In this study, we present the optical properties of a plasmonic nanoantenna array based on H-shaped gold nanoparticles with extended arms, which can be used for infrared detection applications. Plasmonic nanoantennas operating at the infrared and visible region provide a unique way to capture, control and manipulate light at the nanoscale through the excitation of collective electron oscillations known as surface plasmons. The unit cell of proposed antenna consists of one H-shaped nanostructure and two extended arms located on the lateral sides of this nanostructure. We will demonstrate the proposed antenna has a dual band spectral response and the locations of the resonance frequencies can be adjusted by changing the geometrical dimensions of both the H-shaped nanoparticles and the extended arms. Theoretical calculations of the reflectance spectra of the nanoantenna array are performed by using simulation software, which utilizes Finite Difference Time Domain (FDTD) method. In order to show the sensing capacity of the structure, the effect of the dielectric medium on the resonance frequency is also determined. The results show that the proposed antenna can be utilized for infrared sensing applications.
Recent advances in nanofabrication and computational electromagnetic design techniques have enabled the realization of metallic nanostructures in different shapes and sizes with adjustable resonance frequencies. To date, many metamaterial designs in various geometries with the used of different materials have been presented for the applications of surface plasmons, cloaking, biosensing, and frequency selective surfaces1-5. Surface plasmons which are collective electron oscillations on metal surfaces ensure that plasmonic nanoantennas can be used in many applications like biosensing at infrared (IR) and visible regions. The nanostructure that we introduce has a unit cell that consists of Jerusalem crossshaped nanoaperture on a gold layer, which is standing on suspended SiNx, Si or glass membranes. The proposed nanoaperture antenna array has a regular and stable spectral response. In this study, we present sensitivity of the resonance characteristics of Jerusalem cross-shaped nanoaperture antenna arrays to the changes in substrate parameters and metal thickness. We demonstrate that resonance frequency values can be adjusted by changing the thicknesses and types of the dielectric substrate and the metallic layer. Numerical calculations on spectral response of the nanoantenna array are performed by using Finite Difference Time Domain (FDTD) method6. The results of the simulations specify that resonance frequencies, the reflectance and transmittance values at resonances, and the band gap vary by the change of substrate parameters and metal thicknesses. These variations is a sign of that the proposed nanoantenna can be employed for sensing applications.
We demonstrate a composite metamaterial composed of two asymmetrically oriented π-shaped structures that
exhibits plasmonic analogue of electromagnetically induced transparency (EIT). The structure exhibits fine
tuning of EIT-like spectral behavior and spatial control of near-field intensity distribution. Originated from the
asymmetric design, we introduce a more compact system which possesses the similar EIT-like spectral response
as well as much smaller optical mode volumes.
KEYWORDS: Antennas, Metamaterials, Near field, Plasmonics, Nanolithography, Optical properties, Electron beam lithography, Reactive ion etching, Scanning electron microscopy, Optical filters
In this paper, we present numerical and experimental results on optical properties of a multi-resonant UT-shaped
plasmonic nanoaperture antenna for enhanced optical transmission and near-field resolution. We propose different
structure designs in order to prove the effect of geometry on resonance spectrum and near-field enhancement.
Theoretical calculations of transmission spectra and field distributions of UT-shaped nano-apertures are performed by
using three-dimensional finite-difference time-domain method. The results of these numerical calculations show that
transmission through the apertures is indeed concentrated in the gap region. In addition to theoretical calculations, we
also performed a lift-off free plasmonic device fabrication technique based on positive resist electron beam lithography
(EBL) and reactive ion etching in order to fabricate UT-shaped nanostructures. For further confirmation of the multiresonant
behavior, we checked the individual U-and T-shaped nano-aperture antenna responses. We also studied the
parameter dependence of the structure to determine the control mechanism of the spectral response. Theoretical
calculations are supported with experimental results to prove the enhanced field distribution and multi-resonant behavior
which can be suitable for infrared detection of biomolecules, wavelength-tunable filters, optical modulators, and ultrafast
switching devices.teInp
KEYWORDS: Antennas, Metamaterials, Nanolithography, Near field optics, Transmittance, Metals, Electron beam lithography, Nanostructures, Near field, Optical resolution
The subject of light transmission through optically thin metal films perforated with arrays of subwavelength nanoholes
has recently attracted significant attention. In this work, we present experimental and calculated results on optical
transmission/reflection of the U-shaped nanoapertures for enhanced optical transmission and resolution. We propose
different structure designs in order to prove the effect of geometry on resonance and enhanced fields. Theoretical
calculations of transmission/reflection spectra and field distributions of U-shaped nano-apertures are performed by using
3-dimensional finite-difference time-domain method. The results of these numerical calculations show that transmission
through the apertures is indeed concentrated in the gap region. Added to theoretical calculations we also performed a liftoff
free plasmonic device fabrication technique based on positive resist electron beam lithography and reactive ion
etching in order to fabricate U-shaped nanostructures. After transferring nanopattern on 80 nm thick suspended SiNx
membrane using EBL followed by dry etching, a directional metal deposition processes is used to deposit 5 nm thick Ti
and 30 nm thick Au layers. Theoretical calculations are supported with experimental results to prove the tunability of
resonances with the geometry at the mid-infrared wavelengths which could be used for infrared detection of
biomolecules.
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