Exploring the Absorption Spectra of an Ultra-Wideband Metamaterial Absorber in the Visible and Near-Infrared Regions.

This paper investigates the absorption spectra of a plasmonic metamaterial absorber in the visible and near-infrared regimes by utilizing a metal-dielectric-metal (MDM) functional stack. A periodic metal-dielectric cap is introduced on top of a metallic substrate to excite surface plasmon modes. The shape of this cap and the glass coating modifies the absorbance bandwidth. Although the circular cap exhibits less broadening in the absorbance than the square one, the circular cap's glass coating boosts the bandwidth's expansion in the near-infrared region to about 1.65 µm. In the visible and near-infrared regimes, absorption bandwidth and spectral ratio can be tailored by modifying four distinct structural parameters. The finding shows that one can achieve an ultra-broad bandwidth that extends from 0.3 µm to 1.65 µm at 90% absorbance. The thickness of the top titanium layer, the silicon dioxide spacer thickness, the Ti-SiO2 cap diameter, and the sliver substrate pitch are selected to be 20 nm, 60 nm, 215 nm, and 235 nm, respectively. Furthermore, the influence of using various metals on absorption spectra has been explored in the visible and near-infrared regimes. The d metals considered for the top layer are titanium, nickel, chromium, silver, copper, gold, aluminum, and gold.

Investigating the Absorption Spectra of a Plasmonic Metamaterial Absorber Based on Disc-in-Hole Nanometallic Structure.

In this work, we present and explore the characteristics of a plasmonic metamaterial absorber based on a metal-insulator-metal functional stack. The proposed structure consists of glass "sandwiched" between a silver reflector and a titanium metallic disc, embedded inside a Ti periodic nano-hole array, as an outside layer. In the visible and infrared regimes, the optical absorption spectra of such structures have been investigated using the finite difference time domain method. The impact of modifying nano-hole and embedded disc diameters on the absorber's performance has been investigated. Changing these two distinct structural parameters tunes the coupling effect between the localized and propagating surface plasmons. The adequate bandwidth, average spectral absorption rate, and short circuit current density are calculated to determine the performance of the designated absorber. The proposed structure of the plasmonic metamaterial absorber reaches an average absorption of over 94% in a bandwidth of 0.81 µm and near-perfect absorption of 98% around the wavelength of 0.7 µm, with an almost 100% relative absorption bandwidth and 41 mA/cm2 short circuit current density. In addition, the results show that the disc-in-hole absorber's structural parameters can be changed precisely and facilely to tailor to the absorption spectra.

Plasmon-Enhanced Sunlight Harvesting in Thin-Film Solar Cell by Randomly Distributed Nanoparticle Array.

In this paper, a randomly distributed plasmonic aluminum nanoparticle array is introduced on the top surface of conventional GaAs thin-film solar cells to improve sunlight harvesting. The performance of such photovoltaic structures is determined through monitoring the modification of its absorbance due to changing its structural parameters. A single Al nanoparticle array is integrated over the antireflective layer to boost the absorption spectra in both visible and near-infra-red regimes. Furthermore, the planar density of the plasmonic layer is presented as a crucial parameter in studying and investigating the performance of the solar cells. Then, we have introduced a double Al nanoparticle array as an imperfection from the regular uniform single array as it has different size particles and various spatial distributions. The comparison of performances was established using the enhancement percentage in the absorption. The findings illustrate that the structural parameters of the reported solar cell, especially the planar density of the plasmonic layer, have significant impacts on tuning solar energy harvesting. Additionally, increasing the plasmonic planar density enhances the absorption in the visible region. On the other hand, the absorption in the near-infrared regime becomes worse, and vice versa.

Fiber-based simultaneous mode and wavelength demultiplexer.

We theoretically design and analyze the performance of a fiber-based linearly polarized (LP) mode demultiplexer using a Fabry-Perot interferometer. The all-fiber geometry of the reported demultiplexer is obtained by writing fiber Bragg gratings (FBGs) in a few-mode fiber (FMF), such that the FBGs act as partial reflecting mirrors for the LP modes. We also demonstrate the ability to decompose a received optical signal into its individual LP components in wavelength-division multiplexing networks.

Ultra-Sensitive Nano Optical Sensor Samarium-Doxycycline Doped in Sol Gel Matrix for Assessment of Glucose Oxidase Activity in Diabetics Disease.

A low cost and very sensitive method for the determination of the activity of glucose oxidase enzyme in different diabetics serum samples was developed. The method based on the assessment of the H2O2 concentration produced from the reaction of the glucose oxidase (GOx) enzyme with glucose as substrate in the serum of diabetics patients by nano optical sensor Sm-doxycycline doped in sol gel matrix. H2O2 enhances the luminescence intensity of all bands of the nano Sm-doxycycline complex [Sm-(DC)2]+ doped in sol-gel matrix, especially the 645 nm band at λex = 400 nm and pH 7.0 in water. The influence of the different analytical parameters that affect the luminescence intensity of the nano optical sensor, e.g. pH, H2O2 concentration and foreign ions concentrations were studied. The remarkable enhancement of the luminescence intensity of nano optical sensor [Sm-(DC)2]+ complex in water at 645 nm by the addition of various concentrations of H2O2 was successfully used as an optical sensor for the assessment of the activity of the glucose oxidase enzyme in different diabetics serum samples. The calibration plot was achieved over the activity range 0.1-240 U/L with a correlation coefficient of 0.999 and a detection limit of 0.05 U/L.

Investigating the characteristics of TM-pass/TE-stop polarizer designed using plasmonic nanostructures.

Plasmonics-based polarizers are important for many photonic devices and applications. In this paper, we design and investigate the characteristics of a new TM-pass/TE-stop polarizer using silver nanograting of exponentially tapered slit sidewalls. Performance of the designed polarizer is determined through monitoring the modification of its insertion loss, return loss, extinction ratio, and far-field transform due to changing its structural parameters. We find that the structural parameters of the reported polarizer such as a slit sidewall tapering coefficient and slit opening widths have a significant impact on tuning the polarizer characteristics.