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 (355 nm) 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.
7-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.
