Radiation Effects on Long Period Fiber Gratings: A Review

Quasi periodic photonic crystal as gamma detector using Poly nanocomposite and porous silicon

This research investigates the design and performance of quasi-periodic photonic crystals built using Thue-Morse sequences for gamma dosimetry applications. The structures were made of aluminum oxide and porous silicon infused with a poly(ethylene oxide) nanocomposite. The transmittance spectra of these crystals are heavily dependent on their structural evolution, with higher-generation structures exhibiting greater localization of defect modes. The study combines experimental data fitting with theoretical calculations to validate the optical behavior of the developed structures. These calculations were performed using the transfer matrix method over a wavelength range of 500-800 nm. Each structure's sensitivity and quality factor were evaluated in two radiation ranges-0-100 Gy and 100-200 Gy-to determine their potential as gamma dosimeters. The results demonstrate that the proposed structures are highly effective for dosimetry applications. They achieve an optimal balance between sensitivity (0.55 nm/Gy and 0.5 nm/Gy) and sharp defect modes, with quality factors of 1715.9 and 473, respectively. These findings suggest that Thue-Morse sequence-based photonic crystals can serve as highly tunable and efficient gamma radiation sensors.

Topological edge state resonance as gamma dosimeter using poly nanocomposite in symmetrical periodic structure

Topological edge state resonance based sensor, including photonic crystal, is proposed for gamma radiation detection. This article initiates by showing the fundamental principles of photonic crystal, topological edge state, and gamma dosimeter, highlighting their benefits and performance over conventional detectors. This study discusses the possibility of exciting a topological edge state resonance using two symmetrical photonic crystals composed of silicon doped with poly(ethylene oxide) nanocomposite as a gamma detector. The simulation results using the transfer matrix method recorded a sensitivity of 1.24 nm/Gy for gamma doses from 0 to 100 Gy and 0.34 nm/Gy for gamma doses from 100 to 200 Gy when the proposed structure is composed of silicon doped with poly(ethylene oxide) nanocomposite as an active material. It is found that the maximum figure of merit and quality factor of the detector are [Formula: see text] [Formula: see text] and [Formula: see text], respectively. Thus, this innovative topological edge state resonance-based detector is extremely promising for radiation detection. According to these investigations, topological edge state gamma sensors have distinct advantages over traditional dosimeters in terms of increased sensitivity, robustness against disorder, and simplified structure, which makes them appropriate for use in environmental radiation monitoring and medical imaging.

Radiation detector based on coupling between defect mode and topological edge state mode in photonic crystal

Symmetrical one-dimensional photonic crystal structure with polymer nanocomposite materials is introduced as the basis for an extremely sensitive and accurate gamma radiation sensor. The architecture of the sensor makes use of the interaction between a defect mode and a topological edge state to provide remarkable optical performance when exposed to gamma radiation. In response to changing gamma dosages, the transmittance spectra show a noticeable wavelength change and a highly accurate linear correlation. Key performance parameters of the sensor include a sensitivity of 0.2267 nm/RIU and quality factor of 447,747.5. These measurements highlight the sensor's exceptional stability and resolution in detecting even the smallest variations in gamma radiation dosages. With potential uses in industrial, environmental, and medical monitoring, the suggested sensor is a breakthrough in radiation detection. In future work, we aim to enhance sensitivity and utilize more stable materials to improve performance under high radiation doses.

Theoretical study of doped porous silicon in cantor quasi periodic structure for gamma radiation detection

This study looks at two photonic crystals that are similar to Cantor's and are separated by a thin layer of sensitive, porous silicon made of poly(ethylene oxide) nanocomposite and potassium iodide, which is used as a gamma indicator. Modifications in the distinct peak versus the irradiation dose track how the proposed indicator responds to radiation. The results demonstrate that gamma radiation alters the refractive index of the poly(ethylene oxide) nanocomposite, causing the distinct peaks to shift. The impact of doping of nanocomposite with potassium iodide, the porosity of silicon, and the cell's number is analyzed. Doping the sensitive nanocomposite with potassium iodide showed a negative effect. The proposed indicator recorded a high sensitivity of 0.218 nm/Gy (nm/Gy = nanometer/gray) for low gamma doses up to 100 Gy, and a moderated sensitivity of 0.13 nm/Gy for high gamma dose from 100 to 200 Gy. The suggested indicator demonstrated high sensitivity in low gamma detection.

Photonic crystal with a defect layer of silicon containing polymer nanocomposites as radiation detector

This paper presents a photonic crystal-based gamma radiation detector featuring a defect layer of silicon embedded with polymer nanocomposites. The transfer matrix method is utilized as a computational tool to evaluate the transmittance properties of the proposed detector. The study investigates the effects of cell count and porosity on the detector's performance. The model can accurately and simultaneously distinguish between different gamma radiation doses by observing changes in the refractive index of the active layer. The detector demonstrates high sensitivity, with 0.804 nm/Gy for doses ranging from 0 to 100 Gy and 0.225 nm/Gy for doses between 100 and 200 Gy. The proposed model, incorporating porous silicon and ethylene oxide polymer nanocomposites, exhibits exceptional performance as a gamma radiation sensor.

Periodic liquid crystalline waveguiding microstructures

Different methods allowing for creating optical waveguides with liquid-crystal (LC) cores, in which molecules form periodic patterns with precisely controlled periods, are reported. The first one is based on reversible photoalignment with high-resolution selective illumination and allows to control the period of LC molecules inside silica microcapillaries. The second method employs microstructures formed in PDMS, allowing to obtain both: LC-core waveguides and a set of specially designed periodic microelectrodes used for the periodic reorientation of molecules. Using both methods, we successfully controlled the period of the patterned alignment in the range from about 500 µm and scaled it down to as small as 20 µm. We performed experimental studies on waveguiding phenomenon in such structures, in view to obtain transmission spectra typical to optical fiber gratings. Since the results achieved in experimental conditions differed from those expected, the additional numerical simulations were performed to explain the observed effects. Finally, we obtained the waveguiding in a blue phase LC, characterized by naturally created three-dimensional periodicity with periods smaller than one micrometer. In such a structure, we were able to observe first-order bandgap, and moreover, we were able to tune it thermally in nearly the whole visible spectral range.

Innovative Photonic Sensors for Safety and Security, Part III: Environment, Agriculture and Soil Monitoring

In order to complete this set of three companion papers, in this last, we focus our attention on environmental monitoring by taking advantage of photonic technologies. After reporting on some configurations useful for high precision agriculture, we explore the problems connected with soil water content measurement and landslide early warning. Then, we concentrate on a new generation of seismic sensors useful in both terrestrial and under water contests. Finally, we discuss a number of optical fiber sensors for use in radiation environments.

Fiber Optic Sensors for Harsh and High Radiation Environments in Aerospace Applications

In the upcoming space revolutions aiming at the implementation of automated, smart, and self-aware crewless vehicles and reusable spacecraft, sensors play a significant role in the control systems. In particular, fiber optic sensors, with their small footprint and electromagnetic immunity, represent a great opportunity in aerospace. The radiation environment and the harsh conditions in which these sensors will operate represent a challenge for the potential user in the aerospace vehicle design and the fiber optic sensor specialist. We present a review that aims to be a primer in the field of fiber optic sensors in radiation environments for aerospace. We review the main aerospace requirements and their relationship with fiber optics. We also present a brief overview of fiber optics and sensors based on them. Finally, we present different examples of applications in radiation environments for aerospace applications.

Health-Monitoring Systems for Marine Structures: A Review

This paper presents a comprehensive review of the state-of-the-art developments in health monitoring of marine structures. Monitoring the health of marine structures plays a key role in reducing the risk of structural failure. The authors establish the different sensors with their theoretical foundations and applications in order to determine the optimal position of the sensors on board. Once the data were collected, it was necessary to use for subsequent treatment; thus, the authors identified the different methodologies related to the treatment of data collected by the sensors. The authors provide a historical review of the location of different sensors depending on the type of ship and offshore platform. Finally, this review paper states the conclusions and future trends of this technology.

Online Gamma Radiation Monitoring Using Few-Mode Polymer CYTOP Fiber Bragg Gratings

We investigated the gamma radiation response of fiber Bragg gratings (FBGs) inscribed in a few-mode polymer optical fiber. The fiber had a graded-index CYTOP core of 20 µm and XYLEX overclad of 250 µm in diameter. Four FBGs were exposed to gamma radiation during four irradiation sessions at a 5.3 kGy/h dose rate. The FBGs showed a linear Bragg wavelength shift with the received dose with a mean sensitivity of -3.95 pm/kGy at 43 °C. The increased temperature provides a rise in the sensitivity: it reached -10.6 pm/kGy at 58 °C. After irradiation, the FBGs showed partial recovery, which increased with the received dose. Furthermore, the FBG's reflection power decreased with the dose. This attenuation is mainly due to insertion losses caused by the radiation induced attenuation in the CYTOP fiber. Linear response to the received dose makes CYTOP FBGs attractive for gamma radiation dosimetry. However, temperature dependence of the sensitivity should be compensated in practical applications.

Radiation Effects on Fiber Bragg Gratings: Vulnerability and Hardening Studies

Fiber Bragg gratings (FBGs) are point optical fiber sensors that allow the monitoring of a diversity of environmental parameters, e.g., temperature or strain. Several research groups have studied radiation effects on the grating response, as they are implemented in harsh environments: high energy physics, space, and nuclear facilities. We report here the advances made to date in studies regarding the vulnerability and hardening of this sensor under radiation. First, we introduce its principle of operation. Second, the different grating inscription techniques are briefly illustrated as well as the differences among the various types. Then, we focus on the radiation effects induced on different FBGs. Radiation induces a shift in their Bragg wavelengths, which is a property serving to measure environmental parameters. This radiation-induced Bragg wavelength shift (RI-BWS) leads to a measurement error, whose amplitude and kinetics depend on many parameters: inscription conditions, fiber type, pre- or post-treatments, and irradiation conditions (nature, dose, dose rate, and temperature). Indeed, the radiation hardness of an FBG is not directly related to that of the fiber where it has been photo-inscribed by a laser. We review the influence of all these parameters and discuss how it is possible to manufacture FBGs with limited RI-BWS, opening the way to their implementation in radiation-rich environments.

Influence of Optic Cable Construction Parts on Recovery Process after Gamma Irradiation

Fibre optic cables are widely used as communication cables in Instrumentation and Control (I&C) systems. In the case of nuclear power plants (NPPs), using optic cables in mild environments outside of containment areas are very common. However, at present, there is a need for fibre optic cables to be used in containment areas, i.e., with radiation. An optical fibre consists of a highly transparent core that possesses a higher refractive index than the surrounding transparent cladding, which possesses a lower refractive index. Most optical fibres are manufactured from glass (silica with required dopants) which is created at high temperatures from the reaction between gasses. The glass used in optical fibres is sensitive; it becomes dark during exposure to radiation, which compromises the optic functions. That is why there has been a slow infiltration of optic cable in NPP containment areas. Radiation resistant optic fibres have been developed. Although these fibres are called “radiation resistant,” they go through a darkening process (absorbance increase) as well, but not as quickly. Immediately after the irradiation has stopped, a recovery process starts in the glass structure. During this period, optical losses of the glass improve, but not to the original level as before the irradiation. During the testing of optic cables for the installation in nuclear power plant containment areas, we observed an unusual recovery process. In the beginning, a healing effect was observed. However, after a few days of recovery, the healing process stopped, and the trend changed again as a worsening of the optical properties was observed. This paper describes experiments which explain the reasons for such an unexpected behaviour.

Metal-organic Framework Materials Coupled to Optical Fibers for Chemical Sensing: A Review

Metal-organic frameworks (MOFs), a newer class of crystalline nanoporous materials, have been in the limelight owing to their exceptional tunability for structures and physicochemical properties, and have found successful applications in gas storage, gas separation, and catalysis. The mesmerizing properties of MOFs, especially the extensive and tunable porosity and chemical selectivity, also make them an excellent candidate class as chemo-sensory materials. Moreover, MOF-based sensors have attracted considerable attention in the past decade. Recent literature reviews focused on the progress of MOF-based electronic sensors and luminescent MOF sensors, while sensors exploiting the dielectric properties (refractive index) of MOFs were also demonstrated and discussed very recently. The motivation of this report is to provide, for the first time, a general review on such MOF sensors with a particular focus on miniature optical fiber (OF) based MOF sensors and to demonstrate the promising potential of MOFs as dielectric coatings on OF for highly sensitive chemical sensing. The fundamental principle of OF-MOF sensors relies on the tunability of the refractive index of a MOF, which is dependent on the amount and type of adsorbed guest molecules in the MOF pores. MOF sensors based on different optical sensing principles are reviewed; challenges and perspectives on further research into the field of OF-MOF sensors are also discussed.

Arc-Induced Long-Period Fiber Gratings at INESC TEC. Part II: Properties and Applications in Optical Communications and Sensing

In this work, we review the most important achievements of INESC TEC related to the properties and applications of arc-induced long-period fiber gratings. The polarization dependence loss, the spectral behavior at temperatures ranging from cryogenic up to 1200 °C and under exposure to ultraviolet and gamma radiation is described. The dependence of gratings sensitivity on the fabrication parameters is discussed. Several applications in optical communications and sensing domains are referred.

Effect of Low-Doses of Gamma Radiation on Electric Arc-Induced Long Period Fiber Gratings

This work presents an experimental study on the effects of gamma radiation on Long Period Fiber Gratings (LPFGs) in a low-dose test campaign to evaluate their eventual degradation. The study was carried out with standard single-mode fibers where the grating was inscribed using the Electric-Arc Discharge (EAD) technique. Before the gamma campaign, a detailed optical characterization was performed with repeatability tests to verify the accuracy of the setup and the associated error sources. The gamma-induced changes up to a dose of 200 krad and the recovery after radiation were monitored with the Dip Wavelength Shift (DWS). The results show that the gamma sensitivity for a total dose of 200 krad is 11 pm/krad and a total DWS of 2.3 nm has been observed with no linear dependence. Post-radiation study shows that recovery from radiation-induced wavelength shift is nearly complete in about 4000 h. Experimental results show that the changes suffered under gamma irradiation of these LPFGs are temporary making them a good choice as sensors in space applications.

A New Setup for Real-Time Investigations of Optical Fiber Sensors Subjected to Gamma-Rays: Case Study on Long Period Gratings

In this work, we present a new setup for real-time investigations of optical fibers and optical fiber sensors while being subjected to gamma-rays. The investigation of the radiation effects on novel or well-assessed sensing devices has attracted a lot of interest, however, the facilities required to do this (when available) are barely accessible to the device to be characterized. In order to reduce the limitations of these types of experiments and ensure a highly controlled environment, we implemented a configuration that permits the on-line testing of optical components inside a Co-60 gamma chamber research irradiator. To show the advantages of this new approach, we present a case study that compares an arc-induced optical fiber long period grating (LPG) irradiated in a gamma chamber with the same type of grating irradiated with gamma-rays from a Co-60 industrial irradiator. In order to better understand the effects of radiation on such components and their behavior in radiation environments, we focus on the homogeneity of the radiation field and parameter customizability as well as the high reproducibility of the experiments.