Presentation Information
[9p-PB7-6]Evaluation of Plasmonic Tapered Structures for Broadband Plasmon Nanofocusing toward Raman Spectroscopic Applications
〇(M2)Yuto Okamura1, Prabhat Verma1, Takayuki Umakoshi1 (1.UOsaka)
Keywords:
Plasmonics,Raman spectroscopy
Plasmon nanofocusing is a technique that generates highly confined optical fields by propagating and compressing plasmons along a metallic tapered structure. Unlike conventional plasmonic approaches based on localized plasmon resonance, plasmon nanofocusing offers broadband operation over a wide wavelength range, making it attractive for various nanophotonic applications. One promising application is Raman spectroscopy, where enhanced optical fields can improve the sensitivity of molecular analysis.In this study, we investigate metallic tapered structures for broadband plasmon nanofocusing toward Raman spectroscopic applications. Silver and aluminum tapered structures were fabricated using thin-film deposition and focused ion beam milling. Their performances were evaluated using excitation wavelengths of 442, 532, 633, and 785 nm. While silver structures provided strong Raman enhancement, stable plasmon nanofocusing at 442 nm was difficult to achieve and the structures were susceptible to oxidation. In contrast, aluminum structures enabled stable plasmon nanofocusing across all excitation wavelengths, including 442 nm, owing to their favorable plasmon propagation characteristics in the short-wavelength region. However, aluminum exhibited weaker fluorescence quenching, resulting in increased fluorescence background during Raman measurements.By comparing the advantages and limitations of silver and aluminum tapered structures, this work provides insights into material selection and design strategies for broadband plasmon-nanofocusing-based Raman spectroscopy.