High-Quality Micropattern Printing by Complex-Amplitude Modulation Holographic Femtosecond Laser

Holographic femtosecond laser printing technology is widely used in the fabrication of micropatterns because of its high efficiency and flexibility. However, speckle noise and energy fluctuations limit the quality of the printed structure. In this study, an improved complex-amplitude modulation holographic femtosecond laser printing method for high-quality micropattern fabrication is proposed. The holographic light field is divided into a signal area and a surrounding noise area. To improve laser uniformity, phase modulation is applied in the signal region to eliminate the speckle noise caused by unconstrained phase interference, and weighted amplitude modulation is introduced in the signal area to improve the calculation accuracy. To precisely control laser energy density, weighted energy efficiency modulation is introduced in the noise region to disperse the energy that exceeds the material damage threshold. Under the synergistic control of laser uniformity and energy density, high-quality micro-pattern structures are printed efficiently. A high-quality millimeter-sized multifocal zone plate with micron accuracy is fabricated with the splicing printing method, demonstrating the potential of micropattern processing and the fabrication of functional devices such as binary optics.