New technology can simplify the development of metasurfaces
A new technology for developing elements for information display devices was proposed by MIET scientists. According to them, the use of laser pulses will boost and cheapen the cost of the production of metasurfaces for new generation displays and various optical systems. The results of the study are published in Applied Surface Science journal.
The term "metasurfaces" refers to structures with a periodic pattern (structure) that can control electromagnetic waves, in particular light. Dielectric, metallic, and phase-alternating materials can be used as a base. The latter are able to change the phase state, and, as a result, the properties depending on external radiation.
Scientists are developing new compact devices on the basis of metasurfaces made of phase-alternating GST-material (i.e. compounds of the germanium, antimony and tellurium), that can display information using light waves. The devices include ultra-thin displays, augmented and virtual reality headsets and holographic projectors.
However, the process of nanostructuring the surface of the film for turning it into a multifunctional surface still is time-consuming and requires expensive lithography technology. For example, the necessary image of the metasurface must first be created on a template, and then transferred to the object in the selected resolution.
To reduce the cost of structuring films and to accelerate this process, MIET and a number of other universities such as IGIC RAS, MIPT, LPI and Herzen University use laser pulses instead of lithography.
"Using laser irradiation with ultrashort pulses made it possible to create ordered nanostructures on GST faster and more easily. To form a structured surface, we use pre-ablation processes, i.e., which precede the destruction of the material when exposed to a laser. The main advantage of this solution is that the pulses trigger the self-organization of structures on the surface, which means that they do not need to be "drawn", explained Sergey Kozyukhin, professor at the Institute of Advanced Materials and Technologies.
The scientist added that, depending on the intensity and/or number of pulses, three different types of structures can form, and the most curious of them are periodically arranged nanospheres of the same size. These are quite complex shapes to form, the radius of which can reach 150 nm.
Besides, previously it was not possible to obtain them in these materials without the use of additional technologies. Now, apart from the laser installation and the films themselves, no equipment is required to obtain nanospheres, Kozyukhin noted.
This technology makes it possible to develop highly ordered nanolenses and optical nanolattices, which in the future are supposed to be integrated into various optical systems, including information displays.
The research is carried out within the grant of the Russian Science Foundation at the facilities of the laboratory "Materials and Devices of Active Photonics" of MIET and supported by the federal program Priority-2030.