Showing papers by "Rajib Chakraborty published in 2016"
TL;DR: In this article, a post-signal processing technique which involves frequency domain weighting was used to increase the operable bandwidth of a fiber Bragg grating-based accelerometer without compromising its sensitivity.
Abstract: We have shown experimentally that the operable bandwidth of a fibre Bragg grating (FBG) based accelerometer can be extended significantly, without compromising its sensitivity, using a post-signal processing technique which involves frequency domain weighting. It has been demonstrated that using the above technique acceleration can be correctly interpreted even when the operating frequency encroaches on the region where the frequency response of the sensor is non-uniform. Two different excitation signals, which we often encounter in structural health monitoring applications, e.g. (i) a signal composed of multi-frequency components and (ii) a sinusoidal excitation with a frequency sweep, have been considered in our experiment. The results obtained have been compared with a piezo accelerometer.
18 citations
TL;DR: In this article, a photonic crystal (PhC)-based structure is designed to achieve sub-diffraction imaging over the entire visible wavelength range, which is a two-dimensional triangular lattice PhC formed by making circular holes in a 100-nm film of electro-optic lithium niobate (LiNbO3).
Abstract: Abstract. A photonic crystal (PhC)-based structure is designed to achieve subdiffraction imaging over the entire visible wavelength range. The designed structure is a two-dimensional triangular lattice PhC formed by making circular holes in a 100-nm film of electro-optic lithium niobate (LiNbO3) grown on indium tin oxide. The analysis is done by using MEEP and MPB softwares. This shows that by applying a voltage within ±460 V, equal frequency contour can be obtained for specific values of frequencies, which corresponds to wavelength (λ) in visible range (389 to 757 nm). This indicates that the designed structure will have effective negative refraction and hence subdiffraction imaging over the entire visible wavelength (frequency) range. By placing this type of PhC structure in front of the objective, the resolution of the conventional imaging system can be increased.
2 citations
TL;DR: It is shown that, when the single dielectric surrounding is replaced by a multilayered surrounding where each layer has different thicknesses and refractive index, the propagation loss gets reduced, leading to increased propagation length of the LR-SPP.
Abstract: A metal waveguide of finite width and thickness surrounded by a dielectric provides increased propagation length of the surface plasmon polariton and is therefore called long-range surface plasmon polaritons (LR-SPP). In this work, a new structure is proposed by modifying the refractive index of the dielectric surrounding the metal waveguide, leading to further improvement of the propagation length. It is shown that, when the single dielectric surrounding is replaced by a multilayered surrounding where each layer has different thicknesses and refractive index, the propagation loss gets reduced, leading to increased propagation length of the LR-SPP. The propagation loss is calculated semianalytically from the FWHM of the Lorentzian peak obtained in the plot of excitation efficiency of such waveguide for different values of the propagation constant. Before doing this calculation, the 2D variation of refractive index is first converted into a 1D effective refractive index. All the steps of analysis are discussed in detail, and, wherever necessary, the calculated results are matched with similar results of other researchers.
1 citations