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A micrometer size, simple, and low-cost sensor for continuous monitoring of human blood during malarial infection at its various stages is proposed in this work. The sensor comprises a light source, silica fiber directional coupler, and an optoelectronic photodetector. The sensor is simulated for fiber diameters from 1–1.8 #x03BC;m and optimization is done. The sensor produces a photocurrent of a few mA, which gives the level of infection. It can detect a change in refractive index, of the order of 10−5, and needs a small sensing length of a few μm. It can be potentially built as an integrated embedded device.

In the present work, a miniature optical gas sensor for the leakage detection of propane is proposed. It is constructed by employing single mode silica nanowire Mach–Zehnder interferometer (MZI). Suitable chemical treatment of silica nanowire for propane gas adsorption onto it is suggested. In the proposed sensor, the idea is that, the propane gas gets adsorbed on treated surface of silica nanowire, which changes the refractive index of few nanometer thick layer on the nanowire surface. In theoretical modeling and simulation, full vectorial analysis of two and three layers tightly guiding waveguide structures are presented. Simulations include calculation of phase difference at the output end of MZI, phase sensitivity, detection limit and measurable refractive index over a practicable sensing length such as 1 mm. Sensing characteristics are numerically investigated. The sensor shows merits over conventional gas sensors. The sensing characteristics show negligible dependence on temperature, vibration and humidity, which is discussed in details. The proposed gas sensor is featured by high sensitivity, low cost, low loss, miniaturize size, and shows possibility of early detection of leakage.

In the present work, electromagnetic field confinement in a subwavelength waveguide structure is obtained using concepts of quantum mechanics and uncertainty principle. Semi-macroscopic considerations of field interaction at the dielectric interfaces are used in this work. The modal field profile in the subwavelength waveguide is obtained by considering the photon as a particle in the waveguide having finite probability of tunneling. Thus, uncertainty of position is assigned to it. The momentum uncertainty is calculated from position uncertainty. Schrodinger wave equation for the photon is written by incorporating position-momentum uncertainty. The equation is solved and the field distribution in the waveguide is obtained. The field distribution and power confinement is compared with conventional waveguide theory. They were found in good agreement with each other.