The paper presents, and compares the performance of, two optical sensing systems each based on a combination of two fibre Bragg gratings (FBGs) and where a simple measurement of transmitted or reflected power provides an alternative to specialist interrogators. In both configurations one of the FBGs acts as a reference whilst the other is used as the measuring element. It is shown that using FBGs with wide spectra results in higher dynamic range. The measurement of strain is used to demonstrate the behaviour of the proposed sensing systems. The performance of the two systems is compared experimentally and discussed with the insight of the simultaneous measurement of the spectra reaching the detector.

In this work, we propose the use of sensors based on fiber Bragg gratings for identifying the relative position of walls in large facilities and corridors, for example in mines. In smart large facilities such as mines, a backbone network is usually included to automate tasks and maintain safety. By connection of the fiber optic sensor detection network with wireless and radio networks, location information regarding the walls can be sent to the main computer managing the large facility. In this way, safety in large industrial facilities can be improved.

The paper presents the possibility of measuring small distances, and the direction of small positional changes, by using optical sensing systems based on a pair of broadband fibre-optic Bragg gratings. Specifically, the use of Bragg gratings whose spectral profile is asymmetric about the central wavelength is introduced.

Chalcogenide selenide glass fibres have been demonstrated to be well suited for realising lasers operating beyond 5000 nm wavelength with output powers exceeding 100 mW in CW. These devices have many potential commercial applications because they can be in principle tuned over a wide range of wavelengths and can also be potentially made to generate short optical pulses. Therefore in this paper we use a numerical model to study the energy level population dynamics in terbium doped chalcogenide selenide glass fibre under pulsed pumping. The results obtained further the understanding of major dynamic processes governing a mid-infrared pulse generation by a chalcogenide selenide glass host.

A laboratory realization of an actively Q-switched Dy3+-doped fluoride fiber laser operating near 3.0 mu m is reported. Two laser cavities were realized: one based on 1000 ppm Dy3+:ZBLAN fiber and one on 2000 ppm Dy3+:ZBLAN fiber. With the laser cavity based on 1000 ppm Dy3+:ZBLAN fiber a record high peak power of 200 W was achieved with 17 mu J pulse energy and 84.5 ns pulse duration. Moreover, a record short pulse duration of 74 ns was achieved using Q-switched laser cavity composed of 2000 ppm Dy3+:ZBLAN fiber.

In this paper, a highly sensitive water pollutant optical sensor is proposed and analyzed. The suggested sensor consists of photonic crystal fiber with a core surrounded by four elliptical holes infiltrated with the studied analyte (pure/polluted water sample). In addition, two gold nanorods are mounted horizontally at the inner surfaces of two horizontal elliptical holes. The proposed sensor can efficiently detect dissolved pollutants in water such as nitric acid ( HNO_3 ) with concentrations of 14, 23 and 35 H_2O_2 with concentrations of 7, 15 and 30

Nanoplasmonics as enabler of room-temperature quantum nanophotonic networks (Invited), Ortwin Hess Coffee break (11:00 -11:20) Track 1 -Room 2.1 Track 2 -Room 2.2 Track 3 -Room 2.3 Track 4 -Room 3.1 Track 5 -Room 3.2 Track 6

In this work, an efficient optical sensor is proposed for the sensitive detection of various pollutants in water. The suggested optical sensor is based on an indium fluoride (InF 3 ) glass fabricated as a D-shaped optical fiber. The polished surface of the D-shaped fiber is coated with a gold grating to induce the surface plasmon resonance (SPR). The SPR depends on the optical properties of the polluted water analyte in physical contact with the grating. The proposed optical SPR fiber sensor operates within the mid-infrared (MIR) range (3000–4500 nm) to detect any slight change in the water refractive index (RI) due to any pollutants. The full vectorial finite element method (FVFEM) is utilized to calculate the modal properties of the reported sensor. High sensor sensitivity of 17,834 nm/RIU (refractive index units) is achieved for the detection of dissolution of nitric acid (HNO 3 ) in water at a concentration of 14% v/v (volume/volume). Additionally, the reported sensor detects the dissolution of hydrogen peroxide (H 2 O 2 ) in water investigated at concentrations of 15% v/v and 30% v/v, with sensitivities of 12,308 nm/RIU and 17,143 nm/RIU, respectively. Further, suspending polystyrene beads of diameter 0.1 μm in the water at a concentration of 10% v/v gives a maximum sensitivity of 5333 nm/RIU. Therefore, the proposed sensor provides a promising approach for the detection of water pollutants in the MIR wavelength regime, rather than the weaker response in the near infrared.

The paper presents a model sensor system for the simultaneous measurement of fluorescence and transmission for potential application in medical diagnostics. The paper presents results connected with the test substance, fluorescein. The sensor used in the paper includes a neodymium-doped optical fibre to build an asymmetric coupler. The dependence of the intensity of the fluorescence power and transmission on the concentration of fluorescein placed at the end of the system was investigated. Measurements for the presented system were made using UV diode with a wavelength of 415 nm. For the UV source, the effect of fluorescein exposure time on the fluorescence and transmission signals was analysed for different concentrations of fluorescein.

We provide measurements to support our earlier report of continuous wave fiber lasing in a small core Ce3+-doped selenide chalcogenide SIF (step index fiber) of core: Ge-As-Ga-Se chalcogenide glass, doped with 500 ppmw (parts-per-million by weight) of cerium (III). In-band pumping of Ce3+ in fiber, bulk glass and ground glass geometries, at 4.15 mu m wavelength, gives MIR (mid-infrared) photoluminescence spanning 3.40-5.80 mu m wavelength, corresponding to the 2F5/2 <- 2F7/2 electronic emission transition due to Ce3+. Room temperature emission and MIR absorption spectra together enable interpretation of the manifold energies of the first excited state and there is potential for occupied Stark levels in the ground state at room temperature. Both 'tau rad' (PL lifetime) and 'trise' (rise-time through 10% to 90% of maximum PL intensity) are determined: for ground glass at 4.60 mu m wavelength, the best decay fit comprises a primary, and perhaps secondary, lifetime for ground glass of 3.5 ms, and 1.2 ms, and PL rise time of 3.9 ms.

Pulsed fluoride glass fibre based lasers have many potential important applications in materials processing, medicine and defence. At present a number of continuous wave fluoride glass fibre lasers is offered commercially. However, there is still a large scope for the development of pulsed lasers. Therefore, in this contribution we give an up-to-date review of the recent progress in the development of gain switched and Q-switched fluoride glass fibre lasers. Also, we present new experimental results on dysprosium ion doped Q-switched fluoride glass fibre lasers.

The paper describes our investigations of some Fibre Bragg Grating (FBG) systems for measuring basic environmental parameters where a simple measurement of transmitted or reflected power provides an alternative to specialist interrogators. The work targets a low-cost sensor configuration, capable of operating in remote environments and of storing and/or communicating sensing information to a base station.

The paper presents the design, operation, and proof of principle realisation and validation of a relatively cheap fibre optic strain sensor based on two fibre Bragg grating (FBG) elements with different spectral responses. Its performance is compared with the measurement capabilities of a FBG-based sensor that uses an optical interrogator.

We review here our recent work in achieving mid-infrared (MIR) fibre lasing beyond 5 µm wavelength in Ce 3+ -doped selenide-chalcogenide fibre, as well as the observed photoluminescence in samples of the same composition but in particulate and bulk glass form as well as unstructured fibre and in the SIF (step index fibre) in which fibre lasing took place.

In this contribution a comprehensive spectroscopic study of Dy3+ doped fluoroindate glass samples and glass fiber is presented. The mid-infrared (MIR) emission from DyF3 doped bulk glass samples (0.2, 0.4, 0.8, 1.2, 1.4, 1.6 mol.%) is investigated when pumping at 1320 nm. A broadband mid-infrared emission spanning from 2800 nm to 3500 nm with 0.88 ms emission lifetime of the 6H13/2 level in 0.2 mol.% glass sample was observed. Also 0.2 mol.% of DyF3 doped fluoroindate glass fiber was drawn and its photoluminescence properties were studied showing the emission spectrum to 3500 nm and the 6H13/2 level lifetime of 0.91 ms. The results obtained show that fluoroindate glass is a good candidate for further development of tunable fiber lasers and broadband mid-infrared spontaneous emission fiber sources.

We demonstrate how the coupling of a full-wave time-domain boundary element method (BEM) solver with a circuit solver can be used to model 1) the generation of high frequency oscillations in resonant tunneling diode (RTD) oscillators, and 2) the mutual coupling and synchronization of non-identical RTDs with significant differences in frequencies to achieve coherent power combination. Numerical simulations show a combined output power of up to 3.7 times a single oscillator in synchronized devices. The non-differential conductance of the RTD is modeled as a lumped component with a non-linear current-voltage relationship. The lumped element is coupled to the radiating structure using a finite-gap model in a consistent and discretisation independent manner. The resulting circuit equations are solved simultaneously and consistently with time-domain electric field integral equations that model the transient scattering of electromagnetic (EM) fields from conducting surfaces that make up the device. This paper introduces three novel elements: (i) the application of a mesh independent feed line to the modelling of feed lines of RTD devices, (ii) the coupling of the radiating system to a strongly non-linear component with negative differential resistance, and (iii) the verification of this model with circuit models where applicable and against the experimental observation of synchronisation when two RTDs are placed in close proximity. These three elements provide a methodology that create the capacity to model RTD sources and related technology.

The transmission-line modelling (TLM) method has been widely applied to many areas including electromagnetic and heat conduction problems. Its unstructured version, unstructured TLM (UTLM), however, has not hitherto been fully exploited in thermal diffusion problems. This paper derives in detail a thermal UTLM scheme to solve the two-dimensional diffusion equation numerically based on the optimal Delaunay triangular (ODT) mesh.

“ M id- I nfra R ed ( MIR ) fiber photonics” is an important emerging technology worldwide. The MIR spectral region (3 μm wavelength) offers great potential for molecular sensing systems that will translate across sectors from security to healthcare; MIR laser cutting and welding at new wavelengths of soft materials will include medical surgery of human tissue. Chalcogenide glasses present windows within the 1–20 μm region and chalcogenide glass optical fibers are suitable for routing MIR light and as active laser sources. Chapter 8 is a critical review of the last 10 years’ research on lanthanide-ion doped chalcogenide bulk glasses and fibers up to, and including, the advent of bulk glass lasing, at >5 μm, in 2020 and 2021. Photoluminescent behavior is critically analyzed, including absorption and emission cross-sections, lifetimes, branching ratios of praseodymium, dysprosium, terbium and samarium ions doped into a variety of chalcogenide glass hosts. Potential electro-optic traps in chalcogenide glass hosts, as well as optical traps, are discussed for the first time.

Mid-infrared lasers operating near 3 µm are a subject of considerable research effort in recent years. The main reason is the broad range of potential applications for such sources in the field of medicine, environmental monitoring and free space communication. For many applications pulsed mid-infrared light sources with high output energy, short pulse duration (to reduce the impact of thermal background) and good pulse-to-pulse stability are preferred. A promising candidate for such pulsed light sources is a mid-infrared fiber laser realised using fluoride glass fibers doped with rare earth ions (for example erbium or dysprosium). In this contribution pulsed operation was obtained by implementing the Q-switching technique in a laser setup consisting of a fluoride fiber pumped with near infrared laser diodes. The obtained pulses have output energy above 100 µJ, with pulse width below 50 ns and repetition rate in the kilohertz range.

Global and local multitrace formulations (MTFs) provide a flexible and efficient method for the modeling of scattering and transmission of time harmonic electromagnetic (EM) waves by composite structures. This contribution extends the domain of applicability of global MTFs to cases where penetrable domains, perfectly conducting domain, and perfectly conducting thin sheets are all part of the design. A novel and easy to implement resonance-free equation to model scattering by perfect conductors is introduced. A Calderón preconditioner designed to limit the number of iterations required for the solution of the discrete system is designed and studied. The accuracy, flexibility, and efficiency of the method are demonstrated on a representative range of examples.