Second harmonic generation coherent interferometry disclosing the orientation of the submerged hemicyanine layer in a Langmuir-Blodgett multilayer structure

Second harmonic generation coherent interferometry (SHG-CI) was first applied to the structural study of multilayered LB films. Two kinds of LB multilayers were prepared by installing a hemicyanine monolayer among the layers of stearic acid by way of either Y-type or Z-type deposition process, and those films were investigated by the SHG-CI method in terms of the molecular orientation of the submerged hemicyanine layer. It was shown that the Z-type structure of the hemicyanine layer was readily achieved and remained stable within the LB multilayers. This was the first example to disclose the direction of the molecular axis of a specific layer sandwiched among nonlinearly inactive foreign layers.