Wire cutting is a relatively new technology, the use of ultra short pulse (USP) laser cutting glass substrate of all kinds, including for intelligent mobile phone display soft borosilicate toughened glass, etc.. Wire cutting has the advantage of being able to bend and shape incision, cutting speed up to 2000 mm / sec, and stress free edge quality excellent, without treatment etc.
The self focusing of the peak value beam produced by focused USP laser and the nonlinear optical Kerr effect further enhance the power density until a low density plasma is generated at a threshold. The plasma reduces the refractive index of the material in the center of the beam path and causes the beam to defocus. If the beam focusing optical device is properly configured, the focusing / defocusing effect can be periodically repeated, and a stable filament can be formed. The filament can extend over a few millimeter depth through the optical transparent material. Continuous cutting can be achieved through the relative movement of the workpiece relative to the laser beam to make the filaments produced by these lasers close to each other. The typical filaments are in a range of 0.5 to 1 microns to achieve very high precision cutting.
All the commercial versions of this cutting technology, such as the SmartCleave of the coherent rove company, have used a picosecond laser. These systems are widely used by several display manufacturers at present, because the system can effectively cut glass with a thickness of 10 millimeters.
One drawback in some applications, however, is that these picosecond laser systems are not material neutral. An additional laser process is usually needed to cut the non glassy layer with high quality edges on the mixed layer substrate, such as polyimide and metal on the cut glass.
The peak power of femtosecond laser is much higher than the picosecond laser with average power ratio, and can cut through the traditional (i.e., through the material cutting process of evaporation) almost any material. However, compared with picosecond lasers, femtosecond laser power due to its higher cost and lower but not for wire cutting applications.
However, the industry's demand for multi-layer substrate cutting has prompted laser manufacturers to develop femtosecond lasers that can provide higher average power and more cost effective. Therefore, the researchers used ytterbium fiber instead of the traditional titanium: sapphire as a gain medium to achieve the above purpose.