Fabrication of diffractive optical elements on fused silica by femtosecond laser direct writing

In recent years, processing with femtosecond lasers for micromachining has emerged as a new technology with significant roles in high-end manufacturing. By loading phase onto the incident femtosecond laser through diffractive optical elements (DOEs), it can form the desired light field distribution through diffraction. In response to various issues and limitations of traditional DOE processing techniques, this paper proposed a new DOE processing method based on femtosecond laser direct writing on fused silica. Utilizing the saturation phenomenon of fused silica during femtosecond laser processing, craters with dimensions of several hundred nanometers can be processed on the surface of fused silica. Through the control of the parameters of femtosecond laser, the processing of craters with high precision and high controllability on fused silica with can be achieved. This phenomenon can be used to realize the processing of DOE phase distribution according to the specific laser wavelength. Compared to traditional methods, this processing method has the advantages of high precision, high efficiency, and high flexibility. The DOEs processed by this method based on fused silica have high diffractive efficiency, can be used in various high-fluence applications and have good diffraction effects.