formed in excited state proton transfer process. Therefore, 7-hydroxyquinoline might be used as ultrafast optical amplitude limit material.

The linear and nonlinear optical properties of nanometer-sized In2O3 organosol

The linear and nonlinear optical properties of nanometer-sized In2O3 organosol were investigated by using TEM, ESR, UV-visible absorption spectrum, photoluminescence spectra and Z-scan technique. It was found that the prepared In2O3 organosol showed a series of new optical properties, which can be explained by its special structure. These new optical properties made its application in information optics enlarged.

STUDY OF THREE-PHOTON RESONANCE MULTIPHOTON IONIZATION SPECTROSCOPY OF 3p RYDBERG STATES OF m-DIMETHYLBENZENE WITHIN DYE Rh560

In this paper, we studied experimentally the three-photon resonance four-photon ionization spectroscopy of m-dimethylbenzene within dye Rh560. We found several new 3p Rydberg vibronic states and measured their polarization characters. With the help of the measured polarization quantities, we gave the assignment results of these vibronic states: 9b01, A1; 1301, A1; 19a01, A1; 8a01, A1.