Optically Tunable Wavefunctions of Plasmonic Metals

Active plasmonics and nanophotonics are of great interest for fundamental science and applications of light.<br/>In our recent studies, we researched (i) effects of dye-doped polymers (Rh590:PMMA) on workfunction of Au and Ag [1,2] as well as (ii) effects of metal-dielectric substrates on photopolymerization of BITh molecules [3]. At this time, we report on control of the workfunctions of Ag and Au films coated with BITs by external light.<br/>Our samples were thin Ag and Au films deposited on glass and spin coated with BITh molecules. They were exposed to radiation of a broadband quartz lamp, which was a part of the Kevin Probe (KP) apparatus, and their workfunctions as well as the reflection spectra were studied using the Kelvin Probe and the spectrophotometer, respectively.<br/>We have found that in BITh-coated Ag and Au films, the workfunction decreased by several hundreds electron-volts during the photoexposure and almost returned to its original value when the light was turned off. The characteristic time scale of the process was ~15 minutes and it did not correlate with the rate of photopolymerization. (In particular, we did not see any reversibility of the photopolymerization.)<br/>As the workfunction is expected to affect the optical properties of metals and metal-based waveguides, the observed phenomenon paws the road to tunable Fabry-Perot resonators, Metal-Insulator-Metal (MIM) waveguides, and control of strong coupling of excitons with cavities and surface plasmons.<br/><br/>[1] Kanij Mehtanin Khabir, Mohammad Shahabuddin, Jalyn-Rose L. Clark, Natalia Noginova, Mikhail A. Noginov, “Workfunction studies of constituents of Fabri-Perot cavities and MIM waveguides”, 2022 MRS Spring Meeting and Exhibit, May 8 -13.; Honolulu, Hawaii, USA.<br/>[2] Kanij Mehtanin Khabir, Mohammad Shahabuddin, Jalyn-Rose L. Clark, Natalia Noginova, Mikhail A. Noginov, "Kelvin probe work-function studies of components of Fabry-Perot cavities and MIM waveguides," Proc. SPIE PC12195, Metamaterials, Metadevices, and Metasystems 2022, PC121951Z (3 October 2022); https://doi.org/10.1117/12.2635137<br/>[3] Leila Hesami, Chi Yang, Elias Anwar, Mikhail A. Noginov, “Effect of metal-dielectric environments on photopolymerization of the [2,2′-bi-1H-indene]-1,1′-dione-3,3′-diyldiheptanoatecarboxylate monomer”, 2022 MRS Spring Meeting and Exhibit, May 8 -13.; Honolulu, Hawaii, USA.