Origin of light-deflection in lithium niobate and lithium tantalate under electric field

Abstract

The deflection of light reported by Müller et al. in lithium niobate [Appl. Phys. B 78, 367-370] and lithium tantalate [Appl. Optics 43 (34), 6344-6347] under electric field originates from refraction at domain-walls, like in ferroelastics. In ferroelectrics the optical discontinuity takes place at domain-walls as a consequence of the electro-optic effect. The theoretical deflection angle calculated from Snell's law is proportional to the square root of the electric field and matches the experimental results reported by Müller et al. for lithium niobate. The finite domain-wall thickness mentioned by the authors is not involved in the deflection phenomenon.

Low drive voltage electro-optic Bragg deflector using a periodically poled lithium niobate planar waveguide

“…Previous publications dealing with EO functionalities in PPLN have already depicted similar effects on both polarizations which is attributed to the presence of a permanent refractive index due to an internal field Ei created by the poling process [4][5][6]. These works reported Ei on the order of 10 6 V/m [18,19]. The shift of  = −7.5 observed for the o-polarization could correspond to a field Ei = 3.5 10 6 V/m.…”