Researchers of Center for Physical Sciences and Technology dr. Evaldas Stankevičius, Kernius Vilkevičius, dr. Mindaugas Gedvilas, Ernesta Bužavaitė-Vertelienė, prof. Algirdas Selskis and prof. Zigmas Balevičius published a scientific publication “Direct Laser Writing for the Formation of Large-Scale Gold Microbumps Arrays Generating Hybrid Lattice Plasmon Polaritons in the Vis-NIR Range” in the prestigious journal Advanced Optical Materials (web link: https://onlinelibrary.wiley.com /doi/10.1002/adom.202100027).
The aim of the research was to form a large-scale grating generating hybrid lattice plasmon polaritons in the Vis-NIR Range. The article demonstrates that the peak of hybrid lattice plasmon resonance depends on the period of the fabricated arrays, the thickness of the gold film, coupled light polarization, and sample orientation. The key element of each grating is a hollow gold microbump that is formed by exposing a thin gold coating with a tightly focused laser beam.
a) Illustration of Au bumps formation in a thin gold film using direct laser writing technique; b) and c) SEM micrographs of fabricated gold bumps array in a thin gold film (50 nm) with different magnification; d) cross-section of gold bumps.
Gratings fabricated using direct laser writing technique.
According to dr. Evaldas Stankevičius, due to the extremely small dimensions of periodic surface irregularities, the production of gratings that excite hybrid plasmonic modes in the visible and near-infrared region is complicated and expensive. Typically, such gratings are produced using lithography. In this work, we have demonstrated that our used laser technology can be a great alternative to lithographic methods. In our case, the grating is formed by single-pulse laser irradiation of a thin gold film. The coating irradiation by a tightly focused laser beam leads to the formation of a gold microbump, which is a key element of the grating. Our used method is much more efficient compared to lithography because the grating is formed directly on the gold coating without the use of expensive vacuum-supporting equipment.
The structures generating hybrid plasmonic modes have a higher optical sensitivity, so their possible practical application is quite wide. Due to their compactness, such gratings can be widely used in biosensors for the detection of tumors, antigens, allergens in food, for the study of drugs and proteins, for cellular processes, or the monitoring of adsorption and desorption kinetics of different molecules. Besides, due to the optical properties of the formed gratings, they can be used in microscopy, surface-enhanced Raman spectroscopy, or the development of plasmonic nanolasers.
Acknowledgments: Dr. Evaldas Stankevičius and Kernius Vilkevičius acknowledge the Agency for Science, Innovation and Technology (MITA, Lithuania) for the financial support of project No. 01.2.2-MITA-K-702-09-0017.