Electro-optically modulated lossy-mode resonance

Sensitivity, selectivity, reliability, and measurement range of a sensor are vital parameters for its wide applications. Fast growing number of various detection systems seems to justify worldwide efforts to enhance one or some of the parameters. Therefore, as one of the possible solutions, multi-domain sensing schemes have been proposed. This means that the sensor is interrogated simultaneously in, e.g., optical and electrochemical domains. An opportunity to combine the domains within a single sensor is given by optically transparent and electrochemically active transparent conductive oxides (TCOs), such as indium tin oxide (ITO). This work aims to bring understanding of electro-optically modulated lossy-mode resonance (LMR) effect observed for ITO-coated optical fiber sensors. Experimental research supported by numerical modeling allowed for identification of the film properties responsible for performance in both domains, as well as interactions between them. It has been found that charge carrier density in the semiconducting ITO determines the efficiency of the electrochemical processes and the LMR properties. The carrier density boosts electrochemical activity but reduces capability of electro-optical modulation of the LMR. It has also been shown that the carrier density can be tuned by pressure during magnetron sputtering of ITO target. Thus, the pressure can be chosen as a parameter for optimization of electro-optical modulation of the LMR, as well as optical and electrochemical responses of the device, especially when it comes to label-free sensing and biosensing.

Real-time Ultraviolet Radiation Sensor Based on Modified Cladding Optical Fibers Technology

In this work, the performance of single-mode optical fibers (SMFs) for ultraviolet (UV) radiation monitoring and dosimetry applications is presented. In particular, this work will focus on the Radiation-Induced Absorption (RIA) phenomena in the Near-Infrared domain (NIR). Such phenomena play a very important role in the sensing mechanism for SMF. Single mode fibers with a diameter of 50 µm were used for this purpose. These fibers were dipped into germanium (Ge) solution with different concentrations (1, 3, and 5 wt%) to produce the sensing part of the sensor. For all optical fiber sensors under investigation, the results indicated the dependence of the RIA on the applied UV radiation energy. Also, a redshift in peak wavelength was obtained. The influence of Ge concentration on sensing efficiency was studied and the best results were obtained with 3 wt% concentration as compared to 1 wt % and 5 wt % concentrations. The presented sensor shows good sensitivity to UV radiation which makes it possible to be applied in medical applications.

Hollow core negative curvature fiber based refractive index sensor design and investigation for tuberculosis monitoring

A myriad of pensile but pertinent issues found in the optical fiber sensors can be seeked resolution based on the antiresonant reflecting optical waveguide (ARROW) working principle. Due to its compact structure, the anti-resonance based sensor has several advantages such as high sensitivity response, low confinement loss, and high stability that make the sensor more effective for health monitoring. In this manuscript, an anti-resonance fiber sensor has been proposed for the detection of tuberculosis cells. An analytical structure has been explored to simulate the characteristics of the ARROW. For the suggested structure, the Finite Element Method (FEM) is used to conduct its numerical investigations. The proposed optical sensor working on the ARROW principle was implemented on the Comsol Multiphysics software. From the numerical analysis, it is noted that the designed sensor has reached around 99% sensitivity with negligible confinement loss and single modality due to the excellent light-guiding properties of the anti-resonance fiber. Besides, lots of optical parameters such as effective area, V-Parameter, spot-size along beam divergence have been calculated over the wide wavelength region. The achieved result indicates the various applications suitability of Antiresonant Hollow-Core Fiber (ARHCF) as a tuberculosis sensor.