An asymmetrical H-shaped resonator (ASH) has been designed using gold on a fused silica substrate. The aim is to
obtain a high - quality factor at the reflectance resonance peaks in the mid - infrared wavelength of 2 μm to 8 μm. The
structures were modelled using the Finite Difference Time Domain (FDTD) Lumerical Solution simulation software by
adjusting the parameter of periodic boundary condition on the X and Y-axis and perfectly matched layer (PML) on the
Z- axis. The asymmetric structures give double resonance peaks that depend on the arm-length of the structure. The
periodicity along the X and Y-axis was varied to tune the width of the resonant peaks in order to obtain the maximum Qfactor.
Experimental results broadly confirm the simulations.
The effects of two different type of asymmetric nano-antenna that produce distinct resonance peaks were experimentally and numerically observed. At mid-infrared wavelengths broad resonances based upon various metamaterials structures have been previously reported. Here we show that introducing a crossbar on vertical asymmetric dipole nano-antenna can produce narrower resonance peaks than the dipole alone. Our approach to investigating different asymmetric nanoantenna structures yielded quality factor values more than twice the existing values reported within this region of the electromagnetic spectrum.
We tune nanoantennas to resonate within mid-infrared wavelengths to match the vibrational resonances of C=C and C-H of the hormone estradiol. Modelling and fabrication of the nanoantennas produce plasmon resonances between 2 μm to 7 μm. The hormone estradiol was dissolved in ethanol and evaporated, leaving thickness of a few hundreds of nanometres on top of gold asymmetric split H-like shaped on a fused silica substrate. The reflectance was measured and a red-shift is recorded from the resonators plasmonic peaks. Fourier transform infrared spectroscopy is use to observe enhanced spectra of the stretching modes for the analyte which belongs to alkenyl biochemical group.
This presentation is concerned with nanophotonic structures, especially with arrays of asymmetric split-ring resonator (ASRR) structures, that may be exploited in a variety of sensing applications. These applications include bio-medical sensing, organic material sensing more generally - and environmental sensing. Specific attention has been paid to the identification of molecules of interest via their bond-resonance spectral signatures.
Recent advances have seen asymmetric split ring resonators (A-SRRs) developed as sensing elements to record a shift in their peaks when there is a corresponding change in the surrounding environment. These studies have led to the investigation of Fano resonances associated with the coupling of the resonances of the A-SRRs with the molecular resonances of the analyte. The hormone estradiol (E2) was dissolved in ethanol and evaporated, leaving thickness of a few hundreds of nanometres on top of gold A-SRRs on a silica substrate. The reflectance was measured and a red shift is recorded from the resonators plasmonic peaks. The geometric sizes of the ASRRs are calculated to tune the plasmonic resonances near the molecular resonance of the C-H stretch at nominally 3.33 microns. Corresponding Lumerical modelling of the experimental data is performed using only the intensity and wavelength to match the Fano resonance at modified wavelengths of 3.42 and 3.49 microns.
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