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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All — Fiber Evanescent Wave Sensors for the Mid-Infrared Spectroscopy of Liquids
摘要： Methods of the mid-IR spectroscopy provide reliable tools for detecting chemical composition of gases and liquids. In the mid-IR spectral range (wavelengths of 3-25 μm), various molecules and functional groups have fundamental absorption bands with large absorption coefficients. Creation of materials and technologies for the remote sensors consisting of fiber-optic broadband sources of coherent mid-IR radiation, chalcogenide fibers for transmitting light to the sensing elements and spectrally-selective photodetectors is a problem of a high scientific priority. In this work, we develop the fiber-optic analytical spectroscopy for chemical analysis of aqueous solutions of acetone, ethanol, for determination of the fractional chemical composition of hydrocarbons. As a material base for the fiber-optic sensors, chalcogenide fibers with an extremely low content of impurities have been designed and fabricated by single- and double-crucible methods (including the REE-doped glass fibers). By using these fibers, technologies of fabrication of permanent fiber bends, tapers, microstructured fibers have been developed for using these structures in fiber lasers, supercontinuum generators, sensing elements. A theoretical approach based on electromagnetic theory of optical fibers has been applied for computer-aided design of the evanescent-wave sensors. A sensing element shaped as the U-bent fiber that was applied for chemical analysis of liquid consisting of a diesel oil and a fuel additive is shown. For chemical analysis, the absorption band at the wavelength of 7.83 μm, corresponding to esters, has been chosen. Output characteristics of the sensor were studied in experiment by variation of the fiber core diameter and the bend radius. In a computer model, it was shown that attenuation coefficients of evanescent modes propagating in the fiber bend grow with increase of the bend radius and with decrease of the fiber core diameter. This allows for enhancing sensitivity and decreasing the minimum detectable amount of an analyte. In fact, with an optimised sensing element, the minimum detected amount of the fuel additive was less than 0.1 vol.%.
关键词： evanescent-wave sensors,chalcogenide fibers,chemical analysis,fiber-optic sensors,mid-IR spectroscopy
更新于2025-09-12 10:27:22
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EXPRESS: External Cavity Quantum Cascade Laser-Based Mid-Infrared Dispersion Spectroscopy for Qualitative and Quantitative Analysis of Liquid-Phase Samples
摘要： Acquisition of classical absorption spectra of liquids in the mid-IR range with quantum cascade lasers (QCLs) is often limited in sensitivity by noise from the laser source. Alternatively, measurement of molecular dispersion (i.e., refractive index) spectra poses an experimental approach that is immune to intensity fluctuations and further offers a direct relationship between the recorded signal and the sample concentration. In this work, we present an external cavity quantum cascade laser (EC-QCL) based Mach–Zehnder interferometer setup to determine dispersion spectra of liquid samples. We present two approaches for acquisition of refractive index spectra and compare the qualitative experimental results. Furthermore, the performance for quantitative analysis is evaluated. Finally, multivariate analysis of a spectrally complex mixture comprising three different sugars is performed. The obtained figures of merit by partial least squares (PLS) regression modelling compare well with standard absorption spectroscopy, demonstrating the potential of the introduced dispersion spectroscopic method for quantitative chemical analysis.
关键词： liquid phase,Mid-infrared spectroscopy,QCL,quantum cascade laser,dispersion spectroscopy,mid-IR spectroscopy
更新于2025-09-11 14:15:04
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Ge-Rich Graded-Index SiGe Alloys: Exploring a Versatile Platform for mid-IR Photonics
摘要： In this paper, the recent progress on a new Ge-rich SiGe platform for mid-IR integrated photonics is presented. Low-loss spiral waveguides working over a broadband wavelength range are discussed, followed by a sensing proof-of-concept using a standalone photoresist with a known spectral absorption pattern. In addition, the development of new mid-IR interferometric devices for wavelength filtering and enhancement of the light-matter interaction are presented. Finally, efficient designs to exploit the third-order nonlinearities in these Ge-rich SiGe waveguides at mid-IR wavelengths are shown. The demonstration of these key building blocks will pave the way towards the implementation of new mid-IR photonic integrated systems with multiple functionalities.
关键词： waveguides,non-linear mid-IR photonics,interferometric optical devices,mid-IR integrated photonics,SiGe alloys,mid-IR spectroscopy
更新于2025-09-09 09:28:46