Torsional Actuators Using LiNbO3 Plates with an Inversion Layer

By utilization of a ferroelectric inversion layer formed in a LiNbO3 plate by heat treatment at just below the Curie temperature, a piezoelectric torsional actuator consisting of a single-crystal plate with no bonding layer can be obtained. The optimal cut suitable for generating torsional motion efficiently without causing bending motion is theoretically examined. It is experimentally demonstrated that torsional actuators fabricated using 140°-rotated Y-cut LiNbO3 plates with an inversion layer as thick as half the plate thickness exhibit no hysteresis and little creep. When an actuator with dimensions of 16×7.0×0.1 mm3 is used as a light deflector, a light beam deflection angle as large as 2.08° is obtained at an applied voltage of 220 Vp-p.