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A practical realization of a diode pumped actively Q-switched Er3+-doped fluoride fiber laser operating near 2.78 μm is reported. For the repetition rate of 100 Hz stable 26 ns pulses with an energy of 330 μJ and peak power of 12.7 kW are demonstrated. The laser performance is tested against variations in pump power, repetition rate and active fiber length.

Based on tapered Triple-Core Photonic Crystal Fiber (TCPCF), a high performance tunable Dual-Wavelength Erbium-Doped Fiber Laser (DW-EDFL) is proposed and experimentally demonstrated. The mode-coupling among three cores of TCPCF appears periodically and becomes further enhanced in tapered TCPCF, which are beneficial to form a filter to select lasing wavelength. A series of tapered TCPCFs with different taper lengths are fabricated and inserted into tunable DW-EDFL as filters. Multiple groups of tunable dual-wavelength lasing outputs are achieved by using the tapered TCPCF filter with a waist diameter of 126 μm. The maximum tunable range can reach up to 14.36 nm and the side mode suppression ratio of all lasing outputs are above 52 dB. In addition, the tunable single- and triple-wavelength lasers are also obtained. The tunable single-wavelength laser has an excellent linear response to strain and can be applied to realize a high-sensitivity strain sensor with the highest strain sensitivity of -13.1 pm/με.

This Letter, to the best of our knowledge, reports mid-infrared fiber lasing beyond 5 µm at room temperature for the first time, C e 3 + -doped, chalcogenide glass, step index fiber employed in-band pumping with a 4.15 µm quantum cascade laser. The lasing fiber is was 64 mm long, with a calculated numerical aperture of 0.48 at the lasing wavelengths. The core glass was G e 15 A s 21 G a 1 S e 63 atomic % (at. %), doped with 500 parts-per-million-by-weight Ce, with a 9 µm core diameter. The cladding glass was G e 21 S b 10 S e 69 at. % with a 190 µm outer diameter. As pump power increases continuous wave lasing corresponding to the 2 F 7 / 2 → 2 F 5 / 2 , transition in the C e 3 + ion occurs at 5.14 µm, 5.17 µm, and 5.28 µm.

We study numerically a two-dimensional (2-D) elliptical microcavity laser, in the center of which a circular active region is located, modeling a focused pumped spot or an injection electrode. The object of the research is to study lasing spectra, gain-medium thresholds, and modal fields, found as solutions to a classical electromagnetic eigenvalue problem tailored to address the threshold conditions. The instrument of our study is the set of two coupled Muller boundary integral equations (BIE) on the boundaries of the cavity and the active region. These BIEs are discretized by the Nystrom technique that guarantees the convergence. Among the modes that co-exist in such a resonator, we demonstrate the whispering-gallery-like modes (WGM) and the bow-tie-like modes (BTM). We find that the threshold values of material gain of BTMs can become lower than those of nearby WGMs if the radius of the active region in the cavity center is getting sufficiently small.

This paper uses the unstructured transmission line modeling method to investigate near-field interactions between a broadband microwave antenna and a platform that arise as a result of antenna installation. The antenna, feed line, and the platform are represented by a common meshed model and simulated using a single time-domain numerical method. This paper aims to establish guidelines on how to achieve high accuracy when modeling both the near and far fields of an antenna while at the same time prioritizing computational resources. By isolating critical features such as the feed line and selected fine details of the antenna geometry, this paper assesses how accurately these fine features need to be described in the model and how they affect the return loss and far-field pattern of the antenna. The size of the platform is varied from small to medium size (up to 10 wavelengths) and its impact on the antenna performance is assessed. Finally, the conclusions of the study are applied to an example of an antenna installed in the leading edge of an aircraft wing, with and without, a protective radome cover.

In this contribution experimental investigation of acousto-optically Q-switched erbium-doped fluorozirconate fiber laser is presented. Under the repetition rate of 1 kHz laser produces pulses with the shortest duration of 20 ns and the maximum pulse energy of 180 μJ, corresponding to a maximum peak power of 9 kW.

We report a photonic implementation of the Reservoir Computer (PhRC) for sensing application. The kernel of the PhRC will be in the form of chaotic microcavity on a photonic crystal cavity platform designed to discriminate different analytes. The discrimination is achieved by recognising the unique temporal signal signature arising from the chaotic kernel in the presence of different analyte. The unique temporal signature is obtained exploiting the sensitive to the initial-condition response of a billiard shaped microcavity. This is noted that the new discrimination approach reported is performed directly on the temporal signal, in contrast to the conventional spectral fingerprinting.

Mid-infrared (MIR) direct fiber lasers beyond 4 μm wavelength will deliver optimum beam quality of bright, spatially and temporally coherent light, routeable in MIR fiber-optics. They are being developed for applications including narrow-band biomolecular sensing, medical laser surgery at new, long wavelengths and for pulsed seeding of long wavelength MIR-supercontinua in MIR glass fiber for all-fiber, compact systems for broad-band MIR medical sensing and hyperspectral imaging. Low phonon energy, selenide chalcogenide glasses are the optimum glass host for lanthanide ion doping for emission across the 3 to 10 μm wavelength MIR region. Here, we report our recent advances including: >1 mW incoherent emission in the 4-5 μm wavelength region and demonstration of gain beyond 4 μm in Pr3+ doped chalcogenide glass fiber, and proposed quasi three-level lasing beyond 4 μm in Tb3+ doped chalcogenide glass fibers. Encouragingly, since 2020, lasing in both Pr3+ and Tb3+ selenide chalcogenide bulk glasses has been reported. Our overall goal is for new portable, MIR spectroscopic systems based on chalcogenide optical fibers for in vivo sensing, imaging and treatment in healthcare, including for early diagnosis of disease.

Practical realization of gain-switched Dy3+-doped ZBLAN fiber laser operating at 2.94 µm is reported. The laser is pumped by a 1.1 µm Q-switched ytterbium (III) fiber laser, which was constructed in-house. The ZBLAN fiber laser generates a stable pulse train with repetition rates spanning the range from 25 to 100 kHz. At the repetition rate of 50 kHz, the pulse width is 183 ns while energy and peak power are 0.72 µJ and 4 W, respectively.

In this contribution a discussion of design and practical realization of dysprosium ion doped, and erbium ion doped, fluoride glass fiber lasers is given. The specific operating wavelength range that is covered corresponds is near 3000 nm. The discussion is centered around the pulsed Q-switched operation of the fiber laser.

Mid-infrared (MIR) spectroscopy and imaging underpin many applications, ranging from industrial process monitoring to environmental analysis, and offer a new era in healthcare and clinical diagnostics. The spectral region from 1.5 to $12\ \mu \mathrm{m}$ is of interest since it contains strong characteristic absorption peaks associated with the vibrational transitions of many important molecules. A principal requirement for rapid measurement is bright, fibre-based, sources that, if possible, should also be robust and low cost. This paper describes our work to use sources based on the photoluminescence from Pr3+ and Dy3+ doped GeAsGaSe fibres to provide affordable carbon dioxide (CO 2 ) sensing in heritage buildings. Limitations to the Beer Lambert law, previously reported by others, were observed in the sensing system, and the sensors were consequently calibrated empirically. Simulation results show that the use of commercial filters provides a promising approach to realising more compact, real-time, sensing.

A very important problem in modern medicine is the identification of atherosclerotic lesions within human tubular vessels. Current methods such as OCT and intravascular ultrasonography are very expensive and do not provide conclusive information about the formation of atherosclerotic plaques, especially within the human thoracic aorta. This paper presents a new solution to the identification of atherosclerotic lesions based on a specially constructed endoscope that uses CCD cameras. The endoscope analyses the condition of the walls of the blood vessels (side analysis) and represents a step towards an in vivo investigation of part of the human body. The remaining problem is the exact identification of the places where changes occur in the human tubular vessels. Research using the fluorescence phenomenon gives a summary result from an area whose location can be determined with an accuracy of millimetres. For pipes with sufficiently large internal diameter CCD cameras can be used to produce images of the examined tissues. It is possible for doctors to use the images so obtained to identify diseased areas with high accuracy. An alternative approach for identifying atherosclerosis is to use a neural network method to analyse the received pictures. Popular methods such as Machine Learning and Deep Learning can also be used to identify features in medical images. Creating a ‘learning’ database of endoscopic images in which a doctor identifies regions of healthy and atherosclerotic tissue is time consuming. However, after creating the database, the image identification algorithm works much faster than known numerical methods. It can significantly contribute to improving the effectiveness of atherosclerosis diagnostics. This paper presents initial results that confirm the effectiveness of a Machine Learning approach in identifying atherosclerotic lesions from the analysis of endoscope images obtained with a black and white camera following fluorescence stimulation and with a colour CCD camera using white light illumination. These findings are important since histological tests are not possible in in vivo investigations.

Many important molecules show strong characteristic vibrational transitions in the mid-infrared (MIR) part of the electromagnetic spectrum. This leads to applications in spectroscopy, chemical and bio-molecular sensing, security and industry, especially over the mid- and long- wave infrared atmospheric transmission windows of 3-5 μm and 8-13 μm. In this paper, we review some of our more recent experimental and simulation work aimed at developing new light sources based on chalcogenide glass optical fibres that can help us utilize this spectral region for biomedical applications. This includes the development of supercontinuum and bright luminescent sources and our progress towards fibre-based lasers. We place these developments in the context of MIR imaging and spectroscopy in order to show how they bring the promise a new era in healthcare and clinical diagnostics.

Tuneable all-optical signal processing has been the holy grail of information photonics; it has been pursued for many years but has proven to be very challenging. In this contribution, we present our recent work in developing an all-optical signal processing device called a photonic reservoir computer (PhRC) which can be tuned to perform a bespoke task. The PhRC is inspired by how the brain handles and process information. We demonstrate that a chaotic micro-resonator is a suitable platform for the optical implementation of such an artificial neural network.

A dual sakura hollow-core antiresonant fiber (DSHC-ARF) is proposed for developing an ultrawide-bandwidth polarization beam splitter (PBS). An air gap is introduced into the fiber between dual sakura hollow cores acting as a mode-coupling channel, which determines the implementation of a DSHC-ARF-based PBS. We demonstrate the wavelength dependence of coupling length can be reduced by introducing nested tubes and investigate their impact on single-mode operation further. Through optimizing the fiber, a high-performance PBS based on a 4.42 cm long DSHC-ARF can be obtained with an ultrawide bandwidth of 460 nm ranging from 1400 to 1860 nm, good single-mode operation with a higher-order mode extinction ratio above 100, and a low fundamental mode loss below 0.543 dB.

In this paper, a dual-wavelength interval tunable and multi-wavelength switchable fiber laser with high performance is proposed and experimentally demonstrated by using a four-leaf clover suspended core fiber (FLCSCF) filter. The filter, based on mode interference (MI), is fabricated by splicing a 10.5 cm long FLCSCF between two sections of single mode fiber (SMF). The FLCSCF has favorable mode confinement and low transmission loss, which is beneficial for forming a comb-like transmission spectrum with a high extinction ratio. By inserting the MI filter based on FLCSCF into a ring erbium-doped fiber laser (EDFL), switchable single- to six-wavelength lasing outputs are obtained; the optical signal to noise ratio (OSNR) of all lasing outputs is above 50 dB. Dual-wavelength lasing outputs with tunable wavelength intervals are achieved by applying strain on the filter and the maximum tunable range of dual-wavelength lasing outputs can reach up to 41 nm. In addition, six-wavelength lasing outputs exhibit good stability with the wavelength shift less than 0.04 nm and the peak power fluctuation lower than 1.5 dB. Such a multi-wavelength fiber laser (MWFL) with improved performance has great application potential in microwave communications and laser strain sensing.

We propose an As 2 Se 3 -based photonic quasi-crystal fiber (PQF) with high nonlinearity and birefringence. By optimizing the structure parameters, a nonlinear coefficient up to 2079 W −1 km −1 can be achieved at the wavelength of 2 μ m; the birefringence reaches up to the order of 10 −2 due to the introduction of large circular air holes in the cladding. Using an optical pulse with a peak power of 6 kW, a pulse width of 150 f s, and a central wavelength of 2.94 μ m as the pump pulse, a mid-infrared polarized supercontinuum is obtained by using a 15 mm long PQF. The spectral width for x - and y -polarizations covers 1 μ m–10.2 μ m and 1 μ m–12.5 μ m, respectively. The polarization state can be well maintained when the incident angle of the input pulse changes within ±2°. The proposed PQF, with high nonlinear coefficient and birefringence, has potential applications in mid-infrared polarization-maintaining supercontinuum generation.

An electromagnetic wavelength-scale analysis of the optical characteristics of multi-nanolayer photovoltaic (PV) structures: without an antireflection coating, with an antireflection coating on the top of the structure, and with both the antireflection coating on the top and a broadband non-periodic (chirped) distributed Bragg reflector (DBR) on the bottom of the structure is performed. All the PV structures studied are based on a Si p-i-n type absorber supported by a metallic layer (Cu) and SiO2 substrate. The top-to-bottom electromagnetic analysis is performed numerically by the method of single expression (MSE). Absorbing and reflecting characteristics of the multi-nanolayer PV structures are obtained. The influence of the thicknesses and permittivities of the layers of the PV structures on the absorbing characteristics of the structures is analyzed to reveal favourable configurations for enhancement of their absorption efficiency. The localizations of the electric component of the optical field and the power flow distribution within all the PV structures considered are obtained to confirm an enhancement of the absorption efficiency in the favorable configuration. The results of the electromagnetic wavelength-scale analysis undertaken will have scientific and practical importance for optimizing the operation of thin-filmmulti-nanolayer PV structures incorporating a chirped DBR reflector with regards to enhancing their efficiency.

A new method (FTIR continuous dn / dT method, n is refractive index and T temperature) for measuring the continuous thermo-optic coefficients of thin transparent films in the mid-infrared (MIR) spectral region is introduced. The technique is based on Fourier transform infrared (FTIR) transmission spectra measured at different temperatures. It is shown that this method can successfully determine the thermo-optic coefficient of chalcogenide glass thin films (of batch compositions Ge20Sb10Se70 at. % (atomic %) and Ge16As24Se15.5Te44.5 at. %) over the wavelength range from 2 to 25 µm. The measurement precision error is less than ± 11.5 ppm / °C over the wavelength range from 6 to 20 µm. The precision is much better than that provided by the prism minimum deviation method or an improved Swanepoel method.

We demonstrate a maximum gain of 4.6 dB at a signal wavelength of 5.28 μm in a 4.1 μm resonantly pumped Pr3+-doped selenide-based chalcogenide glass fibre amplifier of length 109 mm, as well as a new signal excited-stated absorption (ESA) at signal wavelengths around 5.5 μm. This work to the best of our knowledge is the first experimental demonstration of gain at mid-infrared (MIR) wavelengths in a Pr3+-doped chalcogenide fibre amplifier. The signal ESA of the fibre is attributed to the transition 3H6 → (3F4, 3F3) after the pump ESA (3H5 → 3H6) at a pump wavelength of 4.1 μm, which absorbs the MIR signal at wavelengths of 5.37, 5.51 and 5.57 μm, and so spoils the amplifier’s performance at these wavelengths. Thus, this signal ESA should be suppressed in a resonantly pumped Pr3+-doped selenide-based chalcogenide fibre amplifier.

In this contribution it is shown that broadband emission stretching from 2000 nm up to 6000 nm can be achieved when using selenide-chalcogenide glass. It is also shown experimentally that by appropriate selection of pumping wavelengths the shape of the output spectrum can be varied to suit a particular application.

This paper presents two methods for the segmentation of medical images based on evolutionary algorithms. Such image segmentation is a useful first step in the efficient and speedy analysis of medical images and provides a basis for the next stages of the image analysis process. In particular, the processing of images obtained from the inside of the human body allows for more effective diagnostics of lesions of human tissues. The first approach developed is based on evolutionary algorithms which divide the image into a given number of areas based on the intensity of RGB colours. The second segmentation method is based on the detection of edges in an image. An evolutionary algorithm was also used for this segmentation, based on the search for threshold values in the grey level in the image. We also compare the above segmentation methods with the numerical k-means segmentation method.

M-type fibers have the exceptional property that the higher-order LP0n modes are core-confined and easily excited, while the LP01 and other modes are confined to a high-index ring surrounding the core, so they are not easily excited. This has profound consequences for mid-infrared supercontinuum sources, where the high zero-dispersion wavelength of chalcogenide and ZBLAN fibers means that exotic pump sources have so far been necessary. We show here that in chalcogenide and ZBLAN M-type fibers the lower ZDW of the core-confined higher-order LP02 mode can be in the range of 2 to 3 µm (around 1.55 µm), while the fiber still has a large core diameter and thus supports high average power. This will allow established pump laser technology to be used in future high-power mid-infrared supercontinuum sources.

Due to lattice disorder, glassy semiconductors have energy levels in their bandgaps (gap states) that can be populated by sub-gap illumination or due to recombination of photo-excited carriers. The non-linear optical (NLO) response induced by high-intensity femtosecond (fs) laser pulses develops together with the gap states excitation. These effects in non-crystalline semiconductors have not yet been well studied. In this work, we use two realizations of the pump-probe method [1,2] to study the NLO response of chalcogenide glassy semiconductors of the systems As 40 S x Se 1-x and As 40 Se x Te 1-x with fs resolution in time upon illumination by fs laser pulses with the peak wavelengths λ p of 0.79 and 1.57 μm. By the partial replacement of S by Se in the As 40 S x Se 1-x system and of Se by Te in the As 40 Se x Te 1-x system, the bandgap energy Eg was varied so that the ratio R= hv/E g of the photon energy hv to the bandgap energy Eg was tailored in the range between 0.3 and 0.9. Magnitudes of the NLO coefficients of refraction n 2 and absorption β 2 have been obtained from measurements at each λ p with thin glass samples (thickness ∼1 mm) of each composition. Comparison of the data with the dispersion function G 2 (R) derived in the theory of NLO response of direct-gap crystalline semiconductors [3] (Fig.1a) allowed us to reveal that in the range 0.5 2 for a glass composition decreases with R in a similar way but it is always positive-valued. By solution of kinetic equations for densities of the photo-excited charge carriers, the dielectric constant e was evaluated by using the Drude-Lorentz model. We found that dynamics of the NLO response develop differently with or without a single-photon excitation of gap states [4,5]. In the range 0.3 2 increases with R (Fig.la). Here in the samples with R > 0.38, the two-photon excitation of gap states is possible; this is confirmed by Fig. 1b where the time-resolved NLO response of the samples is compared with the typical trace (inset) obtained in [2] for two-beam coupling signal from fused silica at the wavelength of 1.22 μm (R

Lightning direct effects threats are a major concern for aircraft manufacturers. Of particular concern are fuel ignition threats caused by lightning current transfer between metallic fasteners and surrounding structures leading to voltage arcs, thermal sparks and pressurized gas effects. Although a large percentage of a modern aircraft structure is being replaced by carbon fibre reinforced plastic (CFRP), the main structural components remained joined by means of bolted joints. Although particular choices of fastener technologies are known to affect the current threshold for initiating arcs and sparks, the contributing effects of each design parameter of a structural joint are still not fully understood due to the fact that exploration of these parameters is primarily assessed using measurements. This paper reports a realistic model of a structural joint that includes the metallic bracket (representing a structural spar or rib) joined to the CFRP layer using a detailed model of a fastener (washer, nuts and bolts). The model is simulated using a robust broadband time-domain numerical model based on tetrahedral meshes. The design parameters of the structural joint are explored when high currents are directly injected into the fastener on a metallic bracket.

This work reports on the fabrication and subsequent supercontinuum generation in a Ge-As-Se-Te/Ge-As-Se core/clad chalcogenide step-index fiber with an elliptical-core and an ultra-high numerical aperture of 1.88 ± 0.02 from 2.5 - 15 µm wavelength. The fiber has very low transmission loss of < 2 dB/m from 5-11 µm and a minimum loss of 0.72 ± 0.04 dB/m at 8.56 µm. Supercontinuum spanning from 2.1 µm to 11.5 µm with an average power of ∼6.5 mW was achieved by pumping a ∼16 cm fiber with a minor/major axis core diameter of 4.2/5.2 µm with 250 fs pulses at 4.65 µm wavelength and a repetition rate of 20.88 MHz. The effect of the elliptical-core was investigated by means of mechanical rotation of the fiber relative to the linear pump polarization, and it was found to cause a shift in the supercontinuum spectral edges by several hundred nanometers.

We report on the internal examination of mid-infrared chalcogenide glasses using near-infrared light to reveal light-scattering defects. The technique is demonstrated on imperfectly made chalcogenide glass rods and fiber. This simple, non-destructive technique enables assessment of the interior of glasses and convenient detection of regions containing defects hidden due to the glass opacity to visible light. This method will reveal the presence of unwanted light-scattering defects including nucleated crystals, dust, striae, and bubbles. Hence, this method will help to optimize both chalcogenide glass chemical formulations, against devitrification, and process design to manufacture glass rods and fiber with minimized light scattering defects.

In this contribution the diode pumped high-power Er:ZBLAN laser operating at around 2.8 µm is reported. The laser produces 2 W output power with the slope efficiency of 24 % measured with respect to the incident pump power. Full Text: PDF References S. D. Jackson, "Towards high-power mid-infrared emission from a fibre laser", Nature Photonics 6, 423 (2012). CrossRef V. Portosi, D. Laneve, C. M. Falconi, and F. Prudenzano, "Advances on Photonic Crystal Fiber Sensors and Applications", Sensors 19, (2019). CrossRef M. C. Falconi, D. Laneve, and F. Prudenzano, "Advances in Mid-IR Fiber Lasers: Tellurite, Fluoride and Chalcogenide", Fibers 5, 23 (2017). CrossRef M. Michalska, P. Grześ, J. Świderski, "High power, 100 W-class, thulium-doped all-fiber lasers", Phot. Lett. Poland, 11, 109 (2019). CrossRef Y. O. Aydin, V. Fortin, R. Vallee, and M. Bernier, "Towards power scaling of 2.8 μm fiber lasers", Opt. Lett. 43, 4542 (2018). CrossRef S. Crawford, D. D. Hudson, and S. D. Jackson, "High-Power Broadly Tunable 3- μm Fiber Laser for the Measurement of Optical Fiber Loss", IEEE Photonics Journal 7, 1 (2015). CrossRef V. Fortin, F. Jobin, M. Larose, M. Bernier, and R. Vallee, "10-W-level monolithic dysprosium-doped fiber laser at 3.24 μm", Opt. Lett. 44, 491 (2019). CrossRef L. Sojka, et al., "Experimental Investigation of Mid-Infrared Laser Action From Dy 3+ Doped Fluorozirconate Fiber", IEEE Photon. Technol. Lett. 30, 1083 (2018). CrossRef M. Pollnan and S. D. Jackson, "Erbium 3 /spl mu/m fiber lasers", IEEE J. Sel. Top. in Quantum Electron., 7, 30 (2001). CrossRef Y. O. Aydin, F. Maes, V. Fortin, S. T. Bah, R. Vallee, and M. Bernier, "Endcapping of high-power 3 µm fiber lasers", Opt. Express 27, 20659 (2019). CrossRef C. A. Schafer, "Fluoride-fiber-based side-pump coupler for high-power fiber lasers at 2.8 μm", et al., Opt. Lett. 43, 2340 (2018). CrossRef O. Henderson-Sapir, J. Munch, and D. J. Ottaway, "New energy-transfer upconversion process in Er 3+ :ZBLAN mid-infrared fiber lasers", Opt. Express 24, 6869 (2016). CrossRef F. Maes, V. Fortin, S. Poulain, M. Poulain, J.-Y. Carree, M. Bernier, and R. Vallee, "Room-temperature fiber laser at 3.92 μm", Optica 5, 761 (2018). CrossRef R. I. Woodward, M. R. Majewski, D. D. Hudson, and S. D. Jackson, "Swept-wavelength mid-infrared fiber laser for real-time ammonia gas sensing", APL Photonics 4, 020801 (2019). CrossRef M. Kochanowicz, et al., "Near-IR and mid-IR luminescence and energy transfer in fluoroindate glasses co-doped with Er 3+ /Tm 3+ ", Opt. Mater. Express 9, 4772 (2019). CrossRef M. Kochanowicz, et al., "Sensitization of Ho 3+ - doped fluoroindate glasses for near and mid-infrared emission", Optical Materials 101, 109707 (2020). CrossRef J. Wang, X. Zhu, M. Mollaee, J. Zong, and N. Peyhambarian, "Efficient energy transfer from Er 3+ to Ho 3+ and Dy 3+ in ZBLAN glass", Opt. Express 28, 5189 (2020). CrossRef M. C. Falconi, D. Laneve, V. Portosi, S. Taccheo, and F. Prudenzano, "Design of a Multi-Wavelength Fiber Laser Based on Tm:Er:Yb:Ho Co-Doped Germanate Glass", J Lightwave Technol 1 (2020). CrossRef K. Anders, A. Jusza, P. Komorowski, P. Andrejuk, and R. Piramidowicz, "Short wavelength up-converted emission studies in Er 3+ and Yb 3+ doped ZBLAN glasses", J. Lumin. 201, 427 (2018). CrossRef P. Komorowski ,K. Anders ,U. Zdulska,R. Piramidowicz R. "Erbium doped ZBLAN fiber laser operating in the visible - feasibility study", Photonics Lett Pol 9, 85 (2017). CrossRef J. Swiderski, M. Michalska, and P. Grzes, "Broadband and top-flat mid-infrared supercontinuum generation with 3.52 W time-averaged power in a ZBLAN fiber directly pumped by a 2-µm mode-locked fiber laser and amplifier", Applied Physics B 124, 152 (2018). CrossRef V. Fortin, M. Bernier, S. T. Bah, and R. Vallee, "30 W fluoride glass all-fiber laser at 2.94 μm", Opt. Lett. 40, 2882 (2015). CrossRef

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.

1000 ppmw Sm3+-doped Ge19.4Sb9.7Se67.9Ga3 atomic % chalcogenide bulk glass and unstructured fiber are prepared. Near- and mid-infrared absorption spectra of the bulk glass reveal Sm3+ electronic absorption bands, and extrinsic vibrational absorption bands, due to host impurities. Fiber photoluminescence, centred at 3.75 µm and 7.25 µm, is measured when pumping at either 1300 or 1470 nm. Pumping at 1470 nm enables the photoluminescent lifetime at 7.3 µm to be measured for the first time which was ∼100 µs. This is the longest to date, experimentally observed lifetime in the 6.5-9 µm wavelength-range of a lanthanide-doped chalcogenide glass fiber.

The modeling and design of fiber lasers facilitate the process of their practical realization. Of particular interest during the last few years is the development of lanthanide ion-doped fiber lasers that operate at wavelengths exceeding 2000 nm. There are two main host glass materials considered for this purpose, namely fluoride and chalcogenide glasses. Therefore, this study concerned comparative modeling of fiber lasers operating within the infrared wavelength region beyond 2000 nm. In particular, the convergence properties of selected algorithms, implemented within various software environments, were studied with a specific focus on the central processing unit (CPU) time and calculation residual. Two representative fiber laser cavities were considered: One was based on a chalcogenide&ndash, selenide glass step-index fiber doped with trivalent dysprosium ions, whereas the other was a fluoride step-index fiber doped with trivalent erbium ions. The practical calculation accuracy was also assessed by comparing directly the results obtained from the different models.

A dual hollow-core anti-resonant fiber is proposed and numerically investigated. Two elliptical tubes are introduced to separate the core into two symmetrical cores; further nested tubes are adopted to achieve good single mode performance. Mode coupling takes place in the proposed fiber through an air gap between the two cores; the coupling strength can be controlled by adjusting fiber parameters. A broadband polarization splitter can be constructed by selecting a suitable fiber length. Numerical results show that a polarization splitter based on the proposed fiber has a length of 6.75 cm and a bandwidth of 310 nm, covering the wavelength range from 1.41 μm to 1.72 μm with an extinction ratio as low as −20 dB. The ratio of higher order mode to fundamental mode loss is great than 100, implying that the proposed polarization splitter also possesses effective single mode performance.

In this paper, the Unstructured Transmission Line Modelling (UTLM) method based on a tetrahedral mesh is applied to model the electromagnetic coupling into wire looms and bundles with multiple cores that are typical of an aircraft system, when they are exposed to plane wave illuminations. The impact on the electromagnetic coupling into wires of both bundle configuration and the positioning of the bundle relative to simple structures are investigated using the UTLM method with explicit meshing of the wires. The work not only confirms that UTLM method as a powerful tool for dealing with wire looms and bundles but provides invaluable information on the margins to be expected in key experimental waveform parameters such as peak amplitude and frequency response.

A complex phenomenon including an asymmetric time varying Airy pulse and an asymmetric time varying bounded medium is considered. It is shown that this phenomenon is controlled by a generalised start parameter determined by the point of the source location and the moment of its initiation.

A time-resolved pump-probe method is used for the evaluation of non-linear optical coefficients of chalcogenide glasses from the As-S-Se and Ge-Se systems near their fundamental absorption band edges. The results are analyzed via comparison with the spectral dependencies of the non-linear optical coefficients of crystalline semiconductors; the role of electron transitions through the gap states of chalcogenide glasses is discussed.

In this contribution we use a numerical model to study the photoluminescence emitted by Tb3+ doped chalcogenide-selenide glass fibers pumped by laser light at approximately 3 µm. The model consists of the set of ordinary differential equations (ODEs), which describe the spatial evolution of the pump laser and MIR photoluminescence light within the fiber. The ODEs are coupled with the rate equations that describe the energy level populations. A self-consistent solution of the equation system yields the pump light, MIR photoluminescence and level population distribution within the fiber. Using the developed model we numerically calculate results and discuss the dependence of the output photoluminescence MIR power on the fiber optical loss, fiber length and pump wavelength.

A novel refractive index sensor based on a D-shaped photonic crystal fiber with a nanoscale gold belt is proposed. The nanoscale gold belt is deposited on the flat surface to produce surface plasmon resonance. Numerical results show that the refractive index sensor has a broad measurement range which is from 1.2 to 1.4 and the maximum sensitivity can reach to 3751.5 nm/RIU. The refractive index resolution of the sensor is under 1 × 10−5 RIU in the whole measuring range. A high adjusted R-squared, up to 0.99002, is acquired from the fitting curve of the resonance wavelength. The sensor is sensitive to the variation of the refractive index of analytes and can be applied to the fields of chemical and biological sensing field.

The incorporation of material losses within an unstructured transmission line Modeling electromagnetic field solver is presented. A theoretical and numerical development is complemented by a number of quantified canonical examples. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2218–2222, 2015

In this contribution we present the sensing capabilities of a novel N-path Mach–Zehnder interferometer (MZI) that relies on a multicore microstructured optical fibre (MC-MOF) connected between two sections of standard single mode fibre. The modal properties of the MC-MOF structure are analysed experimentally by measuring near field profiles. The dependence of the N-path MC-MOF MZI sensitivity on temperature, tensile strain and bending is investigated. The results suggest that such an interferometer is a good candidate for a tensile strain or bending sensor.

We present the optical properties such as the linear refractive index ( n ), the absorption coefficient ( α ), the energy band gap ( E g ) and the nonlinear refractive index ( n 2 ) measured by spectroscopy and degenerate four wave mixing methods for Er 3+ -doped oxyfluoride glasses and nano-glass-ceramics. The n 2 of the Er 3+ -doped oxyfluoride nano-glass-ceramic is almost twice that of the Er 3+ -doped parent oxyfluoride glass and undoped oxyfluoride glass. The n 2 values of the Er 3+ -doped oxyfluoride glass and non-Er 3+ -doped oxyfluoride glass are almost the same.

We develop a model of a terbium (111) ion doped selenide chalcogenide glass fibre source that provides spontaneous emission within the mid-infrared (MIR) wavelength range. We use two numerical algorithms to calculate the solution and compare their properties.

The spectral behaviour and the real-time operation of Parity-Time (\(\mathcal {PT}\)) symmetric coupled resonators are investigated. A Boundary Integral Equation (BIE) model is developed to study these structures in the frequency domain. The impact of realistic gain/loss material properties on the operation of the \(\mathcal {PT}\)-symmetric coupled resonators is also investigated using the time-domain Transmission-Line Modelling (TLM) method. The BIE method is also used to study the behaviour of an array of PT-microresonator photonic molecules.

The paper studies the spectral properties of Parity-Time (PT) symmetric photonic structures based on circular microresonators. A semi-analytical model based on solving the Boundary Integral Equation (BIE) is used to model coupled resonators satisfying the PT-symmetric condition. Unique properties such as asymmetric transmission and a localised defect state are observed. A potential benefit of these properties is the generation of a single frequency laser source for spectroscopy or telecommunication applications.

The established time domain Transmission-Line Modelling (TLM) numerical method is extended to include models of (i) saturable dispersive gain and (ii) non-linear dielectric material. The method is used to simulate a photonic memory device based on a nonlinear Parity-Time (PT) structure.

Two time-resolved experimental methods have been used for characterization of the non-linear optical response of chalcogenide glasses of the system As-S-Se-Te in IR and THz ranges upon excitation by femtosecond laser pulses at 800 nm wavelength. Photoinduced conductivity and refractivity were studied by using a rate equation model.

A ray dynamical approach is developed for the study of large-core asymmetric step index fibres (SIF), especially those made from chalcogenide glasses (ChGs) which can exhibit very high refractive index, large numerical aperture, and which are transparent at mid-infrared wavelengths. The model allows for deformations of the SIF away from concentric circular structures, and for the light rays captured by the fibre to behave chaotically within the asymmetric boundaries of the fibre. Chaotic and periodic rays can be classified by the Poincare surface of sections (SOSs). In the model, the ray dynamics in the SIF are approximated by dividing the SOSs into pixels; the construction of a transfer matrix stores all the mapping probabilities. The light intensity distribution in the SOSs is efficiently propagated using the constructed transfer matrix, providing a viable alternative to propagating all the rays in the SIF by brute force ray tracing. The model enables the rapid calculation of the power accumulated in the fibre core following an arbitrary excitation.

The well-known method presented by Swanepoel can be used to determine the refractive index dispersion of thin films in the near-infrared region from wavelength values at maxima and minima, only, of the transmission interference fringes. In order to extend this method into the mid-infrared (MIR) spectral region (our measurements are over the wavelength range from 2 to 25 μm), the method is improved by using a two-term Sellmeier model instead of the Cauchy model as the dispersive equation. Chalcogenide thin films of nominal batch composition As40Se60 (atomic %) and Ge16As24Se15.5Te44.5 (atomic %) are prepared by a hot-pressing technique. The refractive index dispersion of the chalcogenide thin films is determined by the improved method with a standard deviation of less than 0.0027. The accuracy of the method is shown to be better than 0.4% at a wavelength of 3.1 μm by comparison with a benchmark refractive index value obtained from prism measurements on Ge16As24Se15.5Te44.5 material taken from the same batch.