Multi-material Optical Fibers Research Articles

Generation of stabilized electrically-induced micro-plasma at the tip of multimaterial optical fibers

The aim of this work is to optimize the operation of a multimaterial optical fiber device to generate a stabilized electrically-induced micro-plasma. The fiber is composed of a polymer cladding with a central hole surrounded by two cylindrical metal electrodes. When a DC voltage of 1.2 kV is applied between electrodes, an air micro-plasma is generated at the tip of the fiber. In order to stabilize the discharge, studies are focused on the modification of the electrical properties of the fiber tip by covering the electrodes with resistive layers. A comparison between two different layers (semi-conductive and semi-insulating) is shown. Characterizations were also performed for the fiber (head and length), and the plasma (imaging, spatial and temporal stability). The results show the effectiveness of the method to cover at least one of the electrodes by the semi-insulating layer to generate a permanent and stable discharge. In fact, this method allowed to increase considerably the lifetime of our technology and avoid the electric arcs leading to high instabilities. According to the Optical Emission Spectroscopy (OES), the species generated by the fiber-plasma device were identified.The combination of the characteristics of optical fibers with the properties of plasma allows diverse potential applications, such as gas detection in remote, confined, or harsh environments, high-level disinfection and sterilization of medical equipment or high-quality surface treatment (micrometric scale).

Soft, stretchable optical fibers via thermal drawing

Optical fibers that can sustain large elastic deformations are promising building blocks in soft robotics, medical and wearable devices, and advanced textiles. Thus far, however, the fabrication methods developed for soft optical fibers have remained unmatured. Here, we present thermal drawing as a materials and processing platform to fabricate 10s of meters-long soft, multi-material optical fibers with intriguing architectures. It offers unprecedented opportunities to realize step-index soft optical fibers, as well as photonic crystal fibers for transmission, reflection, and sensing.

Evolutive Optical Fibers Combining Oxide and Chalcogenide Glasses with Submicronic Polymer Structures

Multimaterial optical fibers combining tellurite with chalcogenide glasses and featuring thin polymer structures are fabricated via the thermal drawing process. It is demonstrated that micrometric polyethersulfone films can be embedded within larger elongated tellurite/chalcogenide glass architectures. Taking advantage of the strong chemical reactivity contrasts which exist in the considered fiber geometries, a quasi‐exposed‐core waveguide is obtained by selective etching of the glass cladding. The potential of the postprocessed fiber structure is then assessed through evanescent‐wave probing of liquids and numerical investigations are carried out to establish the device performances as function of selected optogeometric parameters. Those results open the way for the development of evolutive photonic objects benefiting from postdrawing processing of multimaterial fibers.

Semiconductor Multimaterial Optical Fibers for Biomedical Applications.

Integrated sensors and transmitters of a wide variety of human physiological indicators have recently emerged in the form of multimaterial optical fibers. The methods utilized in the manufacture of optical fibers facilitate the use of a wide range of functional elements in microscale optical fibers with an extensive variety of structures. This article presents an overview and review of semiconductor multimaterial optical fibers, their fabrication and postprocessing techniques, different geometries, and integration in devices that can be further utilized in biomedical applications. Semiconductor optical fiber sensors and fiber lasers for body temperature regulation, in vivo detection, volatile organic compound detection, and medical surgery will be discussed.

Development of a Multimaterial Optical Fiber for Fully Distributed Magnetic Sensing Applications

A novel multimaterial fiber optic magnetic sensing design is presented and evaluated in this letter. The multimaterial optical fiber has demonstrated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ &lt; 0.2\ n\epsilon $</tex-math></inline-formula> sensitivity to external magnetic fields over a 2-m gauge length. Intended for immediate use in unconventional oil and gas (UOG) and measuring while drilling (MWD), this instrument could have wide-ranging subsurface sensing applications. Composed of fused silica cladding, internally distributed ferromagnetic nickel, and a series of fiber Bragg gratings, the multimaterial structure has been consistently drawn to over 1 km of length on a fiber draw tower. Due to the consistency of manufacturability and high magnetic sensitivities over long lengths, the proposed design may be considered a competitive magnetic sensor in UOG and MWD applications.

Multifunctional single‐crystal tellurium core multimaterial fiber via thermal drawing and laser recrystallization

AbstractIn the field of multimaterial optical fibers, the demand for high‐performance single‐crystal core glass‐clad multimaterial optical fibers is increasing. However, the applications of single‐crystal fibers are restricted by the complex fabrication processes and the slow growth of single‐crystal materials. Here, a two‐step method is demonstrated to achieve single‐crystal tellurium (Te) core fibers with high crystal quality over the length of the fiber. This method starts with the thermal drawing of a fiber preform into polycrystalline Te core multimaterial fibers (precursor fibers) that are long and mechanically stable. A 532‐nm continuous laser is then employed to recrystallize the Te core in the precursor fiber into a single crystal state along the entire length of the fiber. Experimental studies of these single‐crystal fibers demonstrate that the single‐crystal Te core fibers possess high transmittance (&gt;90% at 2–10 μm) and high thermoelectric performance (ZT values from 0.03 to 0.13 at 300 K temperature). They are superior to previous reports and our previous work. This method works for fabricating various single‐crystal fibers and has important applications in the field of optical fibers, functional fibers, and their integrated devices.

All-polymer multimaterial optical fiber fabrication for high temperature applications

In this work, we report the fabrication of an all-polymer multimaterial optical fiber based on two different grades of cyclo-olefin polymers (known as Zeonex) and the high-performance thermoplastic polysulfone (PSU) with glass transition temperature (Tg) of 189&#x00B0;C. The core/cladding structure using the Zeonex polymers (E48R/480R, respectively) was developed using a co-extrusion method followed by a rod-in-tube approach to form the final preform. The fiber materials were characterized in terms of their Tg, viscosity as well as refractive index profiles. The final preform was thermally drawn down to a fiber with &#x223C;300 &#x00B5;m and &#x223C;70 &#x00B5;m total and core diameter, respectively. We thermally characterized and compared our step-index fiber with a commercially available polymer (Cytop) as well as a purely Zeonex single-mode step-index fiber. The proposed multimaterial fiber exhibited stable operation at temperatures as high as 180&#x00B0;C being &#x223C;35&#x00B0;C higher than any polymer fiber reported so far to the best of our knowledge. Therefore, we believe that our results constitute a significant step forward for the polymer optical fiber community making the proposed polymer multimaterial fiber an efficient route towards truly heat-resistant applications.

3D-printing of arsenic sulfide chalcogenide glasses

The use of a 3D-printing additive manufacturing process is reported for the first time for the extrusion of chalcogenide glasses by using a filament feed. Several challenges were overcome: preparation of chalcogenide glass filaments by the crucible technique, optimization of extrusion temperature or even filament feeding. The As40S60 chalcogenide glass was selected for its low glass transition temperature (Tg = 188°C) and ease of synthesis and processing. It was extruded using a commercial 3D-printer at a temperature around 140°C above the glass transition temperature. 3D-printed glass specimens were then characterized and no significant difference was observed in comparison with the bulk precursor glass in terms of chemical and thermal properties. This first report of additive manufacturing of chalcogenide glass complex shapes paves the way for the development of novel specialty optical components that could not be produced by conventional methods, including the fabrication of multimaterial optical fiber preforms.

Superelastic Multimaterial Electronic and Photonic Fibers and Devices via Thermal Drawing.

Electronic and photonic fiber devices that can sustain large elastic deformation are becoming key components in a variety of fields ranging from healthcare to robotics and wearable devices. The fabrication of highly elastic and functional fibers remains however challenging, which is limiting their technological developments. Simple and scalable fiber-processing techniques to continuously codraw different materials within a polymeric structure constitute an ideal platform to realize functional fibers and devices. Despite decades of research however, elastomeric materials with the proper rheological attributes for multimaterial fiber processing cannot be identified. Here, the thermal drawing of hundreds-of-meters long multimaterial optical and electronic fibers and devices that can sustain up to 500% elastic deformation is demonstrated. From a rheological and microstructure analysis, thermoplastic elastomers that can be thermally drawn at high viscosities (above 103 Pa s), allowing the encapsulation of a variety of microstructured, soft, and rigid materials are identified. Using this scalable approach, fiber devices combining high performance, extreme elasticity, and unprecedented functionalities, allowing novel applications in smart textiles, robotics, or medical implants, are demonstrated.

Feature issue introduction: Multimaterial and Multifunctional Optical Fibers

The development of multimaterial and multifunctional optical fibers is opening exciting opportunities in photonic and optoelectronic devices, optical probes, diagnosis and surgical tools, as well as advanced fibers and textiles. It also constitutes a rich platform for the fundamental study of novel materials science and processing concepts, as well as in optics and photonics. This Feature Issue is a collection of thirteen peer-reviewed articles that present original work in areas at the frontier of this emerging scientific and technological field. These contributions highlight the maturity of the techniques employed to date, their potential to further develop and the prospects for a new generation of optical fiber based devices. (C) 2017 Optical Society of America

Sol–gel silica glass-cladding semiconductor-core optical fiber

Hybrid optical fibers consisting of glass clad and semiconductor core materials are extensively investigated due to their interesting properties that make them attractive for several technological applications. Here, we report on a new approach for the fabrication of such multi-material optical fiber preform using the sol–gel technique. It consists in mechanically drilling a central hole in a silica xerogel rod, then in filling this hole with a centimeter-length silicon rod, and finally in densifying the silica glass jacket around the silicon core. By drawing this preform, a homogenous hybrid rod-type fiber was obtained. The composition and the structural properties of the pristine silicon rod, of the hybrid preform and of the drawn fiber have been investigated using electron probe microanalysis, Raman spectroscopy and transmission electron microscopy. We have shown that the silicon core material preserves its composition and polycrystalline structure all along the fabrication process.

Multiplexed neural recording along a single optical fiber via optical reflectometry.

.We introduce the design and theoretical analysis of a fiber-optic architecture for neural recording without contrast agents, which transduces neural electrical signals into a multiplexed optical readout. Our sensor design is inspired by electro-optic modulators, which modulate the refractive index of a waveguide by applying a voltage across an electro-optic core material. We estimate that this design would allow recording of the activities of individual neurons located at points along a 10-cm length of optical fiber with axial resolution and sensitivity down to using commercially available optical reflectometers as readout devices. Neural recording sites detect a potential difference against a reference and apply this potential to a capacitor. The waveguide serves as one of the plates of the capacitor, so charge accumulation across the capacitor results in an optical effect. A key concept of the design is that the sensitivity can be improved by increasing the capacitance. To maximize the capacitance, we utilize a microscopic layer of material with high relative permittivity. If suitable materials can be found—possessing high capacitance per unit area as well as favorable properties with respect to toxicity, optical attenuation, ohmic junctions, and surface capacitance—then such sensing fibers could, in principle, be scaled down to few-micron cross-sections for minimally invasive neural interfacing. We study these material requirements and propose potential material choices. Custom-designed multimaterial optical fibers, probed using a reflectometric readout, may, therefore, provide a powerful platform for neural sensing.

X-ray tomography for structural analysis of microstructured and multimaterial optical fibers and preforms.

Specialty optical fibers, in particular microstructured and multi-material optical fibers, have complex geometry in terms of structure and/or material composition. Their fabrication, although rapidly developing, is still at a very early stage of development compared with conventional optical fibers. Structural characterization of these fibers during every step of their multi-stage fabrication process is paramount to optimize the fiber-drawing process. The complexity of these fibers restricts the use of conventional refractometry and microscopy techniques to determine their structural and material composition. Here we present, to the best of our knowledge, the first nondestructive structural and material investigation of specialty optical fibers using X-ray computed tomography (CT) methods, not achievable using other techniques. Recent advances in X-ray CT techniques allow the examination of optical fibers and their preforms with sub-micron resolution while preserving the specimen for onward processing and use. In this work, we study some of the most challenging specialty optical fibers and their preforms. We analyze a hollow core photonic band gap fiber and its preforms, and bond quality at the joint between two fusion-spliced hollow core fibers. Additionally, we studied a multi-element optical fiber and a metal incorporated dual suspended-core optical fiber. The application of X-ray CT can be extended to almost all optical fiber types, preforms and devices.

Modified Powder-in-Tube Technique Based on the Consolidation Processing of Powder Materials for Fabricating Specialty Optical Fibers.

The objective of this paper is to demonstrate the interest of a consolidation process associated with the powder-in-tube technique in order to fabricate a long length of specialty optical fibers. This so-called Modified Powder-in-Tube (MPIT) process is very flexible and paves the way to multimaterial optical fiber fabrications with different core and cladding glassy materials. Another feature of this technique lies in the sintering of the preform under reducing or oxidizing atmosphere. The fabrication of such optical fibers implies different constraints that we have to deal with, namely chemical species diffusion or mechanical stress due to the mismatches between thermal expansion coefficients and working temperatures of the fiber materials. This paper focuses on preliminary results obtained with a lanthano-aluminosilicate glass used as the core material for the fabrication of all-glass fibers or specialty Photonic Crystal Fibers (PCFs). To complete the panel of original microstructures now available by the MPIT technique, we also present several optical fibers in which metallic particles or microwires are included into a silica-based matrix.

Observation of the Plateau-Rayleigh capillary instability in multi-material optical fibers

We report the observation of the Plateau-Rayleigh capillary instability during the tapering of a multi-material optical fiber. The fiber core is a glass, and the cladding is an amorphous polymer. The instability is manifested in the breakup of the core into a periodic string of size-tunable micro-scale droplets embedded along the fiber axis. The particle diameters may be tuned in the 1–20 μm range through control of the tapering speed and temperature. Extending this approach to the fabrication of polymer and glass nanoparticles appears feasible.