Fabrication-friendly polarization-sensitive plasmonic grating for optimal surface-enhanced Raman spectroscopy

Journal of the European Optical Society-Rapid Publications

Harri Lipsanen¹  Antti Matikainen¹  J. Jussi Toppari²  Arpan Dutta²  Eero Hulkko³  Khairul Alam⁴  Tarmo Nuutinen⁵  Guoguo Kang⁶  Peng Li⁶ 

[1] Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland;Department of Physics and Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland;Department of Physics and Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland;Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland;Institute of Photonics, University of Eastern Finland (UEF), Joensuu, Finland;Institute of Photonics, University of Eastern Finland (UEF), Joensuu, Finland;Department of Environmental and Biological Sciences, UEF, Joensuu, Finland;School of Optoelectronics, Beijing Institute of Technology, Beijing, China;

关键词: Plasmonic grating;    Surface-enhanced Raman scattering;    Fill factor;   

DOI  :  10.1186/s41476-020-00144-5

来源: Springer

【 摘 要 】

Plasmonic nanostructures are widely utilized in surface-enhanced Raman spectroscopy (SERS) from ultraviolet to near-infrared applications. Periodic nanoplasmonic systems such as plasmonic gratings are of great interest as SERS-active substrates due to their strong polarization dependence and ease of fabrication. In this work, we modelled a silver grating that manifests a subradiant plasmonic resonance as a dip in its reflectivity with significant near-field enhancement only for transverse-magnetic (TM) polarization of light. We investigated the role of its fill factor, commonly defined as a ratio between the width of the grating groove and the grating period, on the SERS enhancement. We designed multiple gratings having different fill factors using finite-difference time-domain (FDTD) simulations to incorporate different degrees of spectral detunings in their reflection dips from our Raman excitation (488 nm). Our numerical studies suggested that by tuning the spectral position of the optical resonance of the grating, via modifying their fill factor, we could optimize the achievable SERS enhancement. Moreover, by changing the polarization of the excitation light from transverse-magnetic to transverse-electric, we can disable the optical resonance of the gratings resulting in negligible SERS performance. To verify this, we fabricated and optically characterized the modelled gratings and ensured the presence of the desired detunings in their optical responses. Our Raman analysis on riboflavin confirmed that the higher overlap between the grating resonance and the intended Raman excitation yields stronger Raman enhancement only for TM polarized light. Our findings provide insight on the development of fabrication-friendly plasmonic gratings for optimal intensification of the Raman signal with an extra degree of control through the polarization of the excitation light. This feature enables studying Raman signal of exactly the same molecules with and without electromagnetic SERS enhancements, just by changing the polarization of the excitation, and thereby permits detailed studies on the selection rules and the chemical enhancements possibly involved in SERS.

【 授权许可】

CC BY