Light deflectors using a LiNbO3 torsional vibrator with a polarization-inverted layer

A polarization-inverted layer (inversion layer) can be formed in a LiNbO₃ plate by heat treatment near the Curie temperature. Such a plate with a special orientation can generate a torsional displacement by application of a voltage and therefore serves as a light deflector consisting of a single crystal plate with no bonding layer. The optimal cut suitable for generating only torsional motion efficiently without causing bending motion is theoretically examined. The characteristics of the light deflectors are reported. It is experimentally shown that the torsional actuators fabricated using 140° rotated Y-cut LiNbO₃ plates exhibit excellent linearity and no hysteresis. A light scanning range as large as 24° is attained by application of a voltage of ±1.4 kV to a light deflector with dimensions of 17×5×0.1 mm³. When a small-size deflector with dimensions of 7.5×3×0.1 mm³ is driven at the resonant frequency, a larger scanning range of 20° is attained with a low ac voltage of 16 V_p-p