Electromechanical vibration study in freely suspended smectic liquid crystal

Electric field induced vibration of a freely suspended film (FSF) of smecti c liquid crystal has been studied as a function of temperature, applied fie ld and film thickness. By the application of a sinusoidal electric field pa rallel to the film, not only a fundamental but also higher harmonics of the vibration has been observed. In particular, even the fifth-harmonics of th e vibration is excited in ferroelectric liquid crystal (FLC). Electric fiel d dependences of the vibration strength for fundamental and second-harmonic components have been found to be proportional to the electric field and to the square of the electric field, respectively. Temperature dependence of each component of the vibration strength has been also measured in FLC. The fundamental component of the vibration increases steeply around the phase transition temperature from the smectic A (SmA) phase to the chiral smectic C (SmC*) phase, while the second-harmonic component has taken the maximum strength just below the phase transition temperature. When the FSF was in t he SmA phase, the optical response was smaller for the thick film compared with that for the thin film. Oppositely, in the SmC* phase, the film vibrat ion was smaller for the thin dim.