Refractive Index Of Liquid Sample Research Articles

Machine Learning Implementation for Unambiguous Refractive Index Measurement Using a Self-Referenced Fiber Refractometer

The implementation of a machine learning algorithm for measuring refractive index of liquid samples using Fresnel reflection at the tip of a fiber is proposed in order to overcome the measurement ambiguity between samples having refractive index values below and above the effective refractive index of the fiber fundamental mode. This is the first time that a machine learning algorithm is implemented in a fiber refractometer. The algorithm, used for pattern classification, is the Support Vector Machine (SVM). The sensing head is formed by two-cascaded cavities that generate an interference pattern that changes each time the fiber is immersed in a different sample. The changes in the interference pattern are classified by the proposed algorithm, which extends the sensing range and eliminates any ambiguity in the obtained RI values. The proposed system is also self-referenced, and therefore it is unaffected by any intensity change of the optical source. A theoretical model and experimental results are presented in detail to demonstrate the effectiveness of the proposed system.

Multipoint fiber optics refractive index sensor based on multimode interference effects.

We demonstrate a fiber optics sensing structure for the measurement of the refractive index of liquid samples at multiple spatial locations simultaneously. The sensing architecture is all-fiber and consists of standard single-mode-multimode-single-mode multimodal interference (MMI) devices working in parallel. The spectral response of each MMI device is carefully engineered to have nonoverlapping responses, such that the entire system can be interrogated with a single broadband light source and single optical spectrum analyzer. In proof-of-concept experiments, we tested the proposed system with aqueous saline solutions and binary solutions of water-glycerol and water-ethylene glycol. Our results validate the use of the proposed platform for the simultaneous monitoring of the refractive index of liquid samples at different locations.

Dual-channel microfluidic sensor based on side-hole fiber with two long-period fiber gratings

We propose and demonstrate a dual-channel microfluidic sensor based on a side-hole fiber (SHF) with two long-period fiber grating (LPFG) structures. There are two air holes in the SHF, which are natural microfluidic channels. We fabricate two LPFGs (long-period gratings LPG-A and LPG-B) in the SHF with the resonance wavelengths of 1268.7 nm and 1385.8 nm, respectively. Results show that the refractive index sensitivities of LPG-A and LPG-B are −76.0 nm/RIU and −71.1 nm/RIU, respectively. One can measure the refractive index of liquid samples in two channels simultaneously. The proposed dual-channel microfluidic sensor has advantages of good linearity response, fluidic technology compatibility, and easy light input/output coupling and system integration, which helps the sensor to have a potential application in environmental detection and food safety detection.

Low-Cost Refractive Index Sensor With Optical Fibers Attached to a U-Shaped Glass Tube

A low-cost multimode optical fiber based sensor has been reported for measuring the refractive index (RI) of liquid samples. In this sensor, a light is coupled from a multimode optical fiber to a customized U-shaped glass tube, and light emerging out of the U-shaped glass tube is guided onto a photodetector with the help of another multimode fiber. The intensity of light detected by the photodetector is found to vary with the RI of liquid sample that comes into contact with the U-shaped glass tube. A sensor response has also been observed by changing the bending radius of the glass tube and the depth of surrounding liquid medium. The proposed sensor is expected to be more rugged and reliable, as compared to a tapered optical fiber and the U-shaped optical fiber refractometers.

Wedge-cell technique as a simple and effective method for chromatic dispersion determination of liquid crystals

In this letter we present a wedge-cell method and then compare it with other techniques that can be used to determinate refractive indices of liquid crystalline materials. This simple goniometric technique is of particular significance when used for liquid crystalline materials characterized by high refractive indices, for which refractometric methods are approaching their upper limits. Importantly, a measurement technique proposed here requires relatively small amount of a liquid crystalline material and gives appropriate results for different light sources from the wide spectral range, allowing thus for chromatic dispersion curves (in different temperatures) to be obtained. Full Text: PDF References M.O. Ko, S. Kim, J. Kim, B.W. Lee, M.Y. Jeon, "Measurement of Effective Refractive Index of Nematic Liquid Crystal in Fabry-Perot Etalon", J. Opt. Soc. Korea 19, 346 (2015). CrossRef K. Thingujama, S. Sarkara, B. Choudhurya, A. Bhattacharjeea, "Effect of Temperature on the Refractive Indices of Liquid Crystals and Validation of a Modified Four-Parameter Model", Acta Phys. Polonica A 122(4), 754 (2012). CrossRef T.A. El-Dessouki, M. Roushdy, N.I. Hendawy, M.M. Naoum, A.A. Zaki, "Optical Measurements of Thermotropic Liquid Crystals", J. Modern Physics 4, 39 (2013). CrossRef J. Li, S. Wu, S. Brugioni, R. Meucci, S. Faetti, "An Experimental Method for Determination of the Refractive Index of Liquid Samples Using Michelson Interferometer" J. Appl. Phys. 97, 073501 (2005). CrossRef B. Abbas, M.A. Khalil, "An Experimental Method for Determination of the Refractive Index of Liquid Samples Using Michelson Interferometer", Acta Phys. Polonica A 129, 59 (2016). CrossRef S.R. Kachiraju, D. A. Gregory, "Determining the refractive index of liquids using a modified Michelson interferometer", Opt. Laser Techn. 44, 2361 (2012). CrossRef J. Yan, M. Jiao, L. Rao, S. Wu, "Direct measurement of electric-field-induced birefringence in a polymer-stabilized blue-phase liquid crystal composite", Opt. Expr. 18, 11450 (2010). CrossRef K.A. Rutkowska, U.A. Laudyn, R.T. Rutkowski, M.A. Karpierz, T.R. Wolinski, J. Wójcik, "Nonlinear light propagation in photonic crystal fibers filled with nematic liquid crystals", Proc. SPIE 6582, 658215 (2007). CrossRef J. Li, C. Wen, S. Gauza, R. Lu, S. Wu, "Refractive indices of liquid crystals for display applications", J. Display Techn. 1, 51 (2005). CrossRef K. Rutkowska, A. Kozak, K. Orzechowski, "Chromatic dispersion measurements of selected liquid crystalline materials for integrated optics applications," Proc. SPIE (in press) (2016). E. Nowinowski-Kruszelnicki, J. Kędzierski, Z. Raszewski, L. Jaroszewicz, R. Dąbrowski, M. Kojdecki, W. Piecek, P. Perkowski, K. Garbat, M. Olifierczuk, "High birefringence liquid crystal mixtures for electro-optical devices", Optica Applicata 42, 167 (2012). DirectLink

SUB-MICRON PLASMONIC WAVEGUIDE FOR EFFICIENT SENSING OF BIO-FLUIDS

A new sensor device is reported to measure the change in dielectric permittivity or refractive index of liquid samples. This novel device is extremely compact in nature and can be fabricated on a chip by integrated optical design method. The device works on change in surface plasmon (SP) amplitude to obtain permittivity values of samples adjacent to a specially designed metal-dielectric interface in a waveguide. The geometry of the interface has a distinct efiect on sensitivity of measurement. The performance of the device is analyzed, and predicted through analytical and numerical calculations.

Fabry-Perot interferometer embedded in a glass chip fabricated by femtosecond laser

We report a simple Fabry-Perot interferometer (FPI) embedded in a glass chip, which is capable of precisely measuring the refractive indices of liquid samples. The microdevice is the integration of a single-mode optical fiber and a microchannel in the photosensitive glass fabricated by femtosecond laser followed by thermal treatment, wet etching, and annealing. The function of the FPI is demonstrated by measuring the refractive indices of water and methanol. The interference visibility is more than 4.0 dB, which is sufficient for most sensing applications. This refractive index sensor with rigid structure could be further integrated to become a more complex 3D lab-on-a-chip for reliable biomedical applications.

Refractive index determination: an application of lensless Fourier digital holography

A simple method for the determination of the refractive index of liquids is demonstrated by using digital holographic interferometry (DHI). A number of experiments are performed to measure the refractive indices of liquid samples. Experimental results reveal that the deviation in refractive index measured by this method and that measured by Abbe refractometer are within experimental limits.

Refractive-index and thickness sensitivity in surface plasmon resonance spectroscopy

The sensitivities of surface plasmon resonance spectroscopy were examined at incident angles of 66-76 deg. The sensitivities were calculated for various refractive indices of liquid samples and for various thicknesses of deposited dielectric thin layers. Furthermore, the sensitivities were confirmed experimentally. The experimentally measured refractive indices and thicknesses were 1.3311-1.3463 and 0-89 nm, respectively. From these results it was demonstrated that the sensing system showed higher sensitivities with smaller incident angles. For example, the sensitivity for a refractive index at a 66 degrees incident angle was seven times larger than that at 76 degrees. It was also demonstrated that the resonant wavelength has a linear relation to the refractive index and the thickness at refractive indices and thicknesses of 1.33-1.345 and 0-100 nm, respectively, except for a 66 degrees incident angle.

Stepwise interferometric method of measuring the refractive index of liquid samples

An iterative interferometric technique for accurately determining the refractive index (RI) of liquid samples is presented. The liquid is measured in an extremely stable stepped cell that is inserted into one arm of a Michelson-type interferometer. The uncertainty of the RI measurement is repeatedly improved by taking successive measurements of the interferometric fringe shifts on adjacent steps in the cell. It is shown that in practice the temperature nonuniformity in the liquid limits the ultimate uncertainty of the RI measurement. The RI resolution of the apparatus described is designed to be 4.3 x 10E-6, and the final RI uncertainty is 1.2 x 10E-5 (2sigma) for a liquid with a RI temperature coefficient of 4 x 10E-4.

Integrated optical interferometer as relative humidity sensor and differential refractometer

Abstract We demonstrate a novel integrated optical interferometer which responds to changes in the relative humidity of gaseous samples and to changes in the refractive index of liquid samples. This common-path interferometer, which can be fabricated without any microstructuring process, consists of a planarmonomode (SiO 2 -TiO 2 ) waveguide in which the TE 0 and TM 0 modes are coherently excited; their time-dependent phase difference caused by the interaction with the sample is measured.