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Ultrafast direct laser writing of 2D materials for multifunctional photonics devices

Two-dimensional (2D) materials usually refer to materials consisting of mono or a few layers of atoms, with thicknesses varying from one atomic layer to more than 10 nm. Various 2D materials have been successfully isolated, including graphene, hexagonal boron nitride (h-BN), transition metal dichalcogenides (TMDCs), black phosphorus (BP), and perovskite. 2D materials exhibit exotic physical and chemical properties such as atomic thickness, strong nonlinear optical properties, magnetic properties, and excellent mechanical strength that are different from their bulk counterparts, opening new opportunities for nanodevices, especially photonics applications.

Micro/nanostructures and functional devices in 2D materials have been proposed and fabricated by various fabrication techniques in order to fulfil the intriguing properties of 2D materials. Ultrafast direct laser writing (DLW) with the advantages of rich light-matter interaction mechanisms and dynamics; unique three-dimensional (3D) processing capability; arbitrary-shape design flexibility; and minimized thermal effect, which enables high fabrication resolution of tens of nanometers, has been widely used in 2D materials patterning, modification, and functionalization, demonstrating versatile capabilities.

This timely review written by the research group from Swinburne University of Technology captures some of the most exciting advancements in the field and provides an in-depth summary and understanding of the latest functional photonic devices enabled by 2D materials and the DLW method. The review has been published in Chinese Optics Letters, Vol 18, Issue 2, 2020 (Tieshan Yang, Han Lin, Baohua Jia. Ultrafast direct laser writing of 2D materials for multifunctional photonics devices [Invited][J]. Chinese Optics Letters, 2020, 18(2): 023601).

First, a briefly overview of the physical property changes of 2D materials upon laser exposure was provided. Laser-matter interactions may involve several processes: single/multiphoton absorption, material ablation under laser exposure, phase change of nanostructures, and chemical/physical properties modifications. These processes lead to different physical and chemical property changes of materials, like tuning the refractive indices (n) and extinction coefficients (k), bandgap engineering, conductivity changes, and surface wetting properties (hydrophilic or hydrophobic), which are the fundamental basis for various functional photonics or optoelectronics device designs. Furthermore, light and 2D materials interactions can enable micro/nano-patterning, laser thinning, and laser doping of various 2D materials, which are critical for high-resolution processing and functionalization of 2D materials down to a monolayer accuracy. Then, the advantages and limitations of 2D materials functional photonic devices were elucidated, including ultrathin flat lenses, graphene metamaterials, perfect absorbers, holographic displays, etc. fabricated by DLW toward practical applications. Moreover, ultrafast DLW has been used to locally change the nonlinear properties of 2D materials, which offers a new flexibility in directly converting the conventional photonic devices into highly nonlinear systems by simply integrating a layer of 2D materials, leaping the device performance for ultrafast, all-optical communication devices. Finally, the challenges, opportunities, and perspectives in this field were provided.

"Ultrafast DLW is an indispensable tool to fabricate 2D material functional photonics devices with excellent performance." says the corresponding author Professor Baohua Jia from the research group, " Ultrafast lasers can drive a wide range of processes for the patterning and functionalization of 2D materials with a high resolution, accuracy and cost-effectiveness that can be used for scalable processing and realization of the next-generation high-performance portable, integratable, and flexible devices."

Combining the ultrafast DLW technique with the parallel writing and super-resolution methods, is promising to develop a novel laser fabrication platform enabling multifunctional and scalable 2D material integrated devices for multidisciplinary research and applications.


Ultrafast direct laser writing of 2D materials