Three-dimensional holographic femtosecond laser parallel processing method with the fractional Fourier transform for glass substrates

A novel three-dimensional (3D) holographic femtosecond laser parallel processing method with the fractional Fourier transform was proposed for arbitrary microstructures inside glass materials. In this system, the femtosecond laser is modulated by the spatial light modulator and then passes through the objective lens to achieve 3D microstructures without additional optical or mechanical motion support. Relying on the advantages of the fractional Fourier transform, a new expansion in laser 3D processing was realized. A 3D distributed microstructure array was successfully etched using a single irradiation, and a spatially distributed seven-layer wire microstructure was prepared through a single linear scan, in which the interlayer interference can be avoided by optimizing the fractional order. The analysis of computational and experimental results shows that the fractional holographic processing of 3D complex microstructures is an excellent approach for controlling uniformity, energy output and positional accuracy. The holographic 3D laser parallel processing method with high speed and high resolution has shown considerable potential in precision manufacturing, and it can be believed that it will play a significant role in the advancement of high-end technology in the future.