Deflection of a laser beam in response to an electric field was detected with a Sagnac interferometer. A laser beam was aligned to travel between two electrodes immersed in aqueous electrolyte solution. When the alternating electric field was applied perpendicular to the beam axis, the direction of the beam deflection was switched synchronously with the field alternation as expected for the Pockels effect. Broken inversion symmetry is prerequisite to the linear electrooptic effect, but surprisingly the effect was observed even when the laser beam travels through the bulk water a few millimeters away from the electrode surface. [ABSTRACT FROM AUTHOR]