We have discovered large linear electro-optics (Pockels) effect in ZnO crystalline films doped with fluorine and deposited on bare glass. A complex approach including self-consistent band structure calculations together with a Car-Parinello molecular dynamics simulation of the film–glass interface structure was used. The non-centrosymmetric charge density distribution between the ZnO–F wurtzite-like crystalline films and the bare glass substrate causes the observed Pockels effect.