Method and appliance for cutting materials by multi-beam femtosecond laser

A method for laser cutting dielectric or semiconductor materials, wherein said method comprises the following steps:

• emitting in single-pulse mode at a rate, a laser beam (100) at a wavelength comprised in a spectral band of transparency of the material comprised between 250 nm and 2.2 μm, the laser beam (100) comprising successive bursts of N laser pulses, where N is a natural integer higher than or equal to 2 and lower than or equal to 20, said laser pulses having a duration comprised between 10 and 900 femtoseconds, the N laser pulses of one burst being temporally separated from each other by a time interval defined by a pulse rate of 1 GHz to 10 Ghz and a repetition rate of the successive bursts of N laser pulses being comprised between 1 kHz and 10 MHz;
• spatially splitting the laser beam (100) into a first split beam (101) having a first energy distributed along a first optical axis and, respectively, a second split beam (102) having a second energy distributed along a second optical axis distinct from the first optical axis, the first energy and the second energy are lower than 1 mJ and higher than 1 nJ, the first energy and the second energy being higher than a material modification threshold, and wherein an upper limit of the energy domain is fixed by the threshold of damages which are optically viewable, to the naked eye or using an optical microscope;
• spatially concentrating the energy of the first split beam (101) in a first area (31) of the material and, simultaneously, that of the second split beam (102) in a second area (32) of the material, the first area (31) and the second area (32) being separated from each other and spaced apart by a distance dx, so as to produce localized modifications in the first area (31) and in the second area (32) without generating material ablation or microbubbles in the material;
• and
• adjusting the distance (dx) between the first area (31) and the second area (32), the distance (dx) being comprised between 1 micrometre and about ten micrometres so as to initiate an oriented rectilinear micro-fracture (45), this micro-fracture (45) being oriented along a predetermined direction extending between the first area (31) and the second area (32).