The invention relates to an optical device (100) comprising: a waveguide (200) comprising a core (210) extending along an axis of symmetry XX′, and encapsulated in a cladding layer (220), an actuator (400) with width La, overlapping the core (210) and extending along an axis of symmetry YY′ parallel to the axis of symmetry XX′, said actuator (400) is designed so that when a voltage is applied to it, it imposes a mechanical stress at the core (210) to modify its refraction index the device being characterised in that the second axis of symmetry YY′ is offset by a lateral offset D from a plane of symmetry of the waveguide (200) including the first axis of symmetry and perpendicular to the cladding layer (220), the lateral offset is between 15% and 50% of the width La.