Direct laser writing (DLW) has the advantages of writing any three-dimensional structure without mask plates, in a simple process flow, and with minimal environmental requirements, and it finds widespread application in micro/nano processing technology. However, owing to throughput limits, single-channel DLW cannot be used for large-area fabrication. Currently, instead of single-channel, multi-channel parallel writing is the most direct and effective approach. The reported methods for generating multiple beams typically rely on the construction of a spatial light path, which has been extensively studied. However, challenges persist in generating large numbers of channels. Issues such as poor spot uniformity, independent modulation problems, and system complexity hinder further application of the DLW technology. To improve the throughput of the DLW technology, we designed and verified a multi-channel parallel lithography technology. This technology can achieve a manufacturing accuracy of 126 nm transversely and 222 nm longitudinally under the condition of a picosecond pulse width, and it can process large-area complex patterns and three-dimensional structures.

In this research, we construct a single-channel fiber DLW system using fiber-optic devices. This method is first validated using the system, after which the number of channels in the system is increased to 10. A femtosecond laser source and a dispersion compensation module for dispersion pre-compensation are employed. The laser beam is split using a spatial light splitter and fiber-optic splitters to produce 10 beams. Each beam is independently modulated using a fiber acoustic-optical modulator (FAOM), and the fiber array outputs 10 Gaussian spots that are closely aligned in the same plane. This system comprises two types of scanning devices: a galvanometer scanner and a three-dimensional translational platform. Using the FAOM and scanning devices, large-size and three-dimensional lithography is realized.

Two photoresists were used to evaluate the optical fiber single-channel system. Initially, the OrmoGreen photoresist produced by Microlight3d was employed to fabricate suspended lines, yielding feature sizes of 126 nm in the transverse direction [Fig. 2(a)] and 222 nm in the longitudinal direction [Fig. 2(b)]. In addition, hemispherical and circular ring structures were printed to confirm the three-dimensional writing capability of the system [Figs. 2(c)?(d)]. Subsequently, AZ5214, a common positive photoresist, was used to assess the performance of the system further. Figures 3(a)?(b) show the writing ability of AZ5214 as a positive photoresist. Upon expanding the system to 10 channels and subsequent calibration, the pulse width of the system was measured. The output power of the fiber acousto-optic modulator was within 6 mW and the beam pulse width ranged from 2 ps to 7 ps. This variance was caused by the difference in the fiber length and coupling efficiency of each optical splitter. The gaps of the 10 channels were determined by the fiber array device and could not be flexibly adjusted; therefore, we calibrated the average channel gap. The average gap of the 10 channels was 12.54 μm, and the standard deviation was 0.01 μm. Finally, we used the 10-channel system to print three structures (Fig. 5) to verify the 10-channel parallel processing capability. Nevertheless, multi-channel optical fiber systems still face many challenges, including achieving uniformity or consistency in writing between channels and addressing femtosecond pulse broadening issues caused by dispersion.

A 10-channel parallel DLW system based on fiber devices is introduced in this paper. By utilizing an FAOM for independent modulation, the system overcomes the limitations observed in most previous multi-channel systems, which are typically restricted to writing repetitive and periodic structures. The system achieved feature sizes of hundreds of nanometers. In addition, the system has many strengths, including compatibility with various photoresists, the ability to produce three-dimensional graphics, and large-area writing. Compared to spatial light multi-channel DLW systems, the system introduced in this study demonstrated compactness and ease of adjustment. This study underscores the significant application potential of fiber-optic devices for realizing high-throughput DLW technology. Through further optimization, it is feasible to expand the number of channels to hundreds, which holds considerable significance for advancing DLW technology.