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Editorial Board Members’ Collection Series: Photonics Sensors
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Editorial Board Members’ Collection Series: Photonics Sensors

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Lasers, Light Sources and Sensors".

Deadline for manuscript submissions: 30 June 2024 | Viewed by 22121

Special Issue Editors

Dr. Carlos Marques

E-Mail Website
Guest Editor
CICECO-Aveiro Institute of Materials, Physics Department, University of Aveiro, Aveiro, Portugal
Interests: photonics; optics for aerospace; optical sensors; optical devices; machine learning for optics
Special Issues, Collections and Topics in MDPI journals
Dr. Flavio Esposito

E-Mail Website
Guest Editor
Department of Engineering, University of Naples “Parthenope”, 80143 Naples, Italy
Interests: chemical sensors; biosensors; physical sensors; fiber-optic sensors; fiber gratings; long period gratings; fiber Bragg gratings; fabrication of long period gratings (LPG) in specialty optical fibers; investigation of fiber optic sensors under different ionizing radiations; development of fiber optic bio-chemical sensors for industrial and medical applications
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Photonics sensors have attracted wide interest in countless domains, including aerospace, food processing, high-energy physics experiments, environmental monitoring, medicine, the nuclear industry, oil and gas, railways, and structural health monitoring. Here, photonics sensors bring several advantages, such as high-sensitivity and -resolution measurements, small size and weight, immunity to electromagnetic interferences, resistance to harsh environments, long-distance monitoring, and high multiplexing capability.

This Special Issue will focus on the latest developments and trends in photonics sensors, covering recent improvements in related theory, design, fabrication, and application/validation. We encourage you to submit original research papers, communications, and review articles in order to provide a useful insight into the present status and future outlooks in this area. We look forward to receiving your contributions.

Dr. Carlos Marques
Dr. Flavio Esposito
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • fiber optic sensors
  • interferometric sensors
  • resonance-based sensors
  • plasmonic sensors
  • fluorescence
  • luminescence
  • absorption
  • spectroscopy
  • physical sensors
  • mechanical sensors
  • chemical sensors and biosensors
  • nanostructured materials and coatings
  • surface functionalization procedures
  • microfluidics
  • lab on chip
  • sensor packaging
  • sensor interrogation and instrumentation

Published Papers (17 papers)

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Research

Jump to: Review

23 pages, 2057 KiB  
Article
Specific and Simultaneous Detection of E. coli O157:H7 and Shiga-like Toxins Using a Label-Free Photonic Immunosensor
by Ana Fernández, Manuel Hernández, Yolanda Moreno and Jorge García-Hernández
Photonics 2024, 11(4), 374; https://doi.org/10.3390/photonics11040374 - 16 Apr 2024
Viewed by 457
Abstract
The current study outlines the advancement of an innovative technique for the simultaneous detection of E. coli O157:H7 and its Shiga-like toxins in food samples by utilizing a photonic label-free biosensor coupled with a microfluidic system. This detection method relies on ring resonator [...] Read more.
The current study outlines the advancement of an innovative technique for the simultaneous detection of E. coli O157:H7 and its Shiga-like toxins in food samples by utilizing a photonic label-free biosensor coupled with a microfluidic system. This detection method relies on ring resonator transduction that is functionalized with specific bioreceptors against O157:H7 on silicon nitride surfaces capable of binding specifically to the antigen bacterium and its verotoxins. This experiment included the characterization of selected monoclonal and polyclonal antibodies employed as detection probes through ELISA immunoassays exposed to target bacterial antigens. A thorough validation of photonic immunosensor detection was conducted on inoculated minced beef samples using reference standards for E. coli O157:H7 and its verotoxins (VTx1 and VTx2) and compared to gold-standard quantification. The lowest limit-of-detection values of 10 CFU/mL and 1 ppm were achieved for the detection of bacteria and its verotoxins. In this study, the lowest limit of quantification (LoQ) achieved for bacterial quantification was 100 CFU/mL, and, for verotoxins, it was 2 ppm. This study confirmed the effectiveness of a new quality control and food hygiene method, demonstrating the rapid and sensitive detection of E. coli O157:H7 and its verotoxins. This innovative approach has the potential to be applied in food production environments. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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10 pages, 3439 KiB  
Article
Investigation of Multiple High Quality-Factor Fano Resonances in Asymmetric Nanopillar Arrays for Optical Sensing
by Huawei Chen, Xinye Fan, Wenjing Fang, Shuangshuang Cao, Qinghe Sun, Dandan Wang, Huijuan Niu, Chuanchuan Li, Xin Wei, Chenglin Bai and Santosh Kumar
Photonics 2024, 11(1), 68; https://doi.org/10.3390/photonics11010068 - 08 Jan 2024
Viewed by 966
Abstract
A novel asymmetric all-dielectric metasurface supporting multiple Fano resonances with high quality-factor through the excitation of quasi-bound states in the continuum is theoretically investigated. It is demonstrated that two resonances in the near-infrared wavelength are excited by the symmetry-protected bound state in the [...] Read more.
A novel asymmetric all-dielectric metasurface supporting multiple Fano resonances with high quality-factor through the excitation of quasi-bound states in the continuum is theoretically investigated. It is demonstrated that two resonances in the near-infrared wavelength are excited by the symmetry-protected bound state in the continuum, which can be transformed into the electric dipole and the toroidal dipole quasi-BIC resonance with high quality-factor by breaking the symmetry of metasurface. Moreover, the sensing properties based on different liquid refractive indexes are researched theoretically. The results show that the maximum quality-factor of the Fano resonance peak is 8422, and the sensitivity can reach 402 nm/RIU, with a maximum figure of merit of 2400 RIU−1. This research is believed to further promote the development of optical sensing and nonlinear optics. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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12 pages, 2584 KiB  
Article
The Determination of the Sensitivity of Refractive Index Sensors
by Ilya M. Efimov, Nikolay A. Vanyushkin and Ashot H. Gevorgyan
Photonics 2024, 11(1), 56; https://doi.org/10.3390/photonics11010056 - 04 Jan 2024
Cited by 1 | Viewed by 937
Abstract
A new approach to determining the sensitivity of refractive index sensors is proposed. It has been shown that relative and absolute sensitivity show different results, and also, for the first time, it is demonstrated that relative sensitivity has advantages over absolute sensitivity. In [...] Read more.
A new approach to determining the sensitivity of refractive index sensors is proposed. It has been shown that relative and absolute sensitivity show different results, and also, for the first time, it is demonstrated that relative sensitivity has advantages over absolute sensitivity. In addition, the influence of the relative width of the photonic band gap and the difference in the refractive indices of the layers on the sensitivity are examined and the corresponding dependences of these parameters are obtained. We propose these parameters as a convenient tool for optimizing the sensitivity of sensors based on defective photonic crystals. Finally, results are obtained regarding the behavior of the defect mode at the center of the photonic band gap of one-dimensional photonic crystals. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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14 pages, 3216 KiB  
Article
UV Absorption Spectrum for Dissolved Oxygen Monitoring: A Low-Cost Proposal for Water Quality Monitoring
by Aika Miura, Lorena Parra, Jaime Lloret and Mónica Catalá-Icardo
Photonics 2023, 10(12), 1336; https://doi.org/10.3390/photonics10121336 - 01 Dec 2023
Viewed by 1351
Abstract
One of the key indicators of water quality is dissolved oxygen. Even though oxygen is important in environmental monitoring, the sensors for dissolved oxygen are expensive and require periodic maintenance due to the use of membranes. In this paper, we propose using ultraviolet [...] Read more.
One of the key indicators of water quality is dissolved oxygen. Even though oxygen is important in environmental monitoring, the sensors for dissolved oxygen are expensive and require periodic maintenance due to the use of membranes. In this paper, we propose using ultraviolet light absorption to estimate dissolved oxygen saturation in water samples. The absorption spectrum of dissolved oxygen in the ultraviolet range is investigated over a water matrix with different levels of complexity. First, the difference between different water matrixes is studied. The results indicate similar variations between river water and tap water matrices for comparative purposes. Both samples present much higher absorbance signals than distilled water. Thus, the rest of the tests were performed with only three water matrixes (ultrapure, distilled, and river water). By aerating, water samples were completely saturated. Then, nitrogen gas was used to remove dissolved oxygen from samples to obtain saturations of 75, 50, 25, and 3%. The absorption was measured from 190 to 380 nm, using LLG-uniSPEC 2. The obtained data were used to generate regression models for selected wavelengths (190, 210, 240, and 250 nm). The differences beyond 260 nm for the studied dissolved oxygen saturations were null. The generated models had correlation coefficients from 0.99 to 0.97 for ultrapure water, 0.98 to 0.95 for distilled water, and 0.90 to 0.83 for river water. The maximum differences were found between samples with 75 and 100% of saturation. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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18 pages, 4135 KiB  
Article
Influence of Adhesive Bonding on the Dynamic and Static Strain Transfers of Fibre Optic Sensors
by Chloé Landreau, Adriana Morana, Nicolas Ponthus, Thomas Le Gall, Jacques Charvin, Sylvain Girard and Emmanuel Marin
Photonics 2023, 10(9), 996; https://doi.org/10.3390/photonics10090996 - 31 Aug 2023
Cited by 1 | Viewed by 932
Abstract
The influence of the bonding procedure (the adhesive type, application procedure, etc.) on the static and dynamic strain transfers of bonded optical fibre sensors is studied theoretically and experimentally at room temperature. The achievable performances with four different types of adhesives (three urethane [...] Read more.
The influence of the bonding procedure (the adhesive type, application procedure, etc.) on the static and dynamic strain transfers of bonded optical fibre sensors is studied theoretically and experimentally at room temperature. The achievable performances with four different types of adhesives (three urethane and one epoxy adhesive), and with different fibre types, are evaluated: acrylate-coated, polyimide-coated, and bare single-mode optical fibres. Static strain measurements, ranging from 20 to 200 µ strain, are performed using both fibre Bragg gratings (FBGs) and optical frequency domain reflectometry (OFDR), and are compared to reference strain-gauge measurements, and to the proposed analytical model, which is developed on the basis of stress equilibrium relations. This model is valid for bonding to all types of linear and elastic materials, as long as there is no sliding between the host material, the adhesive, and the optical fibre. The results agree between the analytical model and the experiments. Regarding the dynamic sinusoidal strain measurements, the studied dynamic range is from 10 to 100 Hz, and only the FBGs are tested. The results demonstrate that the sensitivities of strain sensors based on bonded uncoated fibres or bonded polyimide-coated fibres are comparable to those of strain gauges, and that it is possible to use bonded FBGs for precise dynamic strain measurements. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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23 pages, 16196 KiB  
Article
Nonlocal Hydrodynamic Model with Viscosive Damping and Generalized Drude–Lorentz Term
by Milan Burda and Ivan Richter
Photonics 2023, 10(8), 913; https://doi.org/10.3390/photonics10080913 - 09 Aug 2023
Viewed by 713
Abstract
The response of plasmonic metal particles to an electromagnetic wave produces significant features at the nanoscale level. Different properties of the internal composition of a metal, such as its ionic background and the free electron gas, begin to manifest more prominently. As the [...] Read more.
The response of plasmonic metal particles to an electromagnetic wave produces significant features at the nanoscale level. Different properties of the internal composition of a metal, such as its ionic background and the free electron gas, begin to manifest more prominently. As the dimensions of the nanostructures decrease, the classical local theory gradually becomes inadequate. Therefore, Maxwell’s equations need to be supplemented with a relationship determining the dynamics of current density which is the essence of nonlocal plasmonic models. In this field of physics, the standard (linearized) hydrodynamic model (HDM) has been widely adopted with great success, serving as the basis for a variety of simulation methods. However, ongoing efforts are also being made to expand and refine it. Recently, the GNOR (general nonlocal optical response) modification of the HDM has been used, with the intention of incorporating the influence of electron gas diffusion. Clearly, from the classical description of fluid dynamics, a close relationship between viscosive damping and diffusion arises. This offers a relevant motivation for introducing the GNOR modification in an alternative manner. The standard HDM and its existing GNOR modification also do not include the influence of interband electron transitions in the conduction band and other phenomena that are part of many refining modifications of the Drude–Lorentz and other models of metal permittivity. In this article, we present a modified version of GNOR-HDM that incorporates the viscosive damping of the electron gas and a generalized Drude–Lorentz term. In the selected simulations, we also introduce Landau damping, which corrects the magnitude of the standard damping constant of the electron gas based on the size of the nanoparticle. We have chosen a spherical particle as a suitable object for testing and comparing HD models and their modifications because it allows the calculation of precise analytical solutions for the interactions and, simultaneously, it is a relatively easily fabricated nanostructure in practice. Our contribution also includes our own analytical method for solving the HDM interaction of a plane wave with a spherical particle. This method forms the core of calculations of the characteristic quantities, such as the extinction cross-sections and the corresponding components of electric fields and current densities. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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17 pages, 5366 KiB  
Article
FP Interferometric Optic Fiber Humidity Sensor Based on Acrylate AB Adhesive Film
by Qiying Wang, Fangfang Zhang, Mengfan Zhang, Kunpu Zhang, Yaqian Zhang, Guanjun Wang, Zhuhua Hu and Qian Deng
Photonics 2023, 10(8), 873; https://doi.org/10.3390/photonics10080873 - 27 Jul 2023
Cited by 1 | Viewed by 783
Abstract
In this paper, an optical fiber humidity sensor based on acrylate AB adhesive film is studied, and two methods—a bubbling method and a dual pressure assisted method—for preparing thin films are proposed. The forms will make the thin film lighter and make the [...] Read more.
In this paper, an optical fiber humidity sensor based on acrylate AB adhesive film is studied, and two methods—a bubbling method and a dual pressure assisted method—for preparing thin films are proposed. The forms will make the thin film lighter and make the sensor more sensitive. Using a glass tube to connect the acrylate AB adhesive film to the single mode optical fiber, the humidity sensor is obtained. Through humidity response experiments, the sensor’s sensitivity reaches 167.5 pm/% RH, and the response time reaches 4.8 s/% RH. At the same time, the experiments show that the sensor has good repeatability and stability. Finally, the influence of temperature on the working process is analyzed, and we provide a method for improvement through FBG. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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11 pages, 11701 KiB  
Article
Distributed Strain Measurements Based on Rayleigh Scattering in the Presence of Fiber Bragg Gratings in an Optical Fiber
by Valerii Matveenko and Grigorii Serovaev
Photonics 2023, 10(8), 868; https://doi.org/10.3390/photonics10080868 - 26 Jul 2023
Cited by 3 | Viewed by 872
Abstract
This paper addresses the challenge of strain measurement using distributed fiber-optic sensors based on Rayleigh scattering in the presence of fiber Bragg gratings (FBGs) with a reflectivity level of 70% within the optical fiber. The reflectivity of such FBGs complicates distributed strain measurements [...] Read more.
This paper addresses the challenge of strain measurement using distributed fiber-optic sensors based on Rayleigh scattering in the presence of fiber Bragg gratings (FBGs) with a reflectivity level of 70% within the optical fiber. The reflectivity of such FBGs complicates distributed strain measurements that rely on the cross-correlation algorithm. The cases where the scanning ranges of a backscatter reflectometer include the resonant wavelengths of the FBGs and those beyond their limits, resulting in either a complete absence of a useful signal or the emergence of insensitive zones near the FBGs, are considered. An approach is proposed that employs a windowed Fourier transform with Hann window function for signal processing. This method effectively eliminates insensitive zones in distributed strain measurements based on Rayleigh scattering. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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10 pages, 4213 KiB  
Communication
Study on Cortisol Sensing Principle Based on Fluorophore and Aptamer Competitive Assay on Polymer Optical Fiber
by Vivek Semwal, Jonas Højgaard, Emil Møller, Ole Bang and Jakob Janting
Photonics 2023, 10(7), 840; https://doi.org/10.3390/photonics10070840 - 20 Jul 2023
Viewed by 1063
Abstract
In this study, we present a polymer optical fiber fluorophore/aptamer competitive assay-based cortisol sensing principle. We developed a low-cost, two-fiber perpendicular design for fluorophore-based sensing with less input light interference and high output signal intensity. The design is suitable for narrow stokes shift [...] Read more.
In this study, we present a polymer optical fiber fluorophore/aptamer competitive assay-based cortisol sensing principle. We developed a low-cost, two-fiber perpendicular design for fluorophore-based sensing with less input light interference and high output signal intensity. The design is suitable for narrow stokes shift fluorophores. We have demonstrated the cortisol sensing principle based on the competition between tagged and normal cortisol. To date, the sensing design has exhibited a slow response, and we identified possible modifications for improvement. Our estimation shows that with miniaturization and a modified sensor assay compartment design, a less than one-hour response time can be achieved. The reported sensing principle and low-cost new design will be helpful for the future development of fluorophore-based fiber optic aptasensors that can potentially be used in a wet environment for online sensing. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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11 pages, 2736 KiB  
Communication
Immobilized Sorption-Colorimetric Microprobes for Chemical Analysis
by Sergey Kovalev, Tatyana Tikhomirova and Vladimir Apyari
Photonics 2023, 10(7), 787; https://doi.org/10.3390/photonics10070787 - 07 Jul 2023
Viewed by 682
Abstract
Here, we propose a concept of immobilized sorption-colorimetric microprobes for preconcentration and sensing of colored analytical forms. Individual particles of sorbents distributed over a small area of 1 mm × 1 mm and attached to an easy-to-made strip with an adhesive layer were [...] Read more.
Here, we propose a concept of immobilized sorption-colorimetric microprobes for preconcentration and sensing of colored analytical forms. Individual particles of sorbents distributed over a small area of 1 mm × 1 mm and attached to an easy-to-made strip with an adhesive layer were considered as the probes producing colorimetric responses through preconcentration of colored analytical forms. These responses were then directly recorded with a scanner at 1200 dpi, separated from a background, and processed to obtain information about the amounts of analytes. The food dyes Fast Green FCF, and Ponceau-4R were used as the proof-of-concept colored analytes. The microprobes based on silica modified with quaternary ammonium bases and on alumina were studied. Some features of the analytes’ adsorption by the probes and their scanometric sensing were found. It was shown that the proposed method is applicable for the determination of 1–7 mg L−1 of the dyes. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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13 pages, 3420 KiB  
Communication
Optical Sensor Methodology for Measuring Shift, Thickness, Refractive Index and Tilt Angle of Thin Films
by Anton Nalimov, Sergey Stafeev, Victor Kotlyar and Elena Kozlova
Photonics 2023, 10(6), 690; https://doi.org/10.3390/photonics10060690 - 15 Jun 2023
Viewed by 1040
Abstract
We propose a simple optical method and device design for the non-contact determination of small shift, thickness, refractive index, and tilt angle of thin films. The proposed sensor consists of a laser light source, a third- or two-order spiral amplitude zone plate with [...] Read more.
We propose a simple optical method and device design for the non-contact determination of small shift, thickness, refractive index, and tilt angle of thin films. The proposed sensor consists of a laser light source, a third- or two-order spiral amplitude zone plate with a high numerical aperture, and a CCD camera connected to a computer. It is shown that the third-order zone plate transforms the incident Gaussian beam into a three-petal rotating beam. By measuring the rotation angle of the three-petal intensity distribution, one can measure the following: a minimum shift along the optical axis of about 7 nm (the wavelength is 532 nm), a change in the plate thickness by 3 nm, a change in the tilt angle of the plate by 0.1 degrees, and a change in the refractive index by 0.01. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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11 pages, 3869 KiB  
Article
Through-The-Coating Fabrication of Fiber Bragg Grating Relative Humidity Sensors Using Femtosecond Pulse Duration Infrared Lasers and a Phase Mask
by Stephen J. Mihailov, Huimin Ding, Cyril Hnatovsky, Robert B. Walker, Ping Lu and Manny De Silva
Photonics 2023, 10(6), 625; https://doi.org/10.3390/photonics10060625 - 29 May 2023
Cited by 2 | Viewed by 1101
Abstract
Fiber Bragg grating (FBG) relative humidity (RH) sensors are fabricated in commercially available polyimide (PI)-coated optical fibers with diameters of 50 and 125 μm. Infrared (800 nm) femtosecond pulse duration laser pulses and a phase mask are used to inscribe Type-I and Type-II [...] Read more.
Fiber Bragg grating (FBG) relative humidity (RH) sensors are fabricated in commercially available polyimide (PI)-coated optical fibers with diameters of 50 and 125 μm. Infrared (800 nm) femtosecond pulse duration laser pulses and a phase mask are used to inscribe Type-I and Type-II FBGs directly through the protective polyimide coatings of both 50 and 125 μm diameter fibers without typical fiber processing such as hydrogen loading, cryogenic storage, stripping, recoating or annealing. The devices are then evaluated for their performance as humidity sensors. At telecom wavelengths, the 50 μm diameter fiber devices with a 10 μm thick PI coating had a wavelength shift of the Bragg resonance at a constant temperature of 2.7 pm/%RH, whereas the 125 μm diameter fiber devices with a 17 μm thick PI coating had a wavelength shift of 1.8 pm/%RH. The humidity sensors in the 50 µm diameter fiber demonstrated a more rapid response time to small changes in humidity and a weaker hysteresis when compared to the 125 µm diameter fiber devices. No modification to the PI coatings was observed during fabrication. No difference in RH sensitivity was observed for Type-I devices when compared with Type-II devices with the same fiber. The applicability of this approach for fabricating distributed RH sensing arrays with hundreds of sensing elements on a single fiber is discussed. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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12 pages, 2903 KiB  
Article
Remote Operation of an Open-Path, Laser-Based Instrument for Atmospheric CO2 and CH4 Monitoring
by Panagiotis Siozos, Giannis Psyllakis and Michalis Velegrakis
Photonics 2023, 10(4), 386; https://doi.org/10.3390/photonics10040386 - 31 Mar 2023
Cited by 3 | Viewed by 1582
Abstract
The technical specifications and the evaluation of the remote operation of the open-path, tunable diode laser absorption spectroscopic (TDLAS) instrument are presented. The instrument is equipped with two low optical power diode lasers in the near-infrared spectral range for the atmospheric detection of [...] Read more.
The technical specifications and the evaluation of the remote operation of the open-path, tunable diode laser absorption spectroscopic (TDLAS) instrument are presented. The instrument is equipped with two low optical power diode lasers in the near-infrared spectral range for the atmospheric detection of carbon dioxide, methane, and water vapors (CO2, CH4, and H2O). Additionally, the instrument eliminates the requirement of retroreflectors since it detects the back reflection of the laser beam from any topographic target. The instrument was operated remotely by measuring background concentrations of CO2 and CH4 in the atmosphere from 24 November 2022 to 4 January 2023. The accuracy of CO2 and CH4 measurement retrievals on a 200 m laser path was estimated at 20 ppm (4.8%) and 60 ppb (3.1%), respectively. The CH4 accuracy is comparable, but the CO2 accuracy is noticeably lower than the accuracy achieved in local operation. The accuracy issues raised are studied and discussed in terms of the laser driver’s cooling performance. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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12 pages, 8720 KiB  
Article
Silica-Titania Integrated Photonics Platform-Based 1 × 2 Demultiplexer Utilizing Two Serially Cascaded Racetrack Microrings for 1310 nm and 1550 nm Telecommunication Wavelengths
by Muhammad A. Butt, Muhammad Shahbaz, Łukasz Kozłowski, Andrzej Kaźmierczak and Ryszard Piramidowicz
Photonics 2023, 10(2), 208; https://doi.org/10.3390/photonics10020208 - 14 Feb 2023
Cited by 7 | Viewed by 1228
Abstract
Herein, a numerical analysis of a 1 × 2 demultiplexer based on a silica-titania integrated photonics platform is conducted via the finite element method. The structure is composed of two coupled racetrack microrings (RTMRs) and a subwavelength grating (SWG) structure for the demultiplexing [...] Read more.
Herein, a numerical analysis of a 1 × 2 demultiplexer based on a silica-titania integrated photonics platform is conducted via the finite element method. The structure is composed of two coupled racetrack microrings (RTMRs) and a subwavelength grating (SWG) structure for the demultiplexing of 1310 nm and 1550 nm telecommunication wavelengths. The material platform selected for this design is highly attractive due to its refined optical, physical, and chemical properties. Moreover, silica-titania sol-gel thin-films can be deposited on glass substrates with the dip-coating method. The proposed device has a small footprint of 84 × 125 μm2 and offers crosstalk as low as ~−6.6 dB and ~−9.04 dB for 1550 nm and 1310 nm, respectively. We are convinced that this study promotes the use of the silica-titania platform for the development of low-cost on-chip optical communication devices for signal multiplexing and demultiplexing. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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Review

Jump to: Research

24 pages, 2763 KiB  
Review
Advances in Optical Fiber Speckle Sensing: A Comprehensive Review
by Ivan Chapalo, Andreas Stylianou, Patrice Mégret and Antreas Theodosiou
Photonics 2024, 11(4), 299; https://doi.org/10.3390/photonics11040299 - 26 Mar 2024
Viewed by 726
Abstract
Optical fiber sensors have been studied, developed, and already used in the industry for more than 50 years due to their multiplexing capabilities, lightweight design, compact form factors, and electromagnetic field immunity. The scientific community continuously studies new materials, schemes, and architectures aiming [...] Read more.
Optical fiber sensors have been studied, developed, and already used in the industry for more than 50 years due to their multiplexing capabilities, lightweight design, compact form factors, and electromagnetic field immunity. The scientific community continuously studies new materials, schemes, and architectures aiming to improve existing technologies. Navigating through diverse sensor technologies, including interferometry, intensity variation, nonlinear effects, and grating-based sensors, fiber specklegram sensors (FSSs) emerge as promising alternatives due to their simplicity and low cost. This review paper, emphasizing the potential of FSSs, contributes insights to the present state and future prospects for FSSs, providing a holistic view of advancements propelling FSSs to new frontiers of innovation. Subsequent sections explore recent research, technological trends, and emerging applications, contributing to a deeper understanding of the intricacies shaping the future of FFS sensor technologies. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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30 pages, 7939 KiB  
Review
Recent Progress in Photonic Crystal Devices and Their Applications: A Review
by Rahul Kumar Gangwar, Akhilesh Kumar Pathak and Santosh Kumar
Photonics 2023, 10(11), 1199; https://doi.org/10.3390/photonics10111199 - 27 Oct 2023
Cited by 3 | Viewed by 3121
Abstract
The research field of photonic crystals (PhCs) remains active on a global scale. PhCs, which are periodic optical nanostructures with the characteristics of excellent light field confinement and numerous varying degrees of freedom, provide a solid foundation for controlling the movement of light. [...] Read more.
The research field of photonic crystals (PhCs) remains active on a global scale. PhCs, which are periodic optical nanostructures with the characteristics of excellent light field confinement and numerous varying degrees of freedom, provide a solid foundation for controlling the movement of light. Periodic variation of the index of refraction in two or three spatial dimensions with a substantial high-to-low ratio generates a number of intriguing phenomena and enables a variety of potential functionalities. Recently, intriguing devices based on PhCs, such as Y-branches, small-diameter bent waveguides, and miniature resonator cavities, have been proposed and extensively utilized. PhC waveguides are considered ideal candidates for a variety of applications, such as in power splitters, logic gates, sensing and communication fields, etc. These exceptional characteristics may facilitate the development of a dense integrated circuit. However, PhC technology is still relatively new and therefore requires additional effort to fully exploit it. This paper reviews the most popular and essential optical components based on PhCs, including power splitters, modulators, polarization maintaining devices, sensors, and lasers, to summarize the most recent developments relating this hot topic. These devices have superior performance and a smaller footprint compared to conventional photonic devices. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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21 pages, 3839 KiB  
Review
Overview of Addressed Fiber Bragg Structures’ Development
by Timur Agliullin, German Il’In, Artem Kuznetsov, Rinat Misbakhov, Rustam Misbakhov, Gennady Morozov, Oleg Morozov, Ilnur Nureev and Airat Sakhabutdinov
Photonics 2023, 10(2), 175; https://doi.org/10.3390/photonics10020175 - 07 Feb 2023
Cited by 3 | Viewed by 1556
Abstract
An addressed fiber Bragg structure (AFBS) is a special type of fiber Bragg grating simultaneously performing the functions of a two-frequency radiation shaper and a sensitive element. An AFBS forms a two-frequency optical spectral response at its output, the difference frequency of which [...] Read more.
An addressed fiber Bragg structure (AFBS) is a special type of fiber Bragg grating simultaneously performing the functions of a two-frequency radiation shaper and a sensitive element. An AFBS forms a two-frequency optical spectral response at its output, the difference frequency of which is invariant to measured physical fields and is referred to as the address frequency of the AFBS. Each of the AFBSs in the system has its own address frequency; therefore, a number of such structures can be interrogated simultaneously enabling the addressed multiplexing. In this article, we provide an overview of the theory and technology of AFBS, including the structures with three or more spectral components with various combinations of difference frequencies, both symmetrical and asymmetric. The subjects of interrogation of AFBSs, their fabrication and calibration are discussed as well. We also consider a wide range of applications in which AFBS can be used, covering such areas as oil and gas production, power engineering, transport, medicine, etc. In addition, the prospects for the further development of AFBS are proposed that mitigate the shortcomings of the current AFBSs’ state of the art and open up new possibilities of their application. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: An FBG-Based Hard Landing Monitoring System: a preliminary assessment for drops on different grounds
Authors: A. Brindisi; C. Vendittozzi; L. Travascio; M. Belardo; M. Ignarra; V. Fiorillo; A. Concilio
Affiliation: CIRA and the University of Brasilia
Abstract: The activity deals with an integrated system with an FBG-sensor network, capable of recording the structural response of a Landing Gear under operational loads. The focus of the paper concerns the measurements of dynamic strains following hard landing (HL) conditions, even considered for weight on wheel (WoW) detection. Experiments were carried out by dropping a leaf spring LG from a lab tower and impacting different soil types: hard, sand and gravel.

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