Research on cross-scale stitching processing using femtosecond laser direct writing integrated with in situ detection

Femtosecond laser direct writing (FLDW) serves as a prominent method in the area of micro-nano fabrication. Employing a high numerical aperture objective lens and coordinating galvanometer scanners with translation stages, enables the stitching of samples with cross-scale and large-area features. Errors in the galvanometer scanning optical system and translation stage can significantly impair the quality of the desired micro-structures during cross-scale stitching processing. It is crucial to assess and modify these errors in the FLDW system. Traditional methods require various instruments to measure different types of errors, with each using different references, making them unsuitable for high-precision stitching processing. In this study, we identify errors associated with the galvanometer optical system and the translation stage, which impact the stitching quality of FLDW systems. We propose utilizing critical sites identified by the FLDW technique and acquiring microscopic images of the designated areas using commercial devices. By combining algorithms for extracting image feature points, it not only mitigates the uncertainties linked to manual selection in conventional measurements but also facilitates the precise acquisition of various error values under a consistent reference. Utilizing this technology to calibrate the FLDW system enables the attainment of defect-free femtosecond laser stitching processing. Meanwhile, it inspires the integration of the FLDW system with real-time microscopic stitching measurements on a same platform, which enhances operational convenience and improves manufacturing efficiency for femtosecond laser fabrication. The developed system and method enabled the processing of grid structures and computer-generated holograms characterized by cross-scale and large-area features. Experimental results demonstrate the significant potential for manufacturing large-area micro-nano optical devices.