Browsing by Author "Zhang, Kunyi"
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Item Plasmonic nanoarcs: a versatile platform with tunable localized surface plasmon resonances in octave intervals(Optical Society of America Publishing, 2020-10-12) Zhang, Kunyi; Lawson, Andrew P.; Ellis, Chase T.; Davis, Matthew S.; Murphy, Thomas E.; Bechtel, Hans A.; Tischler, Joseph G.; Rabin, OdedThe tunability of the longitudinal localized surface plasmon resonances (LSPRs) of metallic nanoarcs is demonstrated with key relationships identified between geometric parameters of the arcs and their resonances in the infrared. The wavelength of the LSPRs is tuned by the mid-arc length of the nanoarc. The ratio between the attenuation of the fundamental and second order LSPRs is governed by the nanoarc central angle. Beneficial for plasmonic enhancement of harmonic generation, these two resonances can be tuned independently to obtain octave intervals through the design of a non-uniform arc-width profile. Because the character of the fundamental LSPR mode in nanoarcs combines an electric and a magnetic dipole, plasmonic nanoarcs with tunable resonances can serve as versatile building blocks for chiroptical and nonlinear optical devices.Item Remote Chemical Sensing by SERS with Self-Assembly Plasmonic Nanoparticle Arrays on a Fiber(Frontiers Media, 2022-01-25) Zhang, Xin; Zhang, Kunyi; von Bredow, Hasso; Metting, Christopher; Atanasoff, George; Briber, Robert M.; Rabin, OdedAn optical fiber was modified at the tip with a self-assembled plasmonic metamaterial that acts as a miniature surface-enhanced Raman spectroscopy (SERS) substrate. This optical fiber-based device co-localizes the laser probe signal and the chemical analyte at a distance remote from the spectrometer, and returns the scattered light signal to the spectrometer for analysis. Remote SERS chemical detection is possible in liquids and in dried samples. Under laboratory conditions, the analyte SERS signal can be separated from the background signal of the fiber itself and the solvent. An enhancement factor greater than 35,000 is achieved with a monolayer of the SERS marker 4-aminothiophenol.Item TAILORING LOCALIZED SURFACE PLASMON RESONANCES IN METALLIC NANOANTENNAS(2020) Zhang, Kunyi; Rabin, Oded; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The strong localized electromagnetic field achievable with metallic nanoantennas provides new opportunities for harmonics generation and label-free chemical sensing. In this work, the localized surface plasmon resonances (LSPRs) of metallic nanoarcs on dielectric substrates have been systematically investigated with visible and infrared spectroscopy, with the goal of elucidating the relationship between the structural and material parameters of the nanoarcs and their resonances. The transmission spectra provide rich information regarding the fundamental and higher order LSPR modes. Experimental results and numerical simulations demonstrate that the LSPR wavelengths are governed by the mid-arc length of the nanoarcs, and the extinction cross-sections of the different order modes are controlled by the central angle of the nanoarc and the symmetry of the mode. The fundamental and second order LSPR wavelengths can be tuned independently through the design of a non-uniform arc-width profile. Several relationships between features of the LSPR modes and the geometric parameters of nanoarcs are also confirmed by transformation optics analysis. The newly found relationships are then utilized as guidelines for the realization of plasmonic nanoarc antennas exhibiting efficient second harmonic generation (SHG). In another application, strong coupling between LSPRs and molecular vibrations is evident in the IR spectra of plasmonic nanoarcs placed in contact with a thin film of polymer, a native oxide layer or a thiol monolayer, enhancing the vibrational mode signals. This observation suggests that by appropriately tuning the frequency of the LSPR modes, the localized electromagnetic field around nanoarcs can resonantly couple to another emitter to boost its far-field radiation, which could benefit applications requiring highly localized, sensitive and selective chemical detection.