High nonlinear optical coefficient ( χ3=10 −7 esu) of cyanine dye J aggregates doped silica film synthesized by a simple sol–gel method

We have synthesized, for the first time, a thin silica film doped with condensed J aggregates of 1,1′-diethyl-2,2′-cyanine bromide dye using a simple sol–gel method. The film is homogeneous in thickness and stable at room temperature. The J band formed in the spin coating process is independent of polarizer angle and the film is isotropic without any dichroism. The high optical nonlinearity ( χ 3=5.0×10 −7 esu) of the film at the resonance wavelength (=577 nm) of the J aggregates was first observed by Z-scan using a 180 fs pulse laser at 77 K under a vacuum (