Resonant modes of reflecting gratings engineered for multimodal sensing
Mohammad Abutoama,
Aabha Bajaj,
Dong Li,
Yawen Wang,
Lin Jiang,
Ibrahim Abdulhalim
Affiliations
Mohammad Abutoama
Department of Electrooptics and Photonics Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, School of Electrical and Computer Engineering, Ben Gurion University, Beer Sheva 84105, Israel
Aabha Bajaj
Department of Electrooptics and Photonics Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, School of Electrical and Computer Engineering, Ben Gurion University, Beer Sheva 84105, Israel
Dong Li
Institute of Functional Nano and Soft Materials Laboratory (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, China
Yawen Wang
Institute of Functional Nano and Soft Materials Laboratory (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, China
Lin Jiang
Institute of Functional Nano and Soft Materials Laboratory (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, China
Ibrahim Abdulhalim
Department of Electrooptics and Photonics Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, School of Electrical and Computer Engineering, Ben Gurion University, Beer Sheva 84105, Israel
Reflecting gratings with narrow grooves exhibit multiple electromagnetic modes. Using a simple setup, surface plasmon (SP), cavity mode (CM) resonance shift, surface-enhanced fluorescence (SEF), and surface-enhanced Raman scattering signals can be measured, thus forming a multimodal sensing or imaging system. The nature of these modes is first analyzed using dispersion curves as a function of the wavelength, thickness, and period and then confirmed experimentally. For a thin (20 nm) enough grating, the resonant modes are shown to be mainly attributed to SP excitation. Increasing the grating thickness allows the excitation of CMs, and more importantly, coupling between the two resonant modes can take place under certain conditions, leading to a change in the sign of the radius of curvature of the CM branch near the SP wavelength. Field distribution calculations show an agreement with the dispersion curve analysis expressing the nature of the three mode field. Additionally, the SP wavelength was shown to separate between the cavity and diffraction mode branches. The resonant modes can be controlled by tuning the grating parameters and are shown to be spread over a wide spectral range. Experimental verification (sensing in the visible and infrared ranges and SEF experiments) of the observed phenomena is performed on a 154 nm thick silver grating with 1050 nm period fabricated using electron beam lithography. Multimodal systems are important to provide as much as possible information on the measured samples, such as the concentration of analytes and characterization of cells and tissue.
