Square fractal-like nanoapertures for SEIRA spectroscopy: An analytical, numerical and experimental study


Aslan E., Turkmen M.

SENSORS AND ACTUATORS A-PHYSICAL, vol.259, pp.127-136, 2017 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 259
  • Publication Date: 2017
  • Doi Number: 10.1016/j.sna.2017.03.012
  • Title of Journal : SENSORS AND ACTUATORS A-PHYSICAL
  • Page Numbers: pp.127-136

Abstract

Due to the sensitivity limitations, infrared (IR) spectroscopy systems, in which conventional sensing platforms are used, have some problems with detecting the small quantities of molecules. By the advantages coming from their aperture based nature, nanoaperture arrays increase the light-matter interaction and can be useful to overcome some of these limitations. In this work, we propose an analytical, numerical and experimental study for a novel nanoaperture array which has enhanced transmission and reflection characteristics with high surface enhanced IR absorption (SEIRA) distributions. We numerically analyze the square fractal-like nanoapertures through the finite difference time domain method. Thus, we present a fine tuning mechanism for adjusting the resonance frequency which is highly desirable for SEIRA applications. We then propose analytical formulas for the resonance frequencies of the structures. Moreover, we experimentally realize the structure by using a high-precision and lift-off free nanofabrication method based on electron-beam lithography. Correspondingly, refractive index sensitivity analyses are performed by embedding our structure into different cladding media with several refractive index values. Finally, in order to show the SEIRA performance of the proposed nanoaperture array, we analyze the sensing characteristic of carbonyl nu(C=O) stretching mode in a thin poly(methyl methacrylate) (PMMA) film for a set of different film thicknesses. Due to the enhanced transmission and reflection behaviors with easily accessible ultra-high-field localization characteristics, the proposed sensing platform can be a good candidate for SEIRA spectroscopy and label-free bio sensing applications. (C) 2017 Elsevier B.V. All rights reserved.