An active electro optic modulator

An active graphene electro-optic modulator (7) according to the invention provides active mode-locking in a laser, which modulator comprises two electrodes (8A, 9A), which are connectable to an electric signal generator (10). The modulator (7) comprises a graphene layer (11) and an insulating layer (12), in which layers an electric signal generated by the electric signal generator (10) is arranged to provide an electric field. The light beam of the laser is arranged go through at least the graphene layer (11) and the insulation layer (12,), the insulating layer having a thickness, which is arranged to provide a designed modulation depth.