We present a relative sensitivity of in-fiber inter-cross demodulation of a Mach- Zehnder interferometer (MZI) based on an etched Multi-core fiber (eMCF). The sensor can measure the external refractive index (RI) and temperature with a large fringe visibility of 15dB. It is tuned using a simple technique of slow chemical etching. When the outer cores of MCF will be exposed to the surrounding, a large difference of relative effective RI is observed, which enhances the sensitivity of the sensor. The sensor's wavelength and intensity responses have displayed that it can function with three different inter-cross-demodulation phenomena. A superior RI sensitivity of 178.20 dB/RIU in the range of 1.334 to 1.370, and temperature sensitivity of 66.73 pm/°C in the range of 30 to 80 °C are obtained, with an adequate linear response. Besides, it can readily resolve the issues of cross-sensitivity. Moreover, it has many advantages including easy fabrication, compact size, multiplex, repeatable, stable and can easily differentiate RI and temperature, which lack others.

In this paper, we present an ultrawideband reflective metasurface with the properties of an LTC-PC, which is an orthotropic composition with two mutually orthogonal symmetric axes, v and u, and 45° rotation about the vertical y-axis. Based on the metasurface unit cell, it seems like a circular pie embedded with a rectangular patch. The converter can convert LP electromagnetic (EM) waves to CP waves over the bands from 20.18 GHz to 33.93 GHz, with a 3-dB AR bandwidth of up to 50.8% and a circular polarization wave that is RHCP (right hand CP). Moreover, the linear-to-circular PCR exceeds 98% in the frequency bands of 20–34 GHz. A comprehensive theoretical investigation was conducted to determine the fundamental cause of the LTC polarization conversion. The $∆{\phi }_{uv}$ between two reflection coefficients at v- and u-polarized incidences is ±90°, which fully anticipates the axial ratio of the reflected wave. Any reflective metasurface can be used as an efficient LTC-PC if the $∆{\phi }_{uv}$ is close to ±90°.

A highly sensitive strain sensor based on tunable cascaded Fabry–Perot interferometers (FPIs) is proposed and experimentally demonstrated. Cascaded FPIs consist of a sensing FPI and a reference FPI, which effectively generate the Vernier effect (VE). The sensing FPI comprises a hollow core fiber (HCF) segment sandwiched between single-mode fibers (SMFs), and the reference FPI consists of a tunable air reflector, which is constituted by a computer-programable fiber holding block to adjust the desired cavity length. The simulation results predict the dispersion characteristics of modes carried by HCF. The sensor’s parameters are designed to correspond to a narrow bandwidth range, i.e., 1530 nm to 1610 nm. The experimental results demonstrate that the proposed sensor exhibits optimum strain sensitivity of 23.9 pm/με, 17.54 pm/με, and 14.11 pm/με cascaded with the reference FPI of 375 μm, 365 μm, and 355 μm in cavity length, which is 13.73, 10.08, and 8.10 times higher than the single sensing FPI with a strain sensitivity of 1.74 pm/με, respectively. The strain sensitivity of the sensor can be further enhanced by extending the source bandwidth. The proposed sensor exhibits ultra-low temperature sensitivity of 0.49 pm/°C for a temperature range of 25 °C to 135 °C, providing good isolation for eliminating temperature–strain cross-talk. The sensor is robust, cost-effective, easy to manufacture, repeatable, and shows a highly linear and stable response for strain sensing. Based on the sensor’s performance, it may be a good candidate for high-resolution strain sensing.

A mathematical model of random cylinder is given to facilitate realization of a single random cylinder and study its electromagnetic scattering properties. The proposed model is very versatile as c...

The investigation of core-shell nanoparticles has been greatly exciting in biomedical applications, as this remains of prime importance in targeted drug delivery, sensing, etc. In the present work, the polarizability and scattering features of nanoparticles comprised of nano-sized dielectric/metallic core-shell structures were investigated in the fractional dimensional (FD) space, which essentially relates to the confinement of charged particles. For this purpose, three different kinds of metals—namely aluminum, gold and silver—were considered to form the shell, having a common silicon dioxide (SiO₂) nanoparticle as the core. It is noteworthy that the use of noble metal-SiO₂ mediums interface remains ideal to realize surface plasmon resonance. The core-shell nanoparticles were considered to have dimensions smaller than the operating wavelength. Under such conditions, the analyses of polarizability and the scattering and absorption cross-sections, and also, the extinction coefficients were taken up under Rayleigh scattering mechanism, emphasizing the effects of a varying FD parameter. Apart from these, the tuning of resonance peaks and the magnitude of surface plasmons due to FD space parameter were also analyzed. It was found that the increase of FD space parameter generally results in blue-shifts in the resonance peaks. Apart from this, the usage of gold and silver shells brings in fairly large shifts in the peak positions of wavelengths, which allows them to be more suitable for a biosensing purpose.