The present invention relates to a cutting device comprising: a laser source (1) for emitting an initial laser beam (11) in the form of pulses, a shaping system (2) positioned downstream of the femtosecond laser (1), for transforming the initial laser beam (11) into a single phase-modulated laser beam, an optical coupler (3) between the laser source (1) and the shaping system (2), the optical coupler (3) including an optical fibre (31), remarkable in that the cutting device further comprises a polarisation corrector (7) for modifying the polarisation of the initial laser beam (11) at an input end of the optical coupler (3) such that the polarisation of the laser beam at an output end of the optical coupler (3) corresponds to a desired reference polarisation.