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10 pages, 3262 KiB

Open AccessCommunication

Fluoroindate Glass Co-Doped with Yb³⁺/Ho³⁺ as a 2.85 μm Luminescent Source for MID-IR Sensing

by Marcin Kochanowicz, Jacek Zmojda, Agata Baranowska, Marta Kuwik, Bartłomiej Starzyk, Magdalena Lesniak, Piotr Miluski, Wojciech A. Pisarski, Joanna Pisarska, Jan Dorosz, Maurizio Ferrari and Dominik Dorosz

Sensors 2021, 21(6), 2155; https://doi.org/10.3390/s21062155 - 19 Mar 2021

Cited by 16 | Viewed by 2481

Abstract

This work reports on the fabrication and analysis of near-infrared and mid-infrared luminescence spectra and their decays in fluoroindate glasses co-doped with Yb³⁺/Ho³⁺. The attention has been paid to the analysis of the Yb³⁺→ Ho³⁺ energy [...] Read more.

This work reports on the fabrication and analysis of near-infrared and mid-infrared luminescence spectra and their decays in fluoroindate glasses co-doped with Yb³⁺/Ho³⁺. The attention has been paid to the analysis of the Yb³⁺→ Ho³⁺ energy transfer processed ions in fluoroindate glasses pumped by 976 nm laser diode. The most effective sensitization for 2 μm luminescence has been obtained in glass co-doped with 0.8YbF₃/1.6HoF₃. Further study in the mid-infrared spectral range (2.85 μm) showed that the maximum emission intensity has been obtained in fluoroindate glass co-doped with 0.1YbF₃/1.4HoF₃. The obtained efficiency of Yb³⁺→ Ho³⁺ energy transfer was calculated to be up to 61% (0.8YbF₃/1.6HoF₃), which confirms the possibility of obtaining an efficient glass or glass fiber infrared source for a MID-infrared (MID-IR) sensing application. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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13 pages, 3301 KiB

Open AccessArticle

Luminescence Sensing Method for Degradation Analysis of Bioactive Glass Fibers

by Agata Baranowska, Marcin Kochanowicz, Aleksandra Wajda, Magdalena Leśniak, Jacek M. Żmojda, Piotr Miluski, Izabela Zgłobicka, Krzysztof J. Kurzydłowski and Dominik Dorosz

Sensors 2021, 21(6), 2054; https://doi.org/10.3390/s21062054 - 15 Mar 2021

Cited by 7 | Viewed by 2289

Abstract

The effects of Sm³⁺ content on the optical properties and bioactivity of 13-93 bioactive glass were presented. Sm³⁺ doped glass fibers drawn from bioactive glass were analyzed in simulated body fluid (SBF) for the determination of ion release. Optical analysis of [...] Read more.

The effects of Sm³⁺ content on the optical properties and bioactivity of 13-93 bioactive glass were presented. Sm³⁺ doped glass fibers drawn from bioactive glass were analyzed in simulated body fluid (SBF) for the determination of ion release. Optical analysis of the Sm³⁺ ions in bioactive glass fibers was used for degradation monitoring. While the fibers were immersed in SBF solution, changes in their luminescence spectra under 405 nm laser excitation were measured continuously for 48 h. The morphology of the fibers after the immersion process was determined by SEM/EDS. It was shown that the proposed approach to the analysis of changes in Sm³⁺ ion luminescence is a sensitive method for the monitoring of degradation processes and the formation of hydroxycarbonate-apatite (HCA) layers on glass fiber surfaces. SEM/EDS measurements showed a significant deterioration on the surface of the fibers and the formation of HCA on 13-93_02Sm bioactive glass. The optical analysis of the time constant indicated that bioactive glass fibers doped with 2 %mol Sm³⁺ degrade at a rate almost five times slower than 13-93_02Sm. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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13 pages, 1898 KiB

Open AccessArticle

Design of Tunable Holographic Liquid Crystalline Diffraction Gratings

by Katarzyna A. Rutkowska and Anna Kozanecka-Szmigiel

Sensors 2020, 20(23), 6789; https://doi.org/10.3390/s20236789 - 27 Nov 2020

Cited by 7 | Viewed by 2526

Abstract

Tunable diffraction gratings and phase filters are important functional devices in optical communication and sensing systems. Polarization gratings, in particular, capable of redirecting an incident light beam completely into the first diffraction orders may be successfully fabricated in liquid crystalline cells assembled from [...] Read more.

Tunable diffraction gratings and phase filters are important functional devices in optical communication and sensing systems. Polarization gratings, in particular, capable of redirecting an incident light beam completely into the first diffraction orders may be successfully fabricated in liquid crystalline cells assembled from substrates coated with uniform transparent electrodes and orienting layers that force a specific molecular distribution. In this work, the diffraction properties of liquid crystal (LC) cells characterized by a continually rotating cycloidal director pattern at the cell substrates and in the bulk, are studied theoretically by solving a relevant set of the Euler-Lagrange equations. The electric tunability of the gratings is analyzed by estimating the changes in liquid crystalline molecular distribution and thus in effective birefringence, as a function of external voltage. To the best of our knowledge, such detailed numerical calculations have not been presented so far for liquid crystal polarization gratings showing a cycloidal director pattern. Our theoretical predictions may be easily achieved in experimental conditions when exploiting, for example, photo-orienting material, to induce a permanent LC alignment with high spatial resolution. The proposed design may be for example, used as a tunable passband filter with adjustable bandwidths, thus allowing for potential applications in optical spectroscopy, optical communication networks, remote sensing and beyond. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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11 pages, 2826 KiB

Open AccessArticle

Fluorescence Anisotropy Sensor Comprising a Dual Hollow-Core Antiresonant Fiber Polarization Beam Splitter

by Hanna Izabela Stawska and Maciej Andrzej Popenda

Sensors 2020, 20(11), 3321; https://doi.org/10.3390/s20113321 - 11 Jun 2020

Cited by 13 | Viewed by 3303

Abstract

Fluorescence anisotropy imaging and sensing is a widely recognized method for studying molecular orientation and mobility. However, introducing this technique to in vivo systems is a challenging task, especially when one considers multiphoton excitation methods. Past two decades have brought a possible solution [...] Read more.

Fluorescence anisotropy imaging and sensing is a widely recognized method for studying molecular orientation and mobility. However, introducing this technique to in vivo systems is a challenging task, especially when one considers multiphoton excitation methods. Past two decades have brought a possible solution to this issue in the form of hollow-core antiresonant fibers (HC-ARFs). The continuous development of their fabrication technology has resulted in the appearance of more and more sophisticated structures. One of the most promising concepts concerns dual hollow-core antiresonant fibers (DHC-ARFs), which can be used to split and combine optical signals, effectively working as optical fiber couplers. In this paper, the design of a fluorescence anisotropy sensor based on a DHC-ARF structure is presented. The main purpose of the proposed DHC-ARF is multiphoton-excited fluorescence spectroscopy; however, other applications are also possible. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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20 pages, 14960 KiB

Open AccessArticle

Overhead Transmission Line Sag Estimation Using the Simple Opto-Mechanical System with Fiber Bragg Gratings—Part 2: Interrogation System

by Krzysztof Skorupski, Damian Harasim, Patryk Panas, Sławomir Cięszczyk, Piotr Kisała, Piotr Kacejko, Janusz Mroczka and Michał Wydra

Sensors 2020, 20(9), 2652; https://doi.org/10.3390/s20092652 - 6 May 2020

Cited by 9 | Viewed by 3557

Abstract

This article presents the use of a sensor with fiber Bragg grating along with an interrogation system used for monitoring the overhead lines’ wire elongation. The possible interrogation methods based on adjusted filters were considered. In the experimental part, three types of fiber [...] Read more.

This article presents the use of a sensor with fiber Bragg grating along with an interrogation system used for monitoring the overhead lines’ wire elongation. The possible interrogation methods based on adjusted filters were considered. In the experimental part, three types of fiber Bragg grating pairs, characterized by a small shift in spectra in pairs and gratings with exact matching, were examined. The study showed that, by choosing the appropriate mechanical parameters of the elongation transformer with the optical parameters of the sensor and dedicated filter, the optomechanical system can be adjusted to the required range of overhead line wire sag observation. The range of sag depends on the distance between the poles, the wire type, and its real length in the span, which effectively determines the sag. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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12 pages, 3120 KiB

Open AccessLetter

Reflective Properties of a Polymer Micro-Transducer for an Optical Fiber Refractive Index Sensor

by Paweł Marć, Monika Żuchowska and Leszek R. Jaroszewicz

Sensors 2020, 20(23), 6964; https://doi.org/10.3390/s20236964 - 5 Dec 2020

Cited by 4 | Viewed by 1828

Abstract

A polymer microtip manufactured at the end of a multi-mode optical fiber by using the photopolymerization process offers good reflective properties, therefore, it is applicable as an optical fiber sensor micro-transducer. The reflective properties of this microelement depend on the monomer mixture used, [...] Read more.

A polymer microtip manufactured at the end of a multi-mode optical fiber by using the photopolymerization process offers good reflective properties, therefore, it is applicable as an optical fiber sensor micro-transducer. The reflective properties of this microelement depend on the monomer mixture used, optical fiber type, and light source initiating polymerization. Experimental results have shown that a proper selection of these parameters has allowed the design of a new class of sensing structure which is sensitive to the refractive index (RI) changes of a liquid medium surrounding the microtip. An optical backscatter reflectometer was applied to test a group of micro-transducers. They were manufactured from two monomer mixtures on three different types of multi-mode optical fibers. They were polymerized by means of three optical light sources. Selected micro-transducers with optimal geometries were immersed in reference liquids with a known RI within the range of 1.3–1.7. For a few sensors, the linear dependences of return loss and RI have been found. The highest sensitivity was of around 208 dB/RIU with dynamic 32 dB within the range of 1.35–1.48. Sensing characteristics have minima close to RI of a polymer microelement, therefore, changing its RI can give the possibility to tune sensing properties of this type of sensor. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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13 pages, 3707 KiB

Open AccessLetter

Numerical and Experimental Analysis of Matched Filter Interrogation of FBG Sensors with Large Side Lobes

by Krzysztof Skorupski, Sławomir Cięszczyk, Patryk Panas and Piotr Kisała

Sensors 2020, 20(19), 5522; https://doi.org/10.3390/s20195522 - 27 Sep 2020

Cited by 1 | Viewed by 2806

Abstract

This article presents the effect of fiber Bragg gratings side lobes on interrogation systems consisting of sensor and matched filters. The conducted research shows that high-value side lobe structures applied as sensors and/or filters are characterized by some interesting properties. The paper presents [...] Read more.

This article presents the effect of fiber Bragg gratings side lobes on interrogation systems consisting of sensor and matched filters. The conducted research shows that high-value side lobe structures applied as sensors and/or filters are characterized by some interesting properties. The paper presents both numerical analysis and experimental verification of the fiber Bragg gratings (FBG) interrogation systems with matched filters for gratings containing high side lobes. Numerical modeling of Bragg structures was performed for two different cases: uniform and inverse apodization. Modification of apodization can change the side lobe reflectance level even above levels found in uniform structures. This is a case not described in the literature, especially in terms of possible applications. Transfer characteristics, i.e., the relationship between power intensity as a function of wavelength shift, were determined. A collection of gratings with spectra corresponding to those analyzed in numerical experiments were fabricated. Next, the transfer characteristics of the interrogation systems containing real FBG were determined. The properties of the proposed systems are described. It has been shown that a significant level of sidebands, which is often the subject of many drawbacks in filtering or telecommunications systems, can be an advantage. It has been demonstrated that a high level of side lobes can be used to increase the measurement range of the FBG sensor interrogation systems. It has been determined numerically and confirmed experimentally that from the point of view of the design of sensor interrogation systems, it is beneficial to combine specific pairs of gratings: one with a spectrum characterized by a low side lobe level and a second one in which the spectrum has very high side lobes. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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10 pages, 4262 KiB

Open AccessLetter

UV Sensor Based on Fiber Bragg Grating Covered with Graphene Oxide Embedded in Composite Materials

by Piotr Lesiak, Karolina Bednarska, Krzysztof Małkowski, Łukasz Kozłowski, Anna Wróblewska, Piotr Sobotka, Kamil Dydek, Anna Boczkowska, Tomasz Osuch, Alicja Anuszkiewicz, Wojciech Lewoczko-Adamczyk, Henning Schröder and Tomasz Ryszard Woliński

Sensors 2020, 20(19), 5468; https://doi.org/10.3390/s20195468 - 24 Sep 2020

Cited by 2 | Viewed by 2715

Abstract

Polymer–matrix composites degrade under the influence of UV radiation in the range of the 290–400 nm band. The degradation of polymer–matrix composites exposed to UV radiation is characterized by extensive aging of the epoxy matrix, resulting in deterioration of their mechanical properties. Glass [...] Read more.

Polymer–matrix composites degrade under the influence of UV radiation in the range of the 290–400 nm band. The degradation of polymer–matrix composites exposed to UV radiation is characterized by extensive aging of the epoxy matrix, resulting in deterioration of their mechanical properties. Glass fibers/epoxy resin composites were made by an out-of-autoclave method whereas a fiber optic sensor was placed between different layers of laminates. In our work, we used a fiber Bragg grating sensor covered with graphene oxide and embedded in a polymer matrix composite to monitor UV radiation intensity. Measurements of UV radiation may allow monitoring the aging process of individual components of the polymer composite. In order to estimate the number of microcracks of epoxy resin, microstructure observations were carried out using a scanning electron microscope. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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11 pages, 3497 KiB

Open AccessLetter

Experimental Investigation of Actively Q-Switched Er³⁺:ZBLAN Fiber Laser Operating at around 2.8 µm

by Lukasz Sojka, Lukasz Pajewski, Samir Lamrini, Mark Farries, Trevor M. Benson, Angela B. Seddon and Slawomir Sujecki

Sensors 2020, 20(16), 4642; https://doi.org/10.3390/s20164642 - 18 Aug 2020

Cited by 15 | Viewed by 3808

Abstract

A diode-pumped Q-switched Er³⁺:ZBLAN double-clad, single-transverse mode fiber laser is practically realized. The Q-switched laser characteristics as a function of pump power, repetition rate, and fiber length are experimentally investigated. The results obtained show that the Q-switched operation with 46 µJ [...] Read more.

A diode-pumped Q-switched Er³⁺:ZBLAN double-clad, single-transverse mode fiber laser is practically realized. The Q-switched laser characteristics as a function of pump power, repetition rate, and fiber length are experimentally investigated. The results obtained show that the Q-switched operation with 46 µJ pulse energy, 56 ns long pulses, and 0.821 kW peak power is achieved at a pulse repetition rate of 10 kHz. To the best of our knowledge, this is the highest-ever demonstrated peak power emitted from an actively Q-switched, single-transverse mode Er³⁺:ZBLAN fiber laser operating near 2.8 µm. Full article

(This article belongs to the Special Issue Selected Papers from the 19th Conference on Optical Fibers and Their Applications (OFTA 2020))

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