Sensor For Refractive Index Measurement Research Articles

Nano-Engineered HfO2-Au photonic sensor for ultra-sensitive refractive index detection

In this study, we introduce a novel hafnium dioxide (HfO2) and thin gold layer based photonic crystal fiber (HfAu-PCF) sensor for refractive index measurement and optimize in the spectrum of 1.3 µm to 1.6 µm. The proposed sensor incorporates a D-shaped geometry for enhanced light-matter interaction, and the core of the fiber is surrounded by periodic air holes to facilitate efficient coupling of the guided mode with surface plasmons. The proposed HfAu-PCF sensor is geometrically optimized using finite element method (FEM) by fine-tuning air hole diameter, core size, layer thickness dimensions of the fiber to achieve performance stability. Leveraging the unique optical properties of HfO2 and Au, the sensor demonstrates superior performance metrics, achieving confinement loss (<10−6 dB/m), propagation constant (β) ∼ 6 × 106, V-Parameter < 2.3, a peak relative sensitivity of 99.05 % across the tested wavelength of 1.3 µm to 1.6 µm. Our findings reveal that choosing suitable parameters could lead to further enhancements in sensitivity, making the sensor for applications in bio-sensing, environmental monitoring, and chemical analysis, etc.

Simulation of Trenched Coreless Silica Fiber Sensor for Refractive Index Measurement

Coreless silica fiber has garnered a lot of attention in the field of sensors. Nevertheless, the limitation of conventional and unique coreless silica fiber sensors such as complex simulation, and high fragility of its physical structure needs to be considered. This work presents a simulation of a new coreless silica fiber design in a form of a trenched coreless silica fiber sensor to overcome these limitations. To optimize the sensor’s design, the trench depth was changed in the range of 0 μm to 50 µm at a fixed trench width of 50 μm. The change in analyte refractive index ranging from 1.3000 RIU to 1.4000 RIU was performed to evaluate the simulated sensing performance which showed that the increase in trench depth improved the sensor’s sensitivity with 50 μm being the trench depth at which the highest sensitivity was recorded. Later, the results obtained was compared to the closest in term of design which is the standard coreless fiber. Overall, the trenched coreless silica fiber design provided better sensitivity and is highly capable as of has a new refractive index sensor with an estimated sensitivity of up to 6.62726x10-7, higher than the simulated standard coreless fiber sensor with that of 2.22053x10-7.

Sensitivity enhancement of plasmonic grating in the local field.

A plasmonic grating consisting of parallel gold or silver nanowires on the glass substrate is an excellent sensor for refractive index measurement of a gas or liquid medium. We suggest measuring the local field in a gap between the wires to increase the sensitivity. The local electric field contains more information on the environment since it includes the evanescent waves. Calculation by the boundary element method confirms a substantial improvement of sensitivity owing to a sharp cusp-like gap resonance in the angular dependence. The local field measurement under the frustration of total internal reflection has promising prospects for the development of modern biomedical and chemical sensors.

Highly sensitive refractive index sensor based on degeneracy in specialty optical fibers: a new approach

We study the phenomenon of deliberate inter-modal interactions in a specially designed index guided Microstructured Optical Fiber (MOF) by exploiting multipole expansion method (White et al. 2002). The MOF is designed in such a way that the first layer of holes is judiciously filled with a material having refractive index slightly greater than the background material or core and remaining holes are filled with air. Accordingly, we find an interesting phenomenon of mode crossing between the fundamental mode and a targeted defect mode while tuning the wavelength. Exploring this transition wavelength of the mode crossing, we propose a design of a fiber optic sensor for refractive index measurement (Silva et al. 2014) with enhanced sensitivity.

SPR Microstructured D-Type Optical Fiber Sensor Configuration for Refractive Index Measurement

This paper presents the performance analysis of a sensing configuration of refractive index, based on surface plasmon resonance (SPR) in microstructured D-type optical fiber with a thin gold layer, using the finite-element method. The configuration is analyzed in terms of the loss and distribution Poynting vector. The results are compared with a conventional SPR D-type optical fiber sensor for refractive index measurement. The simulation results show an improvement of the sensitivity and resolution ( $10\times 10^{3}$ nm/RIU and $9.8\times 10^{-6}$ RIU, respectively, when considering an accurately spectral variation detection of 0.1 nm).

Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser micromachining and fusion splicing for refractive index sensing

We demonstrate a fiber in-line Fabry-Perot interferometer cavity sensor for refractive index measurement. The interferometer cavity is formed by drilling a micro-hole at the cleaved fiber end facet, followed by fusion splicing. A micro-channel is inscribed by femtosecond laser micromachining to vertically cross the cavity to allow liquid to flow in. The refractive index sensitivity obtained is ~994 nm/RIU (refractive index unit). Such a device is simple in configuration, easy for fabrication and reliable in operation due to extremely low temperature cross sensitivity of ~4.8 × 10(-6) RIU/°C.

Extrinsic fiber-optic Fabry–Perot interferometer sensor for refractive index measurement of optical glass

A simple fiber-optic sensor based on Fabry-Perot interference for refractive index measurement of optical glass is investigated both theoretically and experimentally. A broadband light source is coupled into an extrinsic fiber Fabry-Perot cavity formed by the surfaces of a sensing fiber end and the measured sample. The interference signals from the cavity are reflected back into the same fiber. The refractive index of the sample can be obtained by measuring the contrast of the interference fringes. The experimental data meet with the theoretical values very well. The proposed technique is a new method for glass refractive index measurement with a simple, solid, and compact structure.

A fibre Bragg grating refractometer

An opto-chemical in-fibre Bragg grating (FBG) sensor for refractiveindex measurement in liquids has been developed using fibre side-polishingtechnology. At a polished site where the fibre cladding has partly beenremoved, a FBG is exposed to a liquid analyte via evanescent field interactionof the guided fibre mode. The Bragg wavelength of the FBG is obtained in termsof its dependence on the refractive index of the analyte. Modal and wavelengthdependences have been investigated both theoretically and experimentally inorder to optimize the structure of the sensor. Using working wavelengths farabove the cut-off wavelength results in an enhancement of the sensitivity of the sensor.Measurements with different mode configurations lead to the separation ofcross sensitivities. Besides this, a second FBG located in the unpolished partcan be used to compensate for temperature effects. Application examplesfor monitoring fuels of varying quality as well as salt concentrations under deepborehole conditions are presented.