We present the analysis for a Mach–Zehnder interferometer (MZI) mesh for refractive index sensing. We configure the mesh to be made from single-mode identical directional couplers forming coupled and cascaded MZIs. The design allows multiple input and output configurations yielding different intensity variations with refractive index at the output ports, thereby with more simultaneous measurements and improved estimate for the refractive index of a sample. The variation of intensity at the output ports due to fluctuations at the input and variation in coupling strengths of the directional couplers is incorporated in our estimates. This extensible and robust geometry should be useful for designing portable sensor configurations.

The existence of new types of four-wave mixing Floquet solitons were recently realized numerically through a resonant phase matching in a photonic lattice of type-I Dirac cones; specifically, a honeycomb lattice of helical array waveguides imprinted on a weakly birefringent medium. We present a wide class of exact solutions in this system for the envelope solitons in dark-bright pairs and a "molecular" form of bright-dark combinations. Some of the solutions, red or blue detuned, are mode-locked in their momenta, while the others offer a spectrum of allowed momenta subject to constraints amongst the system and solution parameters. We show that the characteristically different solutions exist at and away from the band edge, with the exact band edge possessing a periodic pair of sinusoidal excitations akin to that of two-level systems apart from localized solitons. These could have possible applications for designing quantum devices.

We demonstrate the precise variation of self-imaging distance with width of a Gaussian input, centrally fed into a symmetric dielectric slab waveguide of width ∼20λ0. The width of the Gaussian is varied from the paraxial to completely nonparaxial domain. Unlike the paraxial case, the self-imaging distance is found to depend on the beam width and change with the number of excited modes in the waveguide. These features should be useful in designing devices that exploit self-imaging for improved efficiency, especially in nanophotonic circuits.

The variation of focusing distance in a parabolic graded-index slab with the width of a one-dimensional Gaussian input fed at its waist, both axially and misaligned, into the waveguide is studied in paraxial and beyond-paraxial regimes. We obtain analytical expressions, scalable in terms of material parameters, for input coupling coefficients for such a Gaussian input. The focusing distance shows remarkable stability for an axially fed input for beam width exceeding the fundamental mode width of the waveguide. There is a smooth variation for the other regime of beam width. In the paraxial domain, we identify a unique beam width of ∼0.76 times the fundamental mode width for which the self-imaging distance is nearly independent of misalignment. The stability, a well-known sharp shift of the focusing point for an axially fed beam of width around that of the fundamental mode, and remarkable stability of self-imaging distance with misalignment at the unique beam width should be useful for efficiency enhancement of device interconnects, sensing, and lensing applications.

Composites of ZnFe2O4/La0.67Sr0.33MnO3 with different weight percentages were synthesized using sol-gel method and their magnetic behavior was investigated. Powder X-ray diffraction studies show spinel structure for zinc ferrite and rhombohedral for La0.67Sr0.33MnO3. An additional minor phase of α −Fe2O3 and ZnO was also noticed in zinc ferrite suggesting non-stoichiometric nature. Fourier transform infrared spectroscopy studies display cohabitation of two phases belonging to ferrite and perovskite phase with varying peak intensities. Field-dependent magnetization measurement at room temperature shows partial variation in saturation magnetization and remanent magnetization values with increase in La0.67Sr0.33MnO3 weight percent in zinc ferrite. Except for zinc ferrite, $\left (\frac {dM}{dH}\right )$ shows single peak with smooth variation, pointing to easy rotation of magnetic dipoles under applied fields.

This article presents the design of a real-time health monitoring system which can store a patient's basic health parameters. The data can be made available to a medical practitioner as an alert and for monitoring by multiple means of communication. At present, healthcare systems exist with single mode communication option – popularly either in GSM or data access on a web application. The proposed health monitoring system enhances healthcare delivery by communicating multiplexed data over three modes – BLE (mobile application), GSM (messaging services) and Wi-Fi (Internet).

We present a comparative study of the variation in dielectric relaxation for the additives SiO2, TiO2 and ZrO2 in cobalt ferrite. CoFe2O4 was prepared using microwave hydrothermal system and sintered at 900 °C/30 min using microwave sintering method. Real and imaginary parts of permittivity were measured in the frequency range of 1 MHz to 1.8 GHz for these samples. A shift in the dielectric relaxation towards higher frequencies for doped samples is observed as expected in percolating systems. A non-linear least square fit of the electron oscillator model is used to parameterize absorption in the samples.

Considering the Sub-1 GHz frequency as a solution to address the key requirements in wireless networks as it supports multiple nodes and covers longer distances in contrast to other existing and widely used wireless technologies like GSM, BLE, Bluetooth and WiFi. Consequently the Sub-1 GHz spectrum requires lower power from the transceiver than the 2.4 GHz band making it a great choice for battery operated IoT sensor devices. For deploying nodes to cover large area and long range, sensing devices must be small, energy efficient and cost effective. IoT Sensor devices using the Sub-1 GHz spectrum can handle interference better. The lower frequency ISM bands enable the Sub-1 GHz transmissions to weave better between buildings in an urban environment. This paper deals with the design and development of hardware as well as software of a Sub-1 GHz gateway and miniature sensor node for IoT applications. CC1310 SoC, a Sub-1 GHz family microcontroller is used in the design of Sub-1 GHz, 868 MHz board. (C) 2018 Elsevier B.V. All rights reserved.

Electronic and optical properties of wurtzite ZnO structure have been studied using first-principle density functional theory calculations by ELK package. We performed DFT+U calculations by selecting different Hubbard potentials U and J for Zn-3d and O-2p in order to tune the band gap to the desired value as of 3.3 eV that is comparable to experiments. The band gap value for ZnO has shown to be sensitive to the chosen Hubbard U and J potentials. In our DFT+U calculations, the original structure of w-ZnO was remained to be unaffected.

We investigate the effect of curvature of the tip and the convexity of an electrode on the localization of suspended particles under the combined effect of dielectrophoresis and AC electroosmosis through simulations using COMSOL Multiphysics. A systematic analysis of the parameters defining the convexity of the electrode—the radius of the tip and the apex angle shows that suspended particles can be trapped closely to the electrode edges for comparatively larger tip radii and apex angles. This in turn should favour the trapping of polarizable molecules between the electrodes only if the fluid velocities at the vortices are not very strong.

We study the electrolytic flow in a system of coplanar parallel electrodes subjected to an AC field. The model system has been thoroughly examined numerically for a large range of frequencies of the applied potential where we find a peak in the spectrum of the velocity magnitude at high frequencies along with exhibition of a pronounced peak at lower frequencies. Interestingly the first peak in the velocity spectrum shifts to lower frequencies while the second peak to higher frequencies with increasing distance from the electrode edge which suggests a formation of a non-planar electric double layer structure at higher frequencies.

We study the electroosmotic velocity of electrolyte in coplanar parallel electrodes. The velocity of the electrolyte measured at a certain point above the electrode shows a maximum as the frequency of the applied potential varies from ~1 Hz to 10 kHz which is within the approximation of a planar structure for electric double layer. We study an extended the range of applied frequency as it is plausible that interplay of various forces as well as the finite size of the ions would lead to a deviation from the simplification adopted in most theoretical models. In view of this, in the present study, the frequency range was extended to 80 kHz and a second maximum, albeit smaller by an order of magnitude, was also found, consistent with our apprehension. Moreover the variation of the velocity spectrum with respect to different viscosity and the conductivity of the materials have also been studied.

We show efficient electro-optic modulation in a subwavelength gap-plasmon waveguide (GPW) formed by an electro-optic polymer with metal coatings. The proposed device is studied in the attenuated total reflection and end-fire configurations. In dealing with the end-fire configuration we used a taper from a micron sized guide to the GPW. The structure is shown to exhibit large phase accumulation over short distances, controllable by the applied modulating voltage.

We study a critically coupled cavity doped with resonant atoms with metamaterial slabs as mirrors. We show how resonant atom-cavity interaction can lead to a splitting of the critical coupling dip. The results are explained in terms of the frequency and lifetime splitting of the coupled system.

We present a quantitative study of the effects of losses in layered media with a metamaterial layer as the constituent. The metamaterial is modelled by a causal isotropic effective medium (Lorentz-type) response. The parameters for the model are picked from a recent experiment. Two specific examples, namely, that of resonant tunnelling (RT) and imaging are chosen to demonstrate the devastating effects of losses in the present day metamaterials. It is then shown how large delays in RT, as well as near perfect imaging can be restored in gain-doped metamaterials. We also point out yet another use of metamaterials for achieving near perfect absorption, and its use for probing strong atom-field interaction.

We study critical coupling (CC) in a system of a dielectric layer sandwiched between two metamaterial layers leading to near-total suppression of both reflection and transmission at specified frequencies. The tunability of the CC frequency is demonstrated by varying the angle of incidence retaining the full causal response for the metamaterials.

We study resonant tunneling through a layered medium with a negative index medium (NIM) slab as a constituent layer. We demonstrate large delays in transmission mediated by the surface and the guided modes of the structure with low losses. We show how important it is to include NIM dispersion for correct assessment of the nature and magnitude of the delay. We also point out the role of NIM absorption for the feasibility of such compact delay devices.

We study critical coupling (CC) in a system of two coupled negative index medium (NIM) layers leading to near-total suppression of both reflection and transmission at specified frequencies. The tunability of the CC frequency is demonstrated by varying the angle of incidence retaining the full causal response for the NIM materials.

There are three recognized low-loss configurations for waveguide laser resonators in which the waveguide is either closed at each end by a plane mirror (dual case I design) or one of the plane mirrors is replaced by a curved mirror at some distance from the guide exit. Some time ago, a variant of the latter design was proposed by exploiting the self-imaging properties of multimode waveguides. The resonator was predicted to produce a TEM(00)-like output with very low round-trip loss and excellent mode discrimination even though the curved mirror was placed much nearer to the guide exit (making the resonator more compact) than was conventional for achieving those results. In the present work, we show that the desirable features of the above design can be achieved even in a dual case I configuration by using end mirrors with suitable reflectivity profiles. Since there is no free space region between the waveguide and the mirrors, the resonator will have the additional advantages of being compact and portable. Furthermore, the absence of curved mirrors will also facilitate its realization in semiconductor integrated optics technology.