Event Details

Surface enhanced Raman scattering (SERS) finds application in almost all fields of science and in the industry. Plasmonic nanostructures, e.g. a gold-coated AFM tip, localizes the source to nm-size hot spots which enables the enhancement of nonlinear effects like SERS. Even SERS have some limitations. When the source intensity increased, a Raman-active molecule can be damaged or its vibrational modes can be modified. In this presentation, I will introduce our recent method [1] which can increase the SERS signal about 1000 times, without increasing the hot spot intensity. The method relies on Fano resonances and necessitates the contamination of the AFM tip with appropriate auxiliary molecules. The method is easy to implement in experiments and will have great impact on the SERS imaging technology

I will also describe another new phenomenon. Once an AFM tip is manufactured, it operates in a certain wavelength range, e.g. 600 nm - 800 nm. I will show how we manage to operate it at other wavelengths, e.g. at 532 nm, via a similar method [2]. Moreover, in the scarce-contamination regime, this enables single-molecule-size resolution in SNOM. All the results are exact solutions of 3D Maxwell equations. I present textbook [3] results (very simple expressions) merely to anticipate/explain both phenomena.

References

- S. Postaci, B.C.Y. Karakul, Alpan Bek, M.E. Tasgin, Nanophotonics 7, 1687 - 1695 (2018)
- R. Sahin, M. Gunay, Alpan Bek, M.E. Tasgin, Ultra-high resolution aSNOM imaging at off-resonant wavelengths, arXiv:1807.07863
- M.E. Tasgin, Alpan Bek, S. Postaci, Fano resonances in the linear and nonlinear plasmonic response, Chapter 1 in, E. O. Kamenetskii, A. Sadreev, and A. Miroshnichenko (Editors), Fano resonances in optics and microwaves: Physics and application (2018), Springer Publishing.
Link to book