An electric field sensor comprises an electric field sensor head (3) for varying an intensity of a propagating light beam in response to an electric field intensity of an input signal received by a reception antenna (1). The electric field sensor head (3) comprises an incident optical waveguide (9), two phase-shift optical waveguides (10) having a variable refractive index which varies in response to the electric field intensity, an outgoing optical waveguide (11), at least one modulation electrode (12) formed in the vicinity of at least one of the two phase-shift optical waveguides (19). The electric field sensor further comprises a resonator circuit (23 connected between the modulation electrode (12) and the reception antenna (1). The modulation electrode (12) has a thickness not smaller than 1 .mu.m. The modulation electrode (12) may comprise a plurality of split electrodes split in a light propagating direction and capacitively coupled. The reception antenna (1) is preferably implemented by a low radiation resistance antenna.
