A study of the mechanical vibrations of a freely suspended (FS) ferroelectric liquid-crystal film has been carried out. Upon excitations by sound irradiation and also by electric-field application, the mechanical vibration of the FS film of the ferroelectric liquid crystal is effectively excited. In the frequency dependence, resonance vibrations are observed for both excitations and the resonance frequencies, and light reflection patterns are found to be different for both excitations, suggesting the different oscillating modes of the FS film for both excitations. In electric-field excitation, the vibration mode, which is consistent with the molecular model of the origin of the vibration due to the reorientation of Ps by Ps⋅E torque is found. In addition, the application of the FS film of the ferroelectric liquid crystal as sensitive acoustic sensors is proposed.

Unique piled circular textures induced by an alternating electric field have been observed in a freely suspended ferroelectric liquid crystal film using a polarizing microscope. Molecular alignments in the textures are clarified and the formation process of the texture is discussed.

Electro-optic measurements on a freely suspended ferroelectric liquid crystal (FSFLC) film with a small spontaneous polarization have been carried out. The optical response depends on the magnitude of the applied electric field. The response to polarization reversal at intermediate field strength shows an anomaly, in which piled 2π-walls are observed. The electro-optic response in the FSFLC film in which the piled 2π-walls appear has been analyzed on the basis of a switching model with a distribution function for the molecular orientation. This theoretical model describes the essential features of our experimental observations of optical transmission during switching.

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