Laser Processing by Using Multi Level Free Form 3D Micro-fabricated DOE

A diffractive optical element (DOE) is a promising means of converting a single spot to multiple spots. The multi-level structures of the DOE exhibit a high performance. The DOE structure has the same shape as the multi-level free-form design. This DOE, made of SiO 2 , withstands a high power and peak laser and has a high transmittance in the visible and near-infrared region. Four split beams generated by the DOE are focused by a lens. The split spot size is similar to the spot size without DOE. The fluctuation of intensity of the four spots is obtained as 7.5%. The distance between spots is similar to the design distance. Twenty-one spot simultaneous processing by a pico-second laser by using this DOE on a copper plate was demonstrated successfully for the first time. The processed pattern along the optical axis is in good agreement with the optical simulation.