Photorefractive effect of smectic liquid crystals and their application to laser ultrasonic remote sensing

The photorefractive effect of flexoelectric smectic liquid crystal mixtures was investigated and applied to a laser ultrasonic measurement. Smectic liquid crystal mixtures, composed of smectic-C liquid crystals, photoconductive chiral compounds, and a sensitizer, are known to exhibit a fast photorefractive effect. The principle of the ultrasonic measurement is that a nanosecond laser pulse is shot on an object to cause an ultrasonic vibration, a continuous laser beam is irradiated on the object, and the ultrasonic variation is detected using photorefractive two-beam coupling. This method can be used to investigate the thickness and the internal structure of an object without contact.