Research team develops direct laser writing system for high-resolution, high-efficiency nanofabrication

Peripheral photoinhibition (PPI) direct laser writing (DLW) is a lithography technique used to fabricate intricate 3D nanostructures that are widely employed in photonics and electronics. PPI-DLW uses two beams, one to excite the substrate and cause polymerization, and the other to inhibit and quench excitation at the edges. Capacity is limited on some systems, which can be improved through multifocal arrays. However, calculating these beams requires a lot of time and memory.

Recently, a group of researchers from Zhejiang University developed a parallel lithography of peripheral photoinhibition (P³L) system that can achieve higher efficiency nanoscale manufacturing. His work is published in advanced photonics

“The P³The L system uses two channels, which allows the execution of different printing tasks and enables the system to fabricate highly complex structures with different periodicities,” says lead author Xu Liu.

the p³The L system consists of a physical arrangement of eight modules. The system starts with two imprint channels, consisting of a solid excitation dot and a donut-shaped inhibition beam. The two beams are first stabilized and then split into two sub-beams using a polarization filter. This allows for individual on/off control of each sub-beam through an acousto-optic modulator. The two secondary bundles then recombine to recover the excitation and inhibition bundles. The beams are then modulated using spatial light modulators. Finally, the two beams are combined and passed through a microscope, after which they are focused on the substrate as two points.

Individual control of each sub-beam allows the printing of non-periodic and complex patterns simultaneously, without compromising scanning speed, thus doubling the efficiency of the system. Adjusting the position and spacing of the two points is easy. These features make the proposed system more flexible and functional than conventional systems with uniform focus control.

The researchers confirmed the feasibility and potential of the system by fabricating a variety of nanostructures. They first fabricated a sub-40 nm 2D nanowire. A suspended nanowire less than 20 nm thick was also fabricated. After that, the researchers created two rows of alphabetic patterns by printing dots 200 nm apart. Finally, they fabricated 3D structures, including aperiodic cubic frames, hexagonal grids, wireframes, and spherical architectures, all of which demonstrated exceptional resolution.

Identical on/off control of each bulb increases the flexibility of the system and allows rapid fabrication of complex, non-periodic patterns and structures. The system’s parallel scanning function also reduces the cost of time required to manufacture complex patterns and structures on a large scale. Also, the new P³The L system achieves a lithographic efficiency double that of conventional systems, regardless of whether the structure is uniform or complex.

Speaking of the future potential of the work, Xu Liu says, “Multifocus parallel scanning and PPI have the ability to overcome current challenges in DLW optical fabrication and improve the fabrication of blazed gratings, microlens arrays, microfluidic structures, and metasurfaces. The system proposed could further facilitate the realization of high-performance, high-resolution, portable DLW.”

Based on these results, it is clear that the proposed P³The L system will serve as a useful tool for the development of a wide range of fields that use nanotechnology.