Ramona Galatus

Performance Comparison of Two Sensors Based on Surface Plasmon Resonance in a Plastic Optical Fiber

In silica optical fiber Surface Plasmon Resonance (SPR)-based sensors, an increase in fiber core diameter produces a corresponding increase in the sensitivity and Signal to Noise Ratio (SNR). In Plastic Optical Fiber (POF) realized in PMMA there are different influences of design parameters on the performance, as both sensitivity and SNR are concerned. In particular, the SNR, for different refractive index values of the analyte, in a 250 μm diameter POF is greater than the one in 1,000 μm diameter POF. On the other hand, the sensitivity, for the same refractive index values of the analyte, in a 1,000 μm diameter POF is greater than the one in a 250 μm diameter POF. The results of an experimental analysis demonstrating the above behavior are reported.

Highly

The amplifying and filtering performance of a highly Yb/Er-codoped phosphate glass add-drop filter is numerically analyzed. The use of the microscopic statistical formalism to describe energy-transfer inter-atomic mechanisms allows determining realistic optimum parameters and working conditions. In order to optimize the device performance and achieve a significant signal power gain in both through and drop ports, in addition to a careful previous design, moderate input pump powers (>;50 mW) and comparatively high erbium concentrations (>;5 × 1026 m-3) are required. The optimal parameters present a strong dependence on the input pump power. This dependence confirms the necessity of considering the energy-transfer inter-atomic mechanisms for any optimization design process.

{\rm Yb}^{3+}/{\rm Er}^{3+}

Widespread use of antibiotics has led to pollution of waterways, potentially creating resistance among freshwater bacterial communities. Microorganisms resistant to commonly prescribed antibiotics (superbug) have dramatically increased over the last decades. The presence of antibiotics in waters, in food and beverages in both their un-metabolized and metabolized forms are of interest for humans. This is due to daily exposure in small quantities, that, when accumulated, could lead to development of drug resistance to antibiotics, or multiply the risk of allergic reaction. Conventional analytical methods used to quantify antibiotics are relatively expensive and generally require long analysis time associated with the difficulties to perform field analyses. In this context, electrochemical and optical based sensing devices are of interest, offering great potentials for a broad range of analytical applications. This review will focus on the application of magnetic nanoparticles in the design of different analytical methods, mainly sensors, used for the detection of antibiotics in different matrices (human fluids, the environmental, food and beverages samples).

-Codoped Waveguide Microring Resonator Optimized Performance

In this work an innovative and low cost optical chemical sensor, based on surface plasmon resonance in plastic optical fiber, is presented and experimentally tested for the detection and analysis of trinitrotoluene (TNT). The fabricated optical chemical sensor was realized removing the cladding of a plastic optical fiber along half the circumference, spin coating on the exposed core a buffer of Microposit S1813 photoresist, and finally sputtering a thin gold film. A Molecularly Imprinted Polymer (MIP) film was deposited on the thin gold film for the selective detection of TNT. It has been found that the sensor recognizes trinitrotoluene, since the SPR signal is affected by the presence of TNT in the polymer, while with a slow response kinetics, probably due to the thickness of the polymeric layer.

Magnetic Nanoparticles for Antibiotics Detection

The present work aims to provide a hybrid platform capable of complementary and sensitive detection of β-lactam antibiotics, ampicillin in particular. The use of an aptamer specific to ampicillin assures good selectivity and sensitivity for the detection of ampicillin from different matrice. This new approach is dedicated for a portable, remote sensing platform based on low-cost, small size and low-power consumption solution. The simple experimental hybrid platform integrates the results from the D-shape surface plasmon resonance plastic optical fiber (SPR-POF) and from the electrochemical (bio)sensor, for the analysis of ampicillin, delivering sensitive and reliable results. The SPR-POF already used in many previous applications is embedded in a new experimental setup with fluorescent fibers emitters, for broadband wavelength analysis, low-power consumption and low-heating capabilities of the sensing platform.

Detection of trinitrotoluene based on SPR in molecularly imprinted polymer on plastic optical fiber

The experimental results obtained with two different Plastic Optical Fiber (POF) geometries, tapered and not-tapered, for a sensor based on Surface Plasmon Resonance (SPR) are presented. SPR is used for determining the refractive index variations at the interface between a gold layer and a dielectric medium (aqueous medium). In this work SPR sensors in POF configurations, useful for bio-sensing applications, have been realized for the optimization of the sensitivity and experimentally tested. The results show as the sensitivity increases with the tapered POF configuration, when the refractive index of aqueous medium increases.

SPR based hybrid electro-optic biosensor for β-lactam antibiotics determination in water

Fluorescent optical fibers employ the luminescence property of fluorescent dyes in order to radiate light as a response to incident illumination. When multiple dyes are used to dope the fiber, fluorescence results from the energy transfer between the donor and acceptor dyes and the reabsorption process. In this work we propose a high-resolution distributed optical sensor for position monitoring developed around a yellow fluorescent fiber. Immunity vs. ambient light variations is achieved by employing the spectral behavior of the donoracceptor energy transfer mechanism and the reabsorption process. This consists in a red shift of the fiber emission peaks vs. distance. Extensive experimentation with the laboratory proof of principle validates the proposed solution. Measurements carried out in laboratory environment under ambient illumination show that the wavelength of the emission peaks is insensitive to the intensity of the incident light, but is dependent on the variation of the ambient light color. Accordingly, rather than monitoring the wavelengths of the emission peaks, the proposed positions sensor evaluates the spectral spacing between the peaks. This provides an accurate estimate of the distance between the fiber end and the incident light application point. The proposed sensor exhibits a monotonous decrease of the spectral spacing vs. distance, which is indeed insensitive to limited variation of the ambient light.

Experimental results for characterization of a tapered plastic optical fiber sensor based on SPR

We present a new experimental investigation about the possibility to use fluorescent optical fibers as light sources, instead of halogen lamps, for plasmonic sensing. The novel configuration has been first introduced, and then the components’ properties and the experimental results have been illustrated. Two sensor systems have been realized and characterized by exploiting red and blue fluorescent optical fibers to illuminate different plasmonic sensors and observe the transmitted spectra by a spectrometer. In particular, the plasmonic sensors have been realized with two different metals, gold and silver, sputtered on D-shaped plastic optical fibers (POFs) with an optical buffer layer between the metal film and the POF core. We have matched the metal’s plasmonic resonance wavelength with the emission of a specific fluorescent optical fiber. The good quality of the experimental results, the low-power consumption, the low cost, the remote sensing capability, the small size, and the simple scheme of the configuration make this strategy a potentially suitable diagnostic tool for biosensing applications.

Fluorescent fiber implementation of a high-resolution distributed position sensor

A comparative analysis of two optical fiber sensing platforms is presented. The sensors are based on surface plasmon resonance (SPR) in a D-shaped plastic optical fiber (POF) with a photoresist buffer layer between the exposed POF core and the thin gold film. We show how the sensors performances change when the photoresist layer changes. The photoresist layers proposed in this analysis are SU-8 3005 and S1813. The experimental results are congruent with the numerical studies and it is instrumental for chemical and bio-chemical applications. Usually, the photoresist layer is required in order to increase the performance of the SPR-POF sensor.

Plasmonic Sensing in D-Shaped POFs With Fluorescent Optical Fibers as Light Sources

The optimized geometry based on high-order active microring resonators (MRR) geometry is proposed. The solution possesses both the filtering and amplifying functions for the signal at around 1534nm (pump 976 nm). The cross-grid resonator with laterally, series-coupled triple-microrings, having 15.35μm radius, in a co-propagation topology between signal and pump, is the structure under analysis (commonly termed an add-drop filter).