Specialised optical fibres have seen a significant resurgence in recent years, becoming essential optical components, designed to control and manipulate light guided within an optical network, enabling selective confinement, routing, dispersion or filtering to occur directly in the optical domain. Specialised optical fibres can be broadly classified as solid step or gradient index types, liquid core fibres and as photonic crystal or microstructure designs. In the former case, selective material doping of the fibres can afford unique properties that allow for optical amplification or photosensitivity. In the latter case, photonic crystal fibre allows for photon propagation in the most intricate of ways with great flexibility; we have far more control over the properties of photonic crystals than we do over the electronic properties of semiconductors. There are three key features that define the development of a specialised fibre i) the composition of the host material, ii) the waveguide design and iii) the use of specialised coatings.

This conference aims to provide a forum for scientists and engineers-involved with the modelling, design, fabrication, device integration, and application of PCFs and specialty optical fibres-to present and share their latest research and findings. This conference will expand on the existing innovations that relate to microstructure and speciality optical fibres, detailing progress in the areas of fibre manufacture, devices, and applications that target the fields of optical communications, fibre lasers and amplifiers, sensing and spectroscopy; and incorporating modelling of novel fibre geometries.

The conference program will consist of both oral and poster presentations. Papers are solicited on, but not limited to, the following topics:

  • • Materials, Processes and Fabrication Advances
  • Advances in speciality and microstructure fibre manufacture based on, silica, chalcogenide and multi-component glasses, rare-earth doped fibres, single crystal material fibre and polymer optical fibres, as well as new and advanced coating materials.

  • Theory and Modelling
  • Modelling and simulation of linear and nonlinear characteristics of novel optical fibres, including modal analysis, birefringence, polarisation and dispersion properties, confinement and bending losses, evanescent coupling in multi-core fibre and fibre tapers.

  • Test and Characterisation Methods
  • Characterisation of optical fibres, e.g. measurements of fibre geometry, birefringence, dispersion, non-linearity and distributed measurements.

  • Optical Components, Sensors and Devices
  • Speciality and microstructure fibre-based devices and their applications cover a broad spectrum of research areas that can include:
    We also encourage papers on hot topics and fields of commercial interest such as "Optical Nanowires and Sub-wavelength Diameter Fibres", "Mid-IR and Infrared Fibres", “Active fibres for fiber lasers”, "Specialty Fibres for Bio and Chemical Sensing" with initiatives and advances regarding covid-19 related research considered of primary interest, "Fibres for Harsh Environments", "Fibres for use in the Aerospace Industry", "Fibres for Oil and Gas Applications", and "Optical Fibres in Renewal Energy Applications".;
    In progress – view active session
    Conference 11773

    Micro-structured and Specialty Optical Fibres VII

    On demand now
    View Session ∨
    • Special Focus: Three Pillars of ELI Research Infrastructure-World's Most Advanced Short-pulse Lasers
    • Welcome and Monday Plenary Presentation I
    • Monday Plenary Presentation II
    • Tuesday Plenary Presentation III
    • Tuesday Plenary Presentation IV
    • Wednesday Plenary Presentation V
    • Thursday Plenary Presentation VI
    • Optical Fiber Technology I
    • Optical Fiber Technology II
    • Topical Discussion and Networking Forum Session
    • 1: Photonic Crystal Fibers and Hollow Core Fibers
    • 2: Active Fibers for Fiber Lasers I
    • 3: Active Fibers for Fiber Lasers II
    • 4: Fiber Gratings
    • 5: Optical Fiber Metrology and Sensing
    • 6: Optical Fiber Metrology and Polymer Optical Fibers
    • Poster Session
    Special Focus: Three Pillars of ELI Research Infrastructure-World's Most Advanced Short-pulse Lasers
    Livestream: 19 April 2021 • 09:00 - 11:05 CEST | Zoom



    9:00 to 9:05
    Welcome and Introduction
    Bedřich Rus, ELI Beamlines, Institute of Physics of the CAS (Czech Republic)
    Symposium Chair

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    Click
    here for Status of lasers and experiments at ELI-Beamlines
    here for ELI ALPS: the next generation of attosecond sources
    here for Status of high-power lasers and experiments at ELI-Nuclear Physics, Romania
    to now view in the SPIE Digital Library.
    11777-501
    Author(s): Georg Korn, ELI Beamlines (Czech Republic)
    On demand | Presented Live 19 April 2021
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    We are reviewing the high-average and high peak-power fs-laser sources and experimental areas currently in operation and preparation for user operation. This includes the 1 kHz, 15fs, 50mJ, Allegra laser based on OPCPA-technology. Short pulse 5ps-CPA thin disc lasers pump a series of OPCPA crystals ensuring a high contrast output. The Allegra laser enters the experimental area E1 with a number of end-stations for user experiments. The HAPLS (sub-30fs, Ti: Sapphire) laser pumped by a high-average power frequency converted DPSSL is currently delivering 500 TW, 3.3 Hz pulses via a stable vacuum beam transport system with a pointing stability around 1rad to the experimental areas for plasma physics experiments (E3) and ion acceleration (E4) with the ELIMAIA station. Both areas are fully equipped with target chambers and focusing optics for experimental operation and user assisted commissioning. The Nd:Glass laser Aton provides 1.5 kJ pulses and is currently being compressed to 10 PW in a large compressor tank. A second oscillator allows shaped pulse ns-operation at kJ level or future combination of 1 PW pulses and kJ shaped ns-pulses for advanced WDM or fusion experiments in the E3 area. A new laser disc liquid cooling technology enables repetition rates of 1 shot/minute allowing a much higher data acquisition for this kind of experiments. Furthermore we will report on the first experiments and the future experimental plans as well as on the prospects for user operation.
    11777-502
    Author(s): Katalin G. Varju, Univ. of Szeged (Hungary)
    On demand | Presented Live 19 April 2021
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    The Extreme Light Infrastructure – Attosecond Light Pulse Source (ELI-ALPS), the Hungarian pillar of ELI, is the first of its kind that operates by the principle of a user facility, supporting laser based fundamental and applied researches in physical, biological, chemical, medical and materials sciences at extreme short time scales. This goal is realized by the combination of specialized primary lasers which drive nonlinear frequency conversion and acceleration processes in more than twelve different secondary sources. Any light pulse source can act as a research tool by itself or, with femtosecond synchronization, in combination with any other of the sources. Thus a uniquely broad spectral range of the highest power and shortest light pulses becomes available for the study of dynamic processes on the attosecond time scale in atoms, molecules, condensed matter and plasmas. The ground-breaking laser systems together with the subsequent outstanding secondary sources generate the highest possible peak power at the highest possible repetition rate in a spectral range from the E-UV through visible and near infrared to THz. The facility – besides the regular scientific staff - will provide accessible research infrastructure for the international scientific community user groups from all around the world. The attosecond secondary sources are based on advanced techniques of Higher-order Harmonic Generation (HHG). Other secondary sources provide particle beams for plasma physics and radiobiology. A set of state-of-the-art endstations will be accessible to those users who do not have access or do not wish to bring along their own equipment. Step by step the lasers are now commissioned, trialed and handed over for user operation. References S. Kuhn et al., “The ELI-ALPS facility: the next generation of attosecond sources.”, Topical Review, Journal of Physics B, 50 (2017) 132002
    11777-503
    Author(s): Kazuo A. Tanaka, Extreme Light Infrastructure Nuclear Physics (Romania)
    On demand | Presented Live 19 April 2021
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    Founded by the European Strategy Forum on Research Infrastructure (ESFRI), three state-of-art laser-based institutes in Romania, Hungary, and the Czech Republic were commissioned in the Extreme Light Infrastructure (ELI). Construction for the three sites started in 2012 and, as of 2020, all sites are operational. ELI-NP (Extreme Light Infrastructure: Nuclear Physics) is located 10km south of Bucharest in Romania. Its flagship installation is two beams of 10 PW, each providing 230 J output energy at a 23 fs laser pulse width. The capability to provide a 10 PW output was recently demonstrated in a live performance. We were able to show that the 10 PW laser shots can be delivered for 10 minutes at a rate of one shot every minute. A total of 230 Zoom participants worldwide, including Prof G Mourou and Prof D Strickland, the Physics Nobel Laureates in 2018, witnessed this breakthrough demonstration. An early experiment at the 100 TW laser station at ELI-NP has already been completed. We successfully demonstrated an electron acceleration of up to 300 MeV, either resulting in monoenergetic or broadband spectra, depending on the well controllable experimental conditions we set. Operations at the 1 PW and 10 PW experimental stations will start soon. External user access will be tested with the early and commissioning experiments and will be formulated coherently within the framework of the IMPULSE project guided by ELI-DC. Reference Current status and highlights of the ELI-NP program research program, KA Tanaka, K Spohr, D Balabanski, et al., Matter Rad. Extremes, 5, 024402 (2020): doi.10.1063/1.5093535
    Session PL1: Welcome and Monday Plenary Presentation I
    Livestream: 19 April 2021 • 15:00 - 16:00 CEST | Zoom
    Monday Plenary Presentation I and Monday Plenary Presentation II are part of the same webinar session with a break in between.

    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Opening Remarks
    Bedřich Rus, ELI Beamlines, Institute of Physics of the CAS (Czech Republic)

    This event occurred in the past. Click here to now view in the SPIE Digital Library.
    11775-601
    New technologies for new astronomy (Plenary Presentation)
    Author(s): John C. Mather, NASA Goddard Space Flight Ctr. (United States)
    On demand | Presented Live 19 April 2021
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    We’ve come a long way since 1609, from spectacle lenses to mirrors in space, from twitching frog legs to the Event Horizon Telescope observing a black hole. But far more is possible. On the ground, a new generation of optical telescopes is under construction, up to 39 m in diameter. Adaptive optics compensates for the turbulent atmosphere, but could work far better with an orbiting reference beacon in space. Bright chemiluminescent emission lines in the upper atmosphere interfere with observations, but could be blocked by fiber optic filters. Energy-resolving photon counting detectors promise far greater sensitivity. New ways of making mirrors offer far better resolution for space X-ray telescopes. Coronagraphs can suppress starlight enough to reveal exoplanets in direct imaging, or starshades can cast star shadows on telescopes to do the same thing. New generations of far IR detectors with large cryogenic telescopes in space can reveal the cool and cold universe. Radio telescopes on the quiet far side of the Moon can overcome the limits of the ionosphere and intense local interference to see events in the early universe as it heated up again after the Big Bang expansion cooled everything. Neutrino telescopes can see stars being shredded by black holes, and gravitational wave detectors see merging neutron stars and black holes. Atom wave gravimeters can measure the internal structure of planets and asteroids, and sample return missions are already bring back distant bits of the solar system. What will happen next? I don’t know but it will be glorious.
    Session PL2: Monday Plenary Presentation II
    Livestream: 19 April 2021 • 17:00 - 18:00 CEST | Zoom
    Monday Plenary Presentation I and Monday Plenary Presentation II are part of the same webinar session with a break in between.

    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Introduction
    Ivo Rendina, CNR/Istituto per la Microelettronica e Microsistemi (Italy)
    Symposium Chair

    This event occurred in the past. Click here to now view in the SPIE Digital Library.
    11770-602
    Author(s): Anna C. Peacock, Univ. of Southampton (United Kingdom)
    On demand | Presented Live 19 April 2021
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    The nascent field of semiconductor core fibres is attracting increased interest as a means to exploit the excellent optical and optoelectronic functionality of the semiconductor material directly within the fibre geometry. Compared to their planar counterparts, this new class of waveguide retains many advantageous properties of the fibre platforms such as flexibility, cylindrical symmetry, and long waveguide lengths. Furthermore, owing to the robust glass cladding it is also possible to employ standard fibre post-processing procedures to tailor the waveguide dimensions and reduce the optical losses over a broad wavelength range, of particular use for nonlinear applications. This presentation will review progress in the development of nonlinear devices from the semiconductor core fibre platform and outline exciting future prospects for the field.
    Session PL3: Tuesday Plenary Presentation III
    Livestream: 20 April 2021 • 15:00 - 16:00 CEST | Zoom
    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Introduction
    Saša Bajt, Deutsches Elektronen-Synchrotron (Germany)
    Symposium Chair
    11776-603
    Author(s): Nina Rohringer, Max-Planck-Institut für Physik komplexer Systeme (Germany)
    On demand | Presented Live 20 April 2021
    Show Abstract + Hide Abstract
    X-ray free-electron lasers, delivering x-ray pulses of femtosecond duration, are available for experiments for more than a decade and allow for hitherto unachievable x-ray intensities on sample, reaching up to 1021 W/cm2 for hard x-rays. At these intensities, the probability of a single atom or molecule to absorb a photon of an impinging x-ray pulse reaches unity. Moreover, several interactions of photons and matter within the duration of the x-ray pulse – nonlinear x-ray matter interactions – become possible, opening the pathway to nonlinear x-ray optics. For a macroscopic ensemble of atoms, molecules, nanometer-sized clusters or a solid, the interaction with a strongly focused x-ray beam can create macroscopic, highly excited states of matter, far from equilibrium. In particular, saturated absorption with a high-intensity x-ray pulse can result in transient states, present for roughly one femtosecond, with the characteristic feature, that every single atom in the interaction region is in a population inverted state with missing population in the innermost electronic shell. This macroscopic population inversion can lead to collective radiative decay mechanisms, such as amplified spontaneous emission or superfluorescence. In this presentation I will give you an overview over our experimental and theoretical investigations of these single-pass x-ray laser amplifiers in the x-ray spectral domain. I will address applications of this phenomenon in the area of chemical x-ray emission spectroscopy, a new concept of an x-ray laser oscillator, and will highlight recent theoretical developments to describe collective spontaneous emission in the x-ray spectral domain.
    Session PL4: Tuesday Plenary Presentation IV
    Livestream: 20 April 2021 • 17:00 - 18:00 CEST | Zoom
    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Introduction
    Bedřich Rus, ELI Beamlines, Institute of Physics of the CAS (Czech Republic)
    Symposium Chair
    11777-604
    Author(s): Gilliss Dyer, SLAC National Accelerator Lab. (United States)
    On demand | Presented Live 20 April 2021
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    The Matter in Extreme Conditions (MEC) instrument at LCLS pioneered the use of the hard X-ray free electron laser (XFEL) in combination with high-power optical lasers to advance high energy density science. Commissioned in 2012 as an open-access scientific capability, this application of the powerful XFEL diagnostic has driven a rich array of high-profile scientific results, providing new insight into atomic and structural properties of dynamic plasma and high-pressure material states. Aided in part by the success of MEC and other high power laser facilities, there has been a strong call from the research community over the past 5 years for increased national investments in high power lasers combined with existing national lab infrastructure. In response to a mission need statement from the US Department of Energy, Fusion Energy Sciences, SLAC has developed a conceptual design for a project to build a new HED science facility combining high rep-rate (10Hz) petawatt laser systems and high energy (1kJ) long pulse lasers with the LCLS XFEL. Combined with flexible and high efficiency experimental systems, this facility will enable a world-unique set of scientific capabilities complementing the new emerging generation of high-power laser facilities, including the pillars of ELI and new HED end stations at European XFEL and SACLA. In this talk, I will present an overview of the facility conceptual design and place it in the context of the growing field of high-power laser science.
    Session PL5: Wednesday Plenary Presentation V
    Livestream: 21 April 2021 • 17:00 - 18:00 CEST | Zoom
    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)

    Welcome and Introduction
    Ivo Rendina, CNR/Istituto per la Microelettronica e Microsistemi (Italy)
    Symposium Chair
    11775-605
    Author(s): Mona Jarrahi, UCLA Samueli School of Engineering (United States)
    On demand | Presented Live 21 April 2021
    Session PL6: Thursday Plenary Presentation VI
    Livestream: 22 April 2021 • 09:00 - 10:00 CEST | Zoom
    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Introduction
    Saša Bajt, Deutsches Elektronen-Synchrotron (Germany)
    Symposium Chair
    11776-606
    New research opportunities with FELs (Plenary Presentation)
    Author(s): Claudio Masciovecchio, Elettra-Sincrotrone Trieste S.C.p.A. (Italy)
    On demand | Presented Live 22 April 2021
    Session IS1: Optical Fiber Technology I
    Livestream: 22 April 2021 • 12:00 - 14:00 CEST | Zoom
    Session Chair: Ivan Kašík, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic)
    Times are all Central European Summer Time (UTC + 2:00 hours)

    Optical Fiber Technology I & II Industry Sessions focus on advanced fabrication methods of optical fibers and optical fiber components, and contain a series of tutorial and invited lectures.
    11773-101
    Author(s): Anirban Dhar, Central Glass and Ceramic Research Institute-CSIR (India)
    On demand | Presented Live 22 April 2021
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    A short piece of specialty optical fiber acts as the backbone of various fiber-based devices such as high-power laser, amplifier, sensor, etc. suitable for various applications like communication, medical diagnosis, industrial as well as advance basic research. The performance of this specialty optical fiber will depend on the selection of materials, fabrication process technology used, and suitable optimization of various process steps. Accordingly the fabrication of a good quality silica-based specialty fiber doped with suitable dopants in a reliable and repeatable manner is a key challenge from a technological viewpoint and will be briefly discussed.
    11773-102
    Author(s): Ryszard Buczynski, Lukasiewicz Research Network (Poland)
    22 April 2021 • 13:00 - 13:50 CEST
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    Application of nanostructures for the development of optical fibers allows to shape their optical properties. Dispersion, modal and polarization properties of the nanostructured fibers are determined with internal discrete nanostructure of the core composed of multiple types of glasses. We discuss the current state of the art of this early-stage concept for silica and soft glass fibers, and their possible applications. Experimental verification and technological aspects of development of proof-of-concept nanostructured fibers are demonstrated.
    Session IS2: Optical Fiber Technology II
    Livestream: 22 April 2021 • 15:00 - 17:00 CEST | Zoom
    Session Chair: Ivan Kašík, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic)
    Times are all Central European Summer Time (UTC + 2:00 hours)

    Optical Fiber Technology I & II Industry Sessions focus on advanced fabrication methods of optical fibers and optical fiber components, and contain a series of tutorial and invited lectures.
    11773-103
    Author(s): Pavel Honzátko, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic)
    On demand | Presented Live 22 April 2021
    Show Abstract + Hide Abstract
    Current trends in optical fibers will be reviewed such as fibrs with suppressed stimulated Brillouin scattering, silica hollow core optical fibers with extended spectral transmission range, transmission of giant pulses over hollow core fiber lasers, and hollow core fiber gas lasers.
    11773-104
    Author(s): Alexis Mendez, MCH Engineering LLC (United States)
    On demand | Presented Live 22 April 2021
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    Given their EM immunity, intrinsic safety, small size & weight, autoclave compatibility and capability to perform multi-point and multi-parameter sensing remotely, optical fibers and fiberoptic-based sensors are seeing increased acceptance and new uses for a variety of bio-medical applications—from laser delivery systems, to disposable blood gas sensors, to intra-aortic pressure probes, to digital X-rays to name a few. This tutorial will provide a broad overview on how optical fibers and fiber-based sensors are being utilized in the biomedical arena, highlighting their intrinsic characteristics, advantages and requirements. Key industry applications, challenges and trends will be discussed, along with their future prospect and overall commercial outlook.
    Topical Discussion and Networking Forum Session
    Livestream: 22 April 2021 • 17:00 - 17:30 CEST | Zoom
    Hosted by:
    Alexis Mendez, MCH Engineering LLC (United States)

    Join this open session with the conference chairs and speakers, pose your questions or follow up on discussion and questions asked earlier in the Optical Fiber Industry Session and topics covered by the conference 11773, Micro-structured and Specialty Optical Fibres VII. Become involved, meet new people with similar interests, and join us for this unique opportunity for some interesting networking and discussion. This session is not recorded.
    Session 1: Photonic Crystal Fibers and Hollow Core Fibers
    11773-1
    Author(s): Yazhou Wang, Abubakar I. Adamu, Technical Univ. of Denmark (Denmark); Md. Selim Habib, Florida Polytechnic Univ. (United States), Univ. of Central Florida (United States); Manoj K. Dasa, Technical Univ. of Denmark (Denmark); Christian R. Petersen, Technical Univ. of Denmark (Denmark), NORBLIS IVS (Denmark); J. Enrique Antonio-Lopez, Univ. of Central Florida (United States); Binbin Zhou, Peter Uhd Jepsen, Technical Univ. of Denmark (Denmark); Axel Schülzgen, Univ. of Central Florida (United States); Morten Bache, Technical Univ. of Denmark (Denmark); Rodrigo Amezcua Correa, Univ. of Central Florida (United States); Ole Bang, Technical Univ. of Denmark (Denmark), NKT Photonics A/S (Denmark), NORBLIS IVS (Denmark); Christos Markos, Technical Univ. of Denmark (Denmark), NORBLIS IVS (Denmark)
    On demand
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    We will present our recent work using noble and Raman-active gas-filled anti-resonant hollow-core fiber (ARHCF) technology. First, we will present the generation of supercontinuum spanning from 200 nm to 4000 nm based on nonlinear effects of soliton self-compression and phase-matched deep‑ultraviolet (DUV) dispersive wave (DW) emission in Argon (Ar)-filled ARHCFs pumped at 2.46 μm wavelength with 100 fs pulses and ~8μJ pulse energy. Then we will discuss our recent work on stimulated Raman scattering (SRS) effect in a hydrogen (H2)-filled ARHCF, to achieve near- and MIR Raman lasers. By employing the single-stage vibrational SRS effect, a 4.22 μm Raman laser line is directly converted from a linearly polarized 1.53 μm pump laser. A quantum efficiency as high as 74% was achieved, to yield 17.6 µJ pulse energy. The designed 4.22 μm wavelength is well overlapped with the strongest CO2 absorption, therefore constituting a promising way for CO2 detection. In addition, we report a multi-wavelength Raman laser based on the cascaded rotational SRS effect. Four Raman lines at 1683 nm, 1868 nm, 2100 nm, and 2400 nm are generated, with pulse energies as high as 18.25 µJ, 14.4 µJ, 14.1 µJ, and 8.2 µJ, respectively. The energy of these Raman lines can be controlled by tuning the H2 pressure from 1 bar to 20 bar.
    11773-44
    Author(s): Markus A. Schmidt, Torsten Wieduwilt, Malte Plidschun, Mona Nissen, Shiqi Jiang, Ronny Förster, Leibniz-Institut für Photonische Technologien e.V. (Germany)
    On demand
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    High-speed tracking of nano-objects is a gateway to understanding biological processes at the nanoscale. Here we will present our results on tracking single or ensembles of nano-objects inside optofluidic fibers via elastic light scattering. The nano-objects diffuse inside a channel of a microstructured fiber and the light scattered by the nano-object is detected transversely via a microscope. We will present the fundamentals of this approach and focus on selected results including retrieval of the full 3D trajectory of a diffusing nano-sphere, the simultaneous detection of hundreds of nano-objects in hollow core anti-resonant fibers and first results on inactivated SARS-CoV-2.
    11773-2
    Author(s): Paweł E. Kozioł, Piotr Jaworski, Wroclaw Univ. of Science and Technology (Poland); Fei Yu, Shanghai Institute of Optics and Fine Mechanics (China), Univ. of Chinese Academy of Sciences (China); Karol Krzempek, Wroclaw Univ. of Science and Technology (Poland); Dakun Wu, Shanghai Institute of Optics and Fine Mechanics (China), Univ. of Chinese Academy of Sciences (China); Grzegorz Dudzik, Viktoria Hoppe, Wroclaw Univ. of Science and Technology (Poland); Meisong Liao, Shanghai Institute of Optics and Fine Mechanics (China); Krzysztof M. Abramski, Wroclaw Univ. of Science and Technology (Poland)
    On demand
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    One of the main challenges of laser-based gas sensingis the development of sensors delivering simultaneously high sensitivity, selectivity, fast-response time and non-complex design. Mostly, the detection capability of such sensors depends on the interaction path length between the laser light and the measured gas. Hence, long optical paths are highly desired for e.g. low-concentration gas sensing. Our proposal is to use Antiresonant Hollow-Core Fibers (ARHCFs), which filled with the target gas mixture form absorption cells with potentially any length, delivering low-volume, long and versatile optical paths within the sensor configuration. Currently, the ARHCF core is filled with the target gas via specially designed bulk-optics-based cells placed at the fiber’s ends. This solution provides relatively fast fiber core filling time, however being only efficient while an overpressure is used to force the gas flow through the core, not the diffusion. Therefore, searching for alternative ways of fiber filling with the target gas is necessary. We propose a method of processing the fiber structure using a femtosecond laser allowing for non-invasive accessing the fiber core for more efficient and faster gas diffusion into it through the fabricated microchannels. The fiber structure modification was optimized in a way that does not introduce any unwanted damage of the fiber e.g. cracks on the glass parts or cladding capillaries. The performed experiments have indicated that the laser-processing of the ARHCF structure introduces negligible transmission loss regardless of the number of fabricated microchannels and their length (0.2dB loss for 25 microchannels), confirming the proposed method suitability.
    11773-3
    Author(s): Oleh Yermakov, ITMO Univ. (Russian Federation), V. N. Karazin Kharkiv National Univ. (Ukraine); Henrik Schneidewind, Uwe Hubner, Torsten Wieduwilt, Matthias Zeisberger, Leibniz-Institut für Photonische Technologien e.V. (Germany); Andrey Bogdanov, ITMO Univ. (Russian Federation); Yuri Kivshar, The Australian National Univ. (Australia), ITMO Univ. (Russian Federation); Markus A. Schmidt, Leibniz-Institut für Photonische Technologien e.V. (Germany), Friedrich-Schiller-Univ. Jena (Germany)
    On demand
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    Coupling of light to optical fibers is important for many applications, while for commonly used step-index optical fibers it massively drops for oblique incident angles >15 degrees, limiting their operational range to a narrow angle interval. In this work, we address this issue via inclusion of high-index all-dielectric concentric ring-type nanostructures located in the core region of commercially available step-index fibers. These nanostructures with different number of rings have been implemented on fiber end faces via planarization and electron beam lithography. Acting as axial-symmetric diffraction gratings, they open the additional diffraction channels. Thus, matching the phase distributions of scattered field and core mode, light couples from free space to fibers much more efficient. Modification of fiber facet with the optimized ring nanostructure leads to polarization- and azimuthally-independent enhancement of in-coupling efficiency across the entire angle interval from 15 to 85 degrees. Measurements show percent-level of light in-coupling efficiency even at angles as large as 80 degrees, addressing a domain that is out-of-reach for fibers with unstructured end faces. The main result of this work is the enhancement of the in-coupling efficiency at large incident angles (>60 degrees) by 4 orders of magnitude with respect to a bare fiber. Fibers empowered by all-dielectric nanostructures indicate a significant improvement reaching unprecedented levels of in-coupling efficiency and outperforming the fibers with plasmonic nanostructures and unstructured end faces. The results obtained are promising for any application that demands to remotely collect light under large angles, such as in-vivo spectroscopy, biosensing or quantum technology.
    11773-4
    Author(s): Aleksandra Matrosova, S. I. Vavilov State Optical Institute (Russian Federation), ITMO Univ. (Russian Federation); Natalia Kuzmenko, ITMO Univ. (Russian Federation); Sergey Evstropiev, S. I. Vavilov State Optical Institute (Russian Federation), ITMO Univ. (Russian Federation), Saint-Petersburg State Institute of Technology (Russian Federation); Vladimir Aseev, ITMO Univ. (Russian Federation); Grigory Pchelkin, S. I. Vavilov State Optical Institute (Russian Federation), Peter the Great Saint-Petersburg Polytechnic Univ. (Russian Federation); Vladimir Demidov, S. I. Vavilov State Optical Institute (Russian Federation); Nikolay Nikonorov, ITMO Univ. (Russian Federation)
    On demand
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    An objective of this study was to develop the prototype of an active optical fiber with highly luminescent Gd2O3:Nd3+ nanophosphors dispersed in a silica glass matrix. The main idea consisted in using a silica microcapillary preform for the hollow-core anti-resonant optical fiber containing Gd2O3:Nd3+ nanophosphors preliminary grown on the surfaces of the capillaries. The formation of Gd2O3:Nd3+ nanophosphors inside the cavities of the preform was performed through the impregnation of the preform with a modifying solution. The architecture of the hollow-core anti-resonant optical fiber provides a relative simplicity of impregnating the preform due to the limited amount and large inner diameter of the capillaries. Basic requirement for such an element is the functionality simultaneously within two separate spectral ranges – the excitation wavelength range near 532 nm and the emission wavelength range near 1064 nm. The polymer-salt method was applied to synthesize film-forming solutions with high adhesion to the surface of a silica glass based on aqueous solutions of Gd(NO3)3, NdCl3 and a soluble organic polymer (polyvinylpyrrolidone). It was determined that post-processing of the liquid composition at 1000-1050 °C allows obtaining Gd2O3:Nd3+ nanophosphors with a size of 25-42 nm and a cubic crystal structure. Characterization of the preforms and optical fibers modified with Gd2O3:Nd3+ nanophosphors was conducted by XRD, SEM, optical microscopy and photoluminescence analysis. It was found out that the hollow-core anti-resonant optical fibers doped with Gd2O3:Nd3+ nanophosphors demonstrate photoluminescence properties characteristic to Nd3+ ions in metal sesquioxides. In addition, it was revealed that luminescence kinetics of optical fibers is described by two exponential dependences with decay times τ1 = 12 μs and τ2 = 233 μs what can be attributed to the feature of a cubic crystal structure of Gd2O3.
    11773-5
    Author(s): Radan Slavik, Eric R. Numkam Fokoua, Meng Ding, Zitong Feng, Francesco Poletti, David J. Richardson, Optoelectronics Research Ctr. (United Kingdom)
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    Hollow core optical fibres have many unique properties, especially compared to traditional glass-core optical fibres [1]. Firstly, the light path is accessible and light can thus interact with the gas inside over long lengths, making them interesting for applications in gas sensing or for nonlinear processes in gasses. Hollow core fibres can also operate at wavelengths, where silica glass has poor transmission and their chromatic dispersion is not compromised by the chromatic dispersion of bulk glass. Yet another unique feature is weak interaction of light with the guiding medium (typically air), significantly increasing the damage threshold and thus making them a good candidate for high-power (average or peak power) light delivery. Another group of unique features is related to how their properties (little) change with temperature. In the presentation, we will firstly show where the common fibre optics wisdom (gained from work with standard optical fibres) tends to fail. In the second part, we will discuss how differently hollow core fibre change with temperature as compared to standard optical fibres and how it can be used for various applications, including fibre interferometry and time-stable signal transmission.
    11773-6
    Author(s): Grzegorz Gomolka, Wroclaw Univ. of Science and Technology (Poland); Grzegorz Stępniewski, Univ. of Warsaw (Poland); Dariusz Pysz, Institute of Electronic Materials Technology (Poland); Ryszard Buczynski, Mariusz Klimczak, Univ. of Warsaw (Poland); Michal Nikodem, Wroclaw Univ. of Science and Technology (Poland)
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    Trace gas detection plays significant role in environmental monitoring, medical diagnostics and industrial process control. Laser absorption spectroscopy is a frequently used approach, because it exhibits great selectivity, large flexibility and sensitivity down to ppm or even ppb levels, depending on molecule, method and absorption band used for detection. In the typical sensing systems, the sensitivity can be improved by increasing the light-matter interaction path length. This is usually accomplished with multi-pass cells. Alternative approach is to use hollow core fiber (HCF) as gas cell. This has some advantages such as opto-mechanical and thermal stability, robustness, small size and weight and low attenuation. Here we will present our recent experiments on laser-based detection of methane inside anti-resonant (AR) HCF. We will demonstrate methane detection in two spectral regions, in the mid- and the near-infrared, using silica-based AR HCFs (1.3-m and 6.5-m-long) as gas cells. Wavelength modulation spectroscopy (WMS) technique was employed, and the detection limits below 100 ppm and below 1 ppm was obtained for the near-infrared and the mid-infrared setup, respectively. In the presentation the experimental details, detection limits and advantages and drawbacks of different sensing approaches will be presented.
    Session 2: Active Fibers for Fiber Lasers I
    11773-7
    Author(s): Konstantin K. Bobkov, A. M. Prokhorov General Physics Institute (Russian Federation); Svetlana S. Aleshkina, Maxim M. Khudyakov, A. M. Prokhorov General Physics Institute (Russian Federation); Denis S. Lipatov, G.G. Devyatykh Institute of Chemistry of High-Purity Substances (Russian Federation); Mikhail E. Likhachev, A. M. Prokhorov General Physics Institute (Russian Federation)
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    In the recent years high peak power ultra-fast fiber lasers become an important tool for industry. However standard optical fibers have a low threshold of non-linear effects, which limits maximum achievable peak power and therefore possible applications of pulsed fiber lasers. Different types of large-mode-area (LMA) fibers were designed to overcome this restriction. Typically, it is based on few-modes large diameter core approach, where high-order-modes (HOMs) are suppressed by different methods (bending, differential amplification, excess HOMs loss). However possibility of HOMs propagation in LMA fibers results in an appearance of undesirable effects such as amplification of cladding modes, transverse mode instability effect and long-term mode shape degradation issues. To date one of the most promising LMA fiber designs is active tapered fibers. Its core and first cladding diameters smoothly increase along the fiber length to several times from their original size. If only fundamental mode is excited at the thin end (typically single mode) no excitation of HOMs occurs during light propagation toward to the thick fiber end. The approach insures both diffraction-limited output beam quality and a high threshold of nonlinear effects. Moreover, large first cladding size at the thick tapered fiber end allows high pump powers to be introduced into the fiber, which makes possible amplification of the signal to a high average power. In the current paper we discuss current state of the art in the field of tapered fiber development. The best results in term of high peak and high average power achieved with this type of fibers are presented together with requirements to the tapered fiber amplifier design. The report is mainly focused on tapered fiber amplifiers operated near 1 um (Yb-doped tapered fibers), but also extension of this technique to 1.55 um spectral range will be discussed.
    11773-8
    Author(s): Denis S. Lipatov, Mikhail V. Yashkov, Alexey N. Abramov, G.G. Devyatykh Institute of Chemistry of High-Purity Substances (Russian Federation); Andrey A. Umnikov, G.G. Devyatykh Institute of Chemistry of High-Purity Substances (Russian Federation); Aleksey N. Guryanov, G.G. Devyatykh Institute of Chemistry of High-Purity Substances (Russian Federation); Konstantin K. Bobkov, Mikhail M. Bubnov, A. M. Prokhorov General Physics Institute (Russian Federation); Mikhail E. Likhachev, A. M. Prokhorov General Physics Institute (Russian Federation)
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    Highly-Yb doped fibers are of great interest for single frequency fiber lasers, where a very short resonator (with small number of longitudinal modes) is required and laser efficiency is limited by pump absorption at the short fiber length required for resonator. Another promising application is fibers for high peak power amplifiers, where high Yb concentration together with pedestal technique would allow one to design ultra-short large mode area fibers. In the current communication we study limitation for maximum Yb concentration in silica based fibers. Two most popular glass matrix (F-Al2O3-SiO2 and Al2O3-P2O5-SiO2) are studied. Possibility to introduce ultra-high doping level of Yb2O3 (in excess of 2.5 mol.%) with a very low optical loss was demonstrated. At the same time it was shown that at very high Yb concentration in the core fibers with very low grey loss (both initial and induced by photodarkening) can nearly completely lose its active properties. Reasons for the observed effect will be discussed at the conference. Optimal glass matrixes and optimal concentration of Yb in the core, which allow keeping active properties of the fiber was studied. As a result fiber based on Al2O3-P2O5-SiO2 glass matrix and doped with 1.2 mol.% of Yb2O3 (absorption was about 1000 dB/m at 920 nm)was fabricated and studied. Ultra-short amplifier based on the fabricated fiber was build. Perspectives for fabrication of highly-efficient single frequency fiber lasers based on such fiber as well as possibility to develop pedestal-based large mode area fiber with similar core compound are discussed.
    11773-9
    Author(s): Mikhail I. Skvortsov, Institute of Automation and Electrometry (Russian Federation); Victor I. Labuntsov, Institute of Automation and Electrometry (Russian Federation), Novosibirsk State Univ. (Russian Federation); Alexey A. Wolf, Institute of Automation and Electrometry (Russian Federation), Novosibirsk State Univ. (Russian Federation); Alexandr V. Dostovalov, Institute of Automation and Electrometry (Russian Federation); Sergey A. Babin, Institute of Automation and Electrometry (Russian Federation), Novosibirsk State Univ. (Russian Federation)
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    We report on the demonstration and characterization of Raman laser generating at the wavelength of ~1090 nm with total output power of up to 5 W based on the 7-core passive fiber with coupled cores. The Raman gain in all cores is provided by the pump laser connected to the FBG-free central core, whereas the laser cavity is formed by two sets of highly-reflective fiber Bragg gratings (FBGs) inscribed by fs pulses in all peripherical cores at the both ends of the 7-core fiber. The output FBG set has got a random shift along the axis between individual FBGs thus forming a random array of FBGs. Along with the Stokes line narrowing reasoned by the reduction of spectral broadening via nonlinear effects due to the enlargement of effective mode area in the multicore fiber with coupled cores in comparison with a standard singlemode fiber Raman laser, the additional line narrowing effect induced by the multicore random FBG array has been also revealed. It results in the generation of single peak of <30 pm linewidth near the threshold, whereas the linewidth broadens to ~250 pm at maximum power. At that, the single peak generation at low powers is not stable in time converting at some moments to multiple 20-pm peaks with random spacing and amplitudes defined by the interference of beams reflected from individual output FBGs with random longitudinal shifts. The ways to stabilize the generated spectrum are discussed.
    11773-10
    Author(s): Michal Kamradek, Pavel Peterka, Jakub Cajzl, Petr Varak, Jan Aubrecht, Ondřej Podrazký, Pavel Honzátko, Ivan Kašík, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic)
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    Thulium-doped fiber lasers (TDFL) are currently in focus of intense research worldwide with a great application potential in a spectral region around 2 μm. Their broad utilization includes among others medicine, defense or material processing. TDFL are in foreground of the interest especially thanks to a thulium energy level structure which enables a so-called two-for-one cross-relaxation (CR) process. This CR process presents a way to generate two photons at 2 μm from one pump photon at around 790 nm, and thus it allows to efficiently generate emission at 2 μm from available high brightness laser diodes emitting around 790 nm. Although the CR process is very promising and high-power fiber lasers based on it have already been presented, there are still reserves in its practical exploitation. In order to push the practical limits, reliable theoretical models are necessary. Among all parameters needed for the modelling, those describing energy transfers (ET) between thulium levels pose the main uncertainty. In this contribution, we present a method of energy transfer coefficients evaluation using rate equation modelling. This approach was based on a set of rate equations relating populations of energy levels with spectroscopic data. The coefficients were derived from fluorescence measurements by fitting fluorescence decay curves with theoretical equations. Studied fibers were pumped at two wavelengths – 793 nm and 1620 nm. Fluorescence curves were collected at 800 nm and 2 μm. All combinations of pumping and fluorescence measurements were examined for various pump power in a range up to 70 mW. Calculated energy transfer coefficients will be used in theoretical investigations and optimization of thulium-doped silica-based fiber lasers.
    Session 3: Active Fibers for Fiber Lasers II
    11773-12
    Author(s): Jaesun Kim, Taihan Fiberoptics Co., Ltd. (Korea, Republic of); Gaye Park, Taihan FiberOptics Co. Ltd. (Korea, Republic of); Seongmin Ju, Taihan FiberOptics Co., Ltd. (Korea, Republic of); Jaewan Han, Chanho Hwang, Hyunjoo Kim, HyeYeon Lee, Junho Lee, Taihan Fiberoptics Co., Ltd. (Korea, Republic of); Byungjoo Kong, Taihan FiberOptics Co., Ltd. (Korea, Republic of); Changhyun Jung, Taihan Fiberoptics Co., Ltd. (Korea, Republic of); Seunghyun Park, Taihan FiberOptics Co., Ltd. (Korea, Republic of)
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    Active gain fiber is a key component to realize high power fiber laser sources for various applications such as material processing, communications and optical sensing. To meet the requirement of the various applications, there are still many challenges for the fabrication of active gain fibers. Conventional method to fabricate active gain fibers is typically based on MCVD (Modified Chemical Deposition) with solution or vapor doping of rare-earth ions. This technology general shows some drawbacks in terms of the fabrication of large core and homogeneity of core’s refractive index. To resolve this, the novel VAD technology for active gain fibers will be proposed and several experimental results of large core fibers with a significantly improved homogeneity of refractive index profile will be presented.
    11773-13
    Author(s): Antreas Theodosiou, Lumoscribe Ltd. (Cyprus); Jan Aubrecht, Pavel Peterka, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic); Kyriacos Kalli, Cyprus Univ. of Technology (Cyprus)
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    We investigating how the physical dimensions of a fiber Bragg grating (FBG) may affect the performance of a monolithic fiber laser system. In particular, we perform a series of inscriptions in a Holmium-doped single mode fiber using the plane-by-plane femtosecond laser inscription method, using exactly the same inscription conditions but having different grating widths. Specifically, the gratings were divided in to three groups; group 1, gratings inscribed with planes having widths smaller of the core size but in the center of the fiber; group 2, gratings inscribed with plane widths similar to the core diameter and group 3, gratings with plane widths larger the core diameter that were extended uniformly in to cladding region. All the gratings were characterized in a fiber laser configuration and their performance were analyzed using as metrics the threshold power, the effective length and the power slope efficiency. We note that all the gratings were designed to have a resonance Bragg wavelength at 2.1 μm, having the same length and inscribed directly through the fiber coating. The monolithic fiber laser strands were pumped using Thulium-doped fiber laser operating at 1.95 μm. The results clearly show that the spatial dimensions of the FBGs are certainly an important parameter that is required for consideration during the development of the monolithic fiber lasers, especially for medium and high-power fiber laser systems.
    11773-14
    Author(s): Grzegorz Gomolka, Monika Krajewska, Wroclaw Univ. of Science and Technology (Poland); Aleksandr Khegai, Sergey Alyshev, A. M. Prokhorov General Physics Institute (Russian Federation); Aleksey Lobanov, G.G. Devyatykh Institute of Chemistry of High-Purity Substances (Russian Federation); Sergei Firstov, A. M. Prokhorov General Physics Institute (Russian Federation); Michal Nikodem, Wroclaw Univ. of Science and Technology (Poland)
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    Development of optical fiber amplifiers for the spectral band from 1600 to 1800 nm is still a vital issue. Semiconductor optical amplifiers (SOAs) and Tm-doped fiber amplifiers (TDFAs) show promising performance in this spectral region, however some limitations still occur, e.g. the output power levels typically do not exceed few tens of milliwatts. Higher optical powers may be particularly useful in some applications, e.g. gas sensing, e.g. methane has relatively strong absorption line at 1651 nm, that is often used for sensing at trace levels. In this presentation we will present the bismuth-doped fiber amplifier (BDFA) setup that operates between 1630 and 1730 nm. The amplifier uses the 90-m long bismuth-doped germanosilicate fiber. The pump source comprises the 1550 nm Er-doped fiber laser seed amplified with an Er/Yb-doped fiber amplifier. Pump power as high as 32 dBm (~1.6 W) can be supplied. The setup was analyzed at four wavelengths. We used single frequency sources at 1630, 1651 and 1687 nm and also home-made bismuth-doped fiber laser centered at 1730 nm. Small signal gain values (input power of -20 dBm) of 21.2 dB at 1651 nm and 27.5 dB at 1687 nm were obtained. For higher input powers (few milliwatts), the output powers of 180 mW at 1651 nm and 230 mW at 1687 nm were achieved.
    11773-15
    Author(s): Nadia Giovanna Boetti, LINKS Foundation (Italy); Diego Pugliese, Politecnico di Torino (Italy), RU INSTM (Italy); Omri Moschovits, Ben-Gurion Univ. of the Negev (Israel); Enkeleda Balliu, Mid Sweden Univ. (Sweden); Joris Lousteau, Politecnico di Milano (Italy), RU INSTM (Italy); Duccio Gallichi-Nottiani, Politecnico di Torino (Italy), Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (Italy); Davide Janner, Politecnico di Torino (Italy), RU INSTM (Italy); Amiel Ishaaya, Ben-Gurion Univ. of the Negev (Israel); Magnus Engholm, Mid Sweden Univ. (Sweden); Daniel Milanese, Univ. degli Studi di Parma (Italy), RU INSTM (Italy)
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    In recent years, there has been a growing interest towards compact high peak-power pulsed laser sources for applications such as LIDAR, range findings, remote sensing, communications and material processing. A common laser architecture used to realize these sources is the Master Oscillator Power Amplifier (MOPA), in which a master oscillator produces a highly coherent beam and a fiber amplifier boosts the output power, while preserving its main spectral properties. Phosphate glasses are recognized to be an ideal host material for engineering the amplification stage of a pulsed MOPA since they enable extremely high doping levels of rare-earth ions to be incorporated in the glass matrix without clustering, thus allowing the fabrication of compact active devices with high gain per unit length. With the aim of realizing compact optical fiber amplifiers operating at 1 and 1.5 µm, a series of highly Yb3+- and Yb3+/Er3+-doped custom phosphate glass compositions were designed and fabricated to be used as active materials for the core of the amplifiers. Suitable cladding glass compositions were explored and final core/cladding glass pairs were selected to realize single-mode and multi-mode optical fibers. Core and cladding glasses were synthesized by melt-quenching technique. The core glass was then cast into a cylindrical mold to form a rod, while the cladding glass was shaped into a tube by rotational casting method or extrusion technique. The latter has been extensively employed for the manufacturing of tellurite and germanate glass preforms, but only recently the first example of active phosphate fiber preform fabricated by this method has been reported by our research team. Phosphate fibers were then manufactured by preform drawing, with the preform being obtained by the rod-in-tube technique. Preliminary results of pulsed optical amplification at 1 and 1.5 µm are presented for a single-stage MOPA.
    11773-16
    Author(s): Lukasz Pajewski, Wroclaw University of Science and Technology (Poland); Slawomir Sujecki, The Univ. of Nottingham (Poland); Lukasz Sojka, Wroclaw University of Science and Technology (Poland); Angela Seddon, Trevor Benson, Mark Farries, David Furniss, The Univ. of Nottingham (United Kingdom); Samir Lamrini, LISA Laser (Germany)
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    Fluoride glass fibers have many applications related to handling light at wavelengths that exceed 2000 nm. In particular, fiber lasers operating at wavelengths stretching from 2000 nm to nearly 4000 nm can be effectively realised using fluoride glass fibers. A wide range of wavelengths, high output beam quality and ease of beam handling predestines lanthanide ion doped fluoride glass fiber lasers to applications in medicine, environment monitoring and infrared imaging. The pump lasers’ operating wavelengths are typically within the near-infrared wavelength range and can be in most cases implemented using standard semiconductor laser technology, which greatly improves reliability of the realised light sources and reduces the cost. In this contribution the design and realisation of lanthanide ion doped, fluoride glass fiber lasers are discussed. The considered dopant ions are dysprosium (III) and erbium (III). In the case of erbium (III) ion wavelengths near, and below, 3000 nm were achieved whilst for dysprosium (III) ion doping wavelengths beyond 3000 nm were obtained. Both continuous wave and pulsed laser operation has been considered. To achieve pulsed operation two techniques have been implemented: Q-switching and gain switching. The obtained pulses have a pulse duration from microseconds down to 70 ns. The typical pulse repetition rates are in the kilohertz range. The analysis of the experimentally observed pulses is complemented here by the presentation of numerically obtained results. The numerical results were obtained using an in-house developed software suite for fast and efficient time domain analysis of fluoride glass fiber lasers and is based on a specially tailored implementation of the method of lines.
    Session 4: Fiber Gratings
    11773-17
    Author(s): Antreas Theodosiou, Lumoscribe Ltd. (Cyprus); Arnaldo Leal, Univ. Federal do Espírito Santo (Brazil); Carlos Marques, Univ. de Aveiro (Portugal); Anselmo Frizera, Univ. Federal do Espírito Santo (Brazil); Antonio Fernandes, Univ. de Aveiro (Portugal); Andrei Stancalie, Institutul National pentru Fizica Laserilor, Plasmei si Radiatiei (Romania); Andreas Ioannou, Cyprus Univ. of Technology (Cyprus); Daniel Negut, Institutul National pentru Fizica Laserilor, Plasmei si Radiatiei (Romania); Kyriacos Kalli, Cyprus Univ. of Technology (Cyprus)
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    We consider a comparative study of radiation effects (γ and electron) on fibre Bragg gratings (FBGs) that were inscribed using a femtosecond laser in single mode silica optical fibre. The FBGs were inscribed using the point-by-point and the plane-by-plane inscription methods. The FBGs were exposed to a total accumulated radiation dose of 15 kGy in both γ and electron cases. The gratings’ spectra were measured and analysed before and after the exposure to the radiation, while complementary characterisation was undertaken using Raman and Fourier transform infrared spectroscopy. In addition, the changes of the temperature coefficient of the FBGs were analysed comparatively prior to the irradiation to explain how material changes responded to the particular types of radiation. Finally, we consider which of the two inscription methods proves more robust in such harsh environments.
    11773-18
    Author(s): Andreas Ioannou, Aristi Christofi, Sotia Zavrou, Kyriacos Kalli, Cyprus Univ. of Technology (Cyprus); David A. Jackson, Univ. of Kent (United Kingdom); Wern Kam, Univ. of Limerick (Ireland); Peter Woulfe, Galway Clinic (Ireland); Sinead O’Keeffe, Univ. of Limerick (Ireland); Francis J. Sullivan, National Univ. of Ireland (Ireland)
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    We present simple and robust designs for optical fiber radiation sensors for dosimetry applications, focusing on improved light gathering efficiency. More specifically, we examined the implementation of compound parabolic concentrators (CPC) using scintillator-based optical fibers. The fabrication of the parabolic concentrator is achieved by femtosecond micromachining at the end face of the polymer fiber. Furthermore, we consider the luminous properties of Gadolinium Oxysulfide (GADOX), an inorganic compound usually used in ceramic scintillators, as an alternative and combine it with laser-shaped polymer optical fibers (POF). The simplicity and ease of implementation of the sensor designs offers the prospect of distributed sensors; adding a wavelength shifting element is discussed to make the sensor more adaptable depending on the selected interrogation system.
    11773-19
    Author(s): Lennart Leffers, Julia Locmelis, Kort Bremer, Bernhard Roth, Ludger Overmeyer, Leibniz Univ. Hannover (Germany)
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    We report on a new and very simple sensor concept to quantify bending in 3D. The concept relies on the inscription of eccentrical Bragg gratings into perfluorinated, graded-index, multimode polymer optical fibre cores via contact exposure with a krypton fluoride excimer laser in the ultraviolet region and an optimized phase mask. This results in a sensor with high elasticity and flexibility to be utilized in applications where glass sensors fail to operate correctly. The sensor can detect bending or shape deformation in 3D. Depending on the polymer optical fibre deformation radius, the lattice constant of the inscribed Bragg grating is strained or compressed due to its position relative to the fibre core. This in turn results in a shift of the Bragg wavelength of up to 1.3 nm to the red or blue wavelength region, respectively. Deformation along one axis can be observed with a single Bragg grating with a sensitivity of 50 pm/m-1. Apart from the Bragg wavelength position, the peak intensity also changes with deformation, since the light is mainly guided in the outer region of the waveguide core. This allows simple bend detection using a narrow light source and a powermeter. Multiple Bragg gratings inscribed into the same polymer optical fibre from different angles, but at the same position allow to quantify the bending of the fibre in 3D relative to a reference frame. Consequently, this technology could form the basis for new applications in the areas of medical diagnostics, robotics, augmented reality and motion capture technologies.
    11773-20
    Author(s): Aviran Halstuch, Amiel Ishaaya, Ben-Gurion Univ. of the Negev (Israel)
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    Femtosecond induced refractive index change in transparent materials has been under extensive research in the past two decades. One of the major research areas in this field is femtosecond inscription of fiber-Bragg-gratings (FBGs) with the phase-mask (PM) technique. This technique is found to be robust and efficient. Here, we introduce a new method for inscribing phase-shifted-gratings in an optical fiber with femtosecond pulses and a suitable PM. The method is based on inscribing two slightly shifted FBGs, one over the other, with a slight Bragg wavelength shift between the two. The inscription setup consists of a NIR femtosecond laser, a PM, a defocusing spherical lens and a cylindrical focusing lens. A first FBG is inscribed, while the second overlapping FBG is inscribed only after a slight movement of the PM, enabling a slight Bragg wavelength shift. The transmission spectrum of this complex structure is like that of a phase-shifted-grating, yet the fabrication process is fast and simple compared to most other methods. High-quality phase-shifted-grating with two −20dB transmission dips, a 15dB transmission peak, with a 30 pm transmission bandwidth at 3dB is achieved. In addition, we show that different PM movements before the second inscription results in different Bragg wavelength shifts. This in turn results in a different phase-shifted grating structure. So that by controlling the movement of the PM in the second step, it is possible to inscribe phase-shifted gratings with different transmission spectra. We also observe that our phase-shifted-grating structures is birefringent.
    11773-22
    Author(s): Ricardo E. da Silva, Egor Manuylovich, Namita Sahoo, Aston Univ. (United Kingdom); Martin Becker, Manfred Rothhardt, Hartmut Bartelt, Leibniz-Institut für Photonische Technologien e.V. (Germany); David J. Webb, Aston Univ. (United Kingdom)
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    High efficiency acousto-optic modulation of a fibre Bragg grating is achieved by means of a compact acousto-optic device for the first time. The modulator is composed of millimetre scaled components and a 1cm grating inscribed in a four air holes highly birefringent suspended core fibre. The reflection of the orthogonal polarization modes is tuned by a sinusoidal electrical signal at the resonance frequency of 469 kHz. A significant modulation depth of 45% is achieved at a maximum drive voltage of 10 V. The demonstrated 4 cm long all-fibre acousto-optic device is 60% shorter compared to previous similar setups, indicating new possibilities for stable and fast modulation of fibre-integrated photonic devices.
    Session 5: Optical Fiber Metrology and Sensing
    11773-23
    Author(s): Garry Berkovic, Shlomi Zilberman, Ehud Shafir, Yosef London, M. Dadon, Soreq Nuclear Research Ctr. (Israel); M. Alefe, K. Ben Meir, A. Krakovich, T. Makmal, Soreq NRC (Israel)
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    One of the most common effects in optical fibers under exposure to ionizing radiation is degradation in transmission, commonly termed radiation induced attenuation (RIA). On one extreme, fibers with low RIA thresholds (including P-doped fibers and some plastic optical fibers) may be used as radiation sensors. On the other extreme, if one wishes to use fibers as Brillouin- or Bragg grating based temperature and strain sensors in high radiation environments, specialty fibers with very high resistance to RIA are required (radiation hardened fibers). Such fibers are often based on pure silica cores. In order to test and compare the suitability of various radiation hardened fibers we have established a test site in the 5 MW research grade reactor located at Soreq Nuclear Research Center, Israel. Several fiber samples were coiled into a specially designed apparatus which was lowered into the reactor. The input and output arms of each fiber coil were sufficiently long to remain outside the reactor and were attached to a source (input) and detector (output). The transmission/attenuation could then be measured during and in between operations of the reactor. Since the reactor does not operate continuously we were able to monitor transmissions changes under very high radiation rates (approx. 0.5 Mrad/hr) and doses (about 20 Mrad), as well as recovery processes after each reactor shut down. We will present results comparing the RIA and recovery kinetics of different commercial radiation hardened fibers under identical exposure/relaxation cycles. We will also show effects of different fiber jacket materials and a fiber with inscribed Bragg gratings.
    11773-24
    Author(s): Pasquale Imperatore, Gianluca Persichetti, Genni Testa, Romeo Bernini, Istituto per il Rilevamento Elettromagnetico dell'Ambiente (Italy)
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    In this work, we demonstrated the possibility realize a continuous measurement of liquid level based on light diffusing fibers (LDFs). The sensor consists of two parallel LDFs coupled together. The illuminating fiber is connected to a laser diode. The light scattered into the liquid is then coupled, always by the scattering, to the detection fiber and delivered to a detector. By setting a working wavelength that is strongly absorbed by the liquid, the power coupled between the fibers depends on liquid level. The sensor is made by a polymeric beam of Polyvinyl chloride (PVC), on which two LDF (3M Fibrance) with a diffusion length of 1m have been glued side by side at a distance of 1.5mm. The fiber has a core diameter of 170 μm, a low-index polymeric cladding with a diameter of 230 μm, and loose tube PVC jacket with an outer diameter of 900 μm. As light source a 1550nm fiber coupled laser diode is used. At this wavelength, water, employed as the test liquid, exhibits a strong absorption (=1210 m-1). A high sensitivity photodetector connected to a data acquisition module (DAQ) is used for measuring the detection fiber output power at different liquid levels The optical coupling phenomena between the fibers could be modelled by coupled power equations. Co-propagation and counter-propagation coupling configurations have been analyzed and experimentally validated. The measurements results are in good agreement with the theory, and demonstrate that both configurations could be used for liquid level sensing. The counter-propagation configuration exhibits a nonlinear response as function of the liquid level, while the co-propagation coupling configuration response is linear simplifying the calibration procedure. In the co-propagation configuration, the resolution ranges from ±8mm at low liquid level up to ±2mm at high liquid level over a 1m length measurement range.
    11773-25
    Author(s): Sarbojeet Bhowmick, Josef Vojtech, Lada Altmannová, Radek Velc, CESNET z.s.p.o. (Czech Republic)
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    Fibre based transmission of ultra-precise time and ultra-stable optical frequency is quickly becoming common reality, not only in the fibres used for research but also in other operational fibre networks. At the moment, a fibre represents the best precision of such transmissions. In order to achieve highest possible transmission stability up to 10-18for 1000 s averaging, the bidirectional transmission within single fibre is required including exclusive optical amplification. We present here the use and results of Optical Time Domain Reflectometry (OTDR) technique for detection of disturbances as connector losses, reflections, bending etc. on live fibres with present Amplified Spontaneous Emission (ASE) from bidirectional Erbium Doped Fibre Amplifiers (EDFAs).
    11773-26
    Author(s): Helen E. Parker, Sanghamitra Sengupta, Achar V. Harish, Ruben Soares, Håkan Jönsson, KTH Royal Institute of Technology (Sweden); Walter Margulis, RISE Acreo AB (Sweden), KTH Royal Institute of Technology (Sweden); Aman Russom, Fredrik Laurell, KTH Royal Institute of Technology (Sweden)
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    Lab-on-a-chip (LOC) microfluidics allows the miniaturization of chemical and biological processes onto a single unit. This has a well-recognized list of advantages, such as minimal sample and reagent consumption, the potential for multiplexing, rapid analysis, and portability. Often the chips are interrogated using external optics. However, silica fibers and capillaries offer interesting opportunities for more compact combination of optics and microfluidics while adding advantages typical within the fiber sensing field such as, flexibility within a high aspect ratio format, uniaxial arrangements, and measurement-at-a-distance. We present a Lab-in-a-fiber (LIF) device combining the techniques of loop-mediated isothermal amplification (LAMP), droplet microfluidics, and optofluidics to detect and quantify viral RNA. Our LIF device is constructed from a toolkit of fibers and capillaries drawn in-house and assembled using a Vytran Automated Glass Processor Workstation (GPX3000, Thorlabs). We characterize the LIF device using a dilution series of fluorescein solutions and demonstrate the device using heat-inactivated nasopharyngeal swab samples. A key feature of this design is that both fluid injection and light coupling are carried out at the same end, freeing up the length of the LIF device itself. Thus, as the techniques here are developed and modified they could find uses within a range of applications which are limited in LOC technology, such as in vivo optical interrogation of cells.
    11773-27
    Author(s): Svetlana S. Aleshkina, Tatiana Kashaykina, A. M. Prokhorov General Physics Institute (Russian Federation); Mikhail V. Yashkov, Mikhail Salganskii, G. G. Devyatykh Institute of Chemistry of High-Purity Substances (Russian Federation); Vladimir Velmiskin, Mikhail M. Bubnov, A. M. Prokhorov General Physics Institute (Russian Federation); Alexey N. Guryanov, G. G. Devyatykh Institute of Chemistry of High-Purity Substances (Russian Federation); Mikhail E. Likhachev, A. M. Prokhorov General Physics Institute (Russian Federation)
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    Here for the first time the technique of the resonant modes coupling is used for spectrally-selective fundamental mode suppression. In our work we considered the fiber design consisting of the low-index core surrounding by the appropriately chosen high-index absorbing rods. Mode suppression in this case happens due to the resonant core mode deformation owing to mode-anticrossing effect and its partial absorption into the rods. According to our calculations it was established that stop-band of the core fundamental mode can be easily adjusted for different practical aims by fiber bending. Furthermore, in the present work we implemented and studied passive fiber with three high-index absorbing rods incorporated into fiber cladding. The Sm was chosen as an absorbing element of the high-index rods.
    11773-28
    Author(s): Kinga Zolnacz, Mateusz Szatkowski, Jan Masajada, Waclaw Urbanczyk, Wroclaw Univ. of Science and Technology (Poland)
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    We report a white-light interferometric method for broad-band measurements of chromatic dispersion of higher-order-modes (HOMs) selectively excited in an optical fiber using a spatial light modulator (SLM). To excite a specific mode we appropriately modulated a phase distribution across a supercontinuum input beam with the SLM used in reflective configuration. For this purpose, the SLM surface was divided into azimuthally and radially distributed sectors which introduce the phase shifts equal alternately to 0 or π radians, similarly as in the targeted mode. The voltage applied to respective sectors of the SLM was corrected versus wavelength to ensure broad-band dispersion measurements for the required mode. For a given voltage setting, the dispersion measurements were possible without any correction over 250 nm in the visible and over even greater range in the infrared. We demonstrate feasibility of the proposed approach in the measurements of chromatic dispersion for all modes supported by Corning SMF-28e, i.e., LP01, LP11, LP21, LP02, and LP31. The measurements were conducted in the spectral range from 450 nm up to the cut-off wavelengths of respective higher order modes and up to 1600 nm for the fundamental mode.
    Session 6: Optical Fiber Metrology and Polymer Optical Fibers
    11773-29
    Author(s): Bar Gelkop, Linoy Aichnboim, Dror Malka, Holon Institute of Technology (Israel)
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    The foundation of wavelength division multiplexing (WDM) lies in the ability to send different data types over waveguide networks in the form of light. Recently, visible light communication (VLC) has become more popular due to the rise of wireless data communication in the world. However, the main challenges of using the VLC system are the high path loss due to the reasonably high frequency and to obtain a high data communication bit rate. The solution to overcoming these problems is to use a very low loss WDM technology such as polymer optical fiber (POF). One of the common methods for achieving a higher data bitrate using the VLC fibers system is to use wavelength division multiplexing. However, the implementation of WDM for RGB signals requires additional devices that can limit the system performances. To solve this issue, we introduce a new study for designing an RGB multiplexer based on multicore polymer optical fiber (MC-POF). The new structure is based on replacing seven air-holes regions with polycarbonate (PC) cores over the fiber length. Each PC core size was designed to be suitable to the light coupling of the operating wavelengths which allows us to control the light switching between closer PC cores and to obtain an RGB multiplexer device without adding more devices. The locations and the sizes of the PC cores over the fiber length and the geometrical parameters pitch and diameter of the MC-POF were studied and optimized using the beam propagation method (BPM). Results show that after a 20 mm light propagation the PC MC-POF RGB multiplexer can be obtained with a low power loss of 0.6 to 1.02 dB, large bandwidth of 7.3 to 28.4 nm, and good isolation between the transmission of the input R/G/B wavelengths. This can lead to a very compact WDM-VLC system with a better power consumption performance that can be utilized to transmitted high-speed RGB signals over POF.
    11773-30
    Author(s): Meriem Benlacheheb, Lynda Cherbi-Bazi, Nedjmeddine Ammar Merabet, Univ. des Sciences et de la Technologie Houari Boumediene (Algeria)
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    A highly birefringent polymer photonic crystal fiber (PCF) for polarization maintaining is investigated in this work. A triangular structure of circular air-hole included in polytherimide polymer (PEI) with a defected core for high birefringence is modeled. The properties of this structure are simulated using a full vector finite element method (FVFEM) using a boundary condition made of polysilicon material. The optimized design ensures a very high birefringence of 4.9 x 10-2 at a wavelength of 1550 nm. Furthermore, we have achieved an extremely low confinement loss around 10-6 dB/km and negative chromatic dispersion of -180.8 ps/nm/km along the y polarization. Owing to the excellent polarization maintaining properties, the proposed fiber design could be easily suitable for optical sensors applications. The proposed structure could also enhance the dispersion compensating devices in high bite rate transmission network due to its high normal dispersion especially for the obtained high birefringence which prevents the main issue of the random power coupling between the two polarization modes.
    11773-31
    Author(s): Christian-Alexander Bunge, Hochschule für Technik, Wirtschaft und Kultur Leipzig (Germany); Jan Kallweit, Thomas Vad, Institut für Textiltechnik der RWTH Aachen University (Germany); Thore Koritzius, Hochschule für Technik (Germany); Thomas Gries, Institut für Textiltechnik der RWTH Aachen University (Germany)
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    The structural properties of PMMA, which has been melt-spun and treated using a specific cooling profile, is investigated in order to evoke desired optical and mechanical properties. Several PMMA fibres, which had been melt spun and subsequently processed with different temperature profiles, were analysed by small-angle X-ray scattering (SAXS) measurements.1 These results will be compared to a combination of numerical models, which consider the quenching of a filamentary PMMA polymer melt in water.2 This multi-scale simulation considers macroscopically the cooling process in the water and within the fiber. The spatially resolved cooling rates, which have been simulated at different locations serve as input for a 3D-Monte-Carlo polymer simulation model, which takes, among others, the Lennard-Jones, the bending and bond potentials into account in order to predict the resulting PMMA structure of the fabricated fiber.
    11773-32
    Author(s): Yonggang Huang, China Building Materials Academy (China); kaichao Zhou, North Vision Technology Co., Ltd. (China); Peng Jiao, Weijie Hou, Yun Wang, Yang Fu, cbma (China); You Zhou, Jiuwang Wang, CBMA (China)
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    With the development of LLL night vision technology from the second and third generation to 4G, the specifications of imaging have been significantly improved. In particular, the contrast of imaging, which determines the clarity, even resolution of the image. The contrast of imaging also refers to the Stray Light Crosstalk (SLC) among optical fibers. How to characterize the contrast of Optical Fiber Imaging Elements (OFIE) by detecting the SLC has become an important problem that must be solved. At present, the contrast performance is often characterized by the Knife-edge Response Value (KERV), which is the transmittance value of light passing through the knife edge through optical fiber imaging element. However, KRV has some disadvantages, such as inaccurate measurement value, harsh test conditions, complex sample preparation and great influence on the measurement result. The most important disadvantage is that KRV is an indirect detection, which needs to slice and grind the tested sample, and the slice position often cannot represent the overall contrast performance of the tested OFIE. In this paper, the digital imaging equipment (high-precision CMOS camera + high-resolution microscope) is used to take photo of the end face of the OPIE placed on the black-and-white boundary of the USAF resolution target. The process of light passing through the black-and-white edge provides accurate information for the contrast change. Through the computer analysis and processing of the digital image, the SLC in different positions of the OPIEs is obtained. The SLC can be used to analyze the degree of crosstalk, or contrast. The digital imaging equipment mainly includes light source system, precision transmission system, CCD camera system, software analysis system and control system. The equipment has the advantages of direct detection, simple operation, high precision, good repeatability and reliability, convenient maintenance, and can be used to test and analyze the imaging contrast of all optical fiber imaging elements. It has been proved that the device is effective in detecting the SLC, and completely replaces the KRV method. Key words: Optical fiber imaging elements, Optical fiber, Stray light crosstalk (SLC), Contrast, Detection device
    11773-34
    Author(s): Yazhou Wang, Abubakar I. Adamu, Technical Univ. of Denmark (Denmark); Rodrigo Amezcua Correa, Univ. of Central Florida (United States); Ole Bang, Christos Markos, Technical Univ. of Denmark (Denmark)
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    We report a high-precision and repeatable micro-machining technique using focused ion beam (FIB) milling on a nodeless ARHCF. Ga+ ions are bombarded on a 43 µm thick outer cladding of ARHCF for 30 minutes, to create a 50 µm deep fluidic channel. The micro-channel in the silica cladding is precisely drilled at the middle position of two adjacent capillaries with a 2.8 µm gap, providing direct access for liquid/gas to diffuse into the hollow-core region, but also avoiding the damage of the capillaries. Corroborating results from simulation of such a structure are presented to demonstrate that no additional loss is induced by the milled structure. This method indicates that an all-fiber structure for optofluidic applications can be achieved by splicing nodeless ARHCF with solid-core fibers, while preserving the fluidic channels without compromising the low-loss performance of ARHCF.
    Session PS: Poster Session
    11773-35
    Author(s): Norbert Tarjányi, Daniel Kacik, Univ. of Žilina (Slovakia); Raphael Jamier, Georges Humbert, Philippe Roy, Jean-Louis Auguste, XLIM (France)
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    Birefringent optical fibers are widely used in many applications requiring that the output state of polarization must remain unchanged or, at least, well under the control. If the birefringence of the fiber is affected by any external physical quantity such as temperature, atmospheric pressure, force, etc., and still being well under control, the fiber can be used as a sensor of that quantity. The effect of the change of the external conditions on the birefringence of the fiber can be observed by the change of polarization state of the wave at the output of the fiber. Most simply, this change is manifested by a change of intensity of light when an appropriate polarizing element is placed behind the fiber end. Since the fiber, in general, can be used with any source of light, it is important to possess knowledge on the birefringence dispersion in as wide wavelength range as possible. Moreover, in the case of an application utilizing the broadband source of light we have to distinguish between phase and group birefringence of the fiber, as well. In the paper, we focus on both the experimental and the theoretical investigations leading to the determination of the group and phase birefringence of the fabricated Hi-Bi fiber using a broadband light source. The measurement is performed for fiber samples with various lengths. Several approaches for determination of the group and phase birefringence of the investigated fiber are discussed and experimentally performed, and the results are compared.
    11773-36
    Author(s): Petr Varak, Jan Mrazek, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic); Wilfried Blanc, Institut de Physique de Nice (France); Jan Aubrecht, Michal Kamradek, Ondrej Podrazky, Pavel Honzátko, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic)
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    Thulium- and holmium-doped fiber lasers operating in the “eye-safe” 2 µm region receive growing attention for their potential in applications such as laser surgery, biological imaging, atmospheric sensing or material processing. Amongst materials for the fabrication of rare-earth-doped fibers, silica glass remains popular thanks to numerous advantages such as high transparency up to NIR region, good thermal or chemical stability and high durability. However, several drawbacks put silica glass in disadvantage compared to soft glass systems such as telluride or fluoride glass. Limited solubility of rare-earth ions in silica glass leads to the formation of clusters which causes concentration quenching and hinders luminescence properties. Silica glass also has a high phonon energy (≈1100 cm-1) which increases the probability of non-radiative transitions and further limits radiative properties. To overcome these shortcomings, silica glass needs to be modified with other oxides. Zirconium oxide (ZrO2) is a perspective co-dopant of rare-earth ions in silica glass. With an appropriate heat treatment, a phase separation occurs in the SiO2-ZrO2 system which leads to the formation of ZrO2 nanoparticles. The nanoparticles prevent the clustering of rare-earth ions and improve luminescence properties. ZrO2 particles also possess low phonon energy (≈470 cm-1) which increases the number and probability of radiative transitions of rare-earth ions. Furthermore, a good optical transparency, chemical durability and high refractive index make ZrO2 a suitable candidate for the fabrication of rare-earth doped optical fibers. In this contribution, we report on the experimental preparation and characterization of holmium- and thulium-doped ZrO2-SiO2 fibers for use in fiber lasers. The optimal concentrations of rare-earth ions and ZrO2 in silica fibers were investigated, and the fibers were characterized in regards to their photoluminescence properties (emission spectra, fluorescence lifetimes). The fibers were tested in a fiber laser setup and their laser characteristics were evaluated.
    11773-37
    Author(s): Shovasis Kumar Biswas, Independent Univ., Bangladesh (Bangladesh); Rishad Arfin, Zunayeed Bin Zahir, Ashfia Binte Habib, Riasat Khan, Mohammad Rezaul Islam, Syed Athar Bin Amir, North South Univ. (Bangladesh); Arif Ul Alam, McMaster Univ. (Canada)
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    Photonic crystal fibers (PCFs) are microstructure optical fibers, which demonstrate unique optical properties by exploiting the guiding mechanism of electromagnetic waves through the periodic formation of refractive indices. PCF with high negative dispersion and enhanced nonlinearity is often desirable for improving the signal quality in long-haul light-wave communication and different nonlinear optical applications. Investigations have been carried out previously on dispersion and nonlinearity for several numerical designs of PCF through the variation of structural parameters. However, the designs of photonic fibers, which are comprised of noncircular air holes are difficult and challenging to fabricate with existing technologies. In this work, an analytical design of hexagonal photonic crystal fiber (H-PCF), which consists of all circular air holes is proposed. The primary aim of the proposed numerical design is to attain desired optical characteristics by using circular air holes only to make the fiber simple and feasible for standard fabrication process. The proposed H-PCF consists of a regular hexagonal lattice structure, where the size and location of the few air holes are changed in order to obtain high optical dispersion and enhanced nonlinearity. The corresponding modal properties resulting from geometrical modification and the optimal values of the geometrical parameters are investigated using the numerical electromagnetic solver based on finite element method (FEM). The numerical results show that our proposed H-PCF achieves a large dispersion of −2304 ps/(nm.km) and nonlinearity of 110.8 W^(-1)km^(-1) at the operating wavelength of 1.55 µm. The proposed structure offers design flexibility since only circular air holes are involved in the design. Our proposed H-PCF structure can be considered to be a prospective candidate for dispersion compensation in long-haul optical communication and several other applications such as optical modulation and amplification.
    11773-39
    Author(s): Ondřej Schreiber, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic), Czech Technical Univ. in Prague (Czech Republic); Jan Aubrecht, Ali Jasim, Filip Todorov, Pavel Honzátko, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic)
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    Thulium-doped fiber lasers (TDFLs) have been extensively investigated as the most promising source of efficient laser emission at wavelengths around 2 um, i. e., in the eye-safer spectral region and in the atmospheric window as well. It allows for wide range of applications including medicine, defense, distance measurement or materials processing. To enhance pump absorption effectivity along the active double-clad (DC) fiber, good overlap of the pump light and doped fiber core should be achieved along the fiber length. The overlap can be increased by breaking the circular symmetry of the inner cladding by shaping its cross-section, e. g., into a polygon or D-shape. Recently, additional twisting of active fibers with non-circular cross-section has been proposed to further advance absorption effectivity. In this work we present experimental measurement of 792 nm pump cladding absorbance of a series of double-clad active thulium-doped fibers with respect to their bend radius, the inner cladding cross-sectional shape and twist rate. With these fibers, we assembled a set of thulium-doped fiber lasers with different resonator setups and tested their performance. Twisting was introduced to fiber during drawing from an octagonal, CO2 laser-shaped preform so that the twist remained frozen in the drawn fiber. We have shown that the fiber twist significantly improves the pump absorption even in the case of straight or coiled fibers with large coil radii. Optimal diameter coiling of both circular and non-twisted octagonal active fiber induces substantial increase in absorption efficiency. We provide a comparison of several pumping and resonator schemes. These new concepts including preform spinning shall result in highly efficient lasers of a small footprint and reduced need for cooling that shall have a great potential for applications where low power consumption, tightly limited space, and low weight are required.
    11773-40
    Author(s): Daniel Dousek, Czech Technical Univ. in Prague (Czech Republic); Matěj Komanec, Ailing Zhong, Dmytro Suslov, Stanislav Zvánovec, Petr Vesely, Czech Technical Univ. in Prague (Czech Republic); Yong Chen, Thomas D. Bradley, Eric R. Numkam Fokoua, Francesco Poletti, David J. Richardson, Radan Slavík, Optoelectronics Research Ctr. (United Kingdom)
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    Hollow-core optical fibers (HCFs) offer significant advantages over standard glass-core single-mode fibers (SSMFs) such as low nonlinearity, ability to transmit high powers, and low loss even in spectral regions where silica glass suffers from relatively high loss (e.g., in the mid-infrared). Furthermore, HCFs were recently reported with a loss below that of SSMF at wavelengths below 800 nm. Even in the lowest-loss SSMF window of 1550-nm, HCF attenuation is getting close to that of SSMF (currently as low as 0.28 dB/km for HCF). To fully exploit their potential, HCFs need to be integrated into SSMF based systems. Recently, we presented a new HCF-SSMF interconnection technique, which is based on gluing. Unlike the popular fusion splicing, it allows an anti-reflective coating to be applied at the interface, which suppresses the 4% Fresnel back-reflection that otherwise occurs at the interface between the glass core of SSMF and the hollow core of HCF. Although fiber gluing is well-established in telecoms (e.g., to pigtail modulators or planar lightwave circuit large-port couplers), it is a new technique for joining to HCFs that have a central hole surrounded by microstructure (into which the glue or its vapors may penetrate). Here, we present a study in to the long-term stability of glued, low loss (<0.55 dB) HCF-SSMF interconnections (for HCF with a 19-cell photonic bandgap geometry). Firstly, we measured the loss of 3 samples over a period of 100 days at room temperature, observing a variation in insertion loss of less than 0.04 dB. Subsequently, we placed the samples into a climatic chamber and heated them up to +85°C. A maximum insertion loss variation of 0.1 dB was observed during 4 full thermal cycles. At the conference, we will present a comprehensive set of results and discuss how the small degradations observed might be further reduced/eliminated.
    11773-41
    Author(s): Martin Grábner, Pavel Peterka, Pavel Honzátko, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic)
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    The high power optical fibers with a doped active core are subject to heating due to non-radiative absorption of pumping power in the core area. The heat generated in the central part of a fiber is conducted to its outer parts resulting in temperature distribution on the fiber cross section. Efficient cooling is needed in order to avoid thermal damage of the fiber, in particular on the boundary between silica cladding and fiber coating. Temperature distribution in the fiber and its surrounding can be estimated by solving a steady-state heat conduction problem in a domain of fiber cross-section characterized by different values of thermal conductivity of different materials present. In this work, the problem is solved numerically by a finite element method for several kinds of fiber cross sections including a fiber with an octagonal cladding structure. It is shown that the temperature on the critical boundary cladding-coating is increasing linearly with the heat load with the slope determined by the boundary radius. The effect of different shapes of metal slot guiding the fiber is demonstrated.
    11773-42
    Author(s): Jan Pokorný, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic), Czech Technical Univ. in Prague (Czech Republic); Ondřej Moravec, Jan Aubrecht, Institute of Photonics and Electronics of the CAS, v.v.i. (Czech Republic)
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    We report on experimental setup and characterization of a broadband fiber-optic thulium-doped source of amplified spontaneous emission (ASE), which generates radiation in a spectral region around 2 micrometer wavelengths. We review the current state of the art in the field of broadband optical sources in this wavelength range and point out advantages of Tm fiber ASE sources namely the stability and high optical power spectral density compared to other available sources. We present a broadband source based on core-pumped thulium-doped fiber fabricated in house using the modified chemical vapor deposition method, pumped by erbium-doped fiber laser at 1566 nm. The ASE source in a backward configuration with respect to the pump operates in a single-ended configuration achieved using a simple all-fiber geometry and produces radiation with an output power of up to 350 mW. The output spectrum is combined from two local ASE peaks of the Tm-doped fiber, at around 1840 nm and at around 1930 nm, with total 3-dB width of more than 140 nm and output power of 130 mW.
    11773-43
    Author(s): Qiming He, Aojie Zhao, Bo Li, Jinhong Zhang, Jiahui Liu, Xianlin Song, Nanchang University (China)
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    Through the photoacoustic imaging model based on compression perception theory built by k-wave toolbox, the image is reconstructed with Hadama observation matrix and StOMP algorithm. The reconstructed image contains the main information of the original image. This indicates that the original image can be reconstructed by compression perception theory and appropriate denoising method. Compared with Nyquist's sampling method, compression perception theory greatly reduces the amount of data collected. It saves resources and space to a great extent and has great advantages for big data photoacoustic imaging. It can also provide time convenience for subsequent image analysis.
    Conference Chair
    Cyprus Univ. of Technology (Cyprus)
    Conference Chair
    MCH Engineering LLC (United States)
    Conference Chair
    Institute of Photonics and Electronics of the ASCR, v.v.i. (Czech Republic)
    Program Committee
    Univ. de Rennes 1 (France)
    Program Committee
    Clemson Univ. (United States)
    Program Committee
    DTU Fotonik (Denmark)
    Program Committee
    Institut für Photonische Technologien e.V. (Germany)
    Program Committee
    Neil G. R. Broderick
    The Univ. of Auckland (New Zealand)
    Program Committee
    The Univ. of Sydney (Australia)
    Program Committee
    Christopher Emslie
    Fibercore Ltd. (United Kingdom)
    Program Committee
    XLIM Institut de Recherche (France)
    Program Committee
    Technische Hochschule Mittelhessen (Germany)
    Program Committee
    Univ. of Bath (United Kingdom)
    Program Committee
    Frederick Univ. (Cyprus)
    Program Committee
    Aalto Univ. School of Science and Technology (Finland)
    Program Committee
    Walter Margulis
    Acreo Swedish ICT AB (Sweden)
    Program Committee
    Fibercore Ltd. (United Kingdom)
    Program Committee
    Valerio Romano
    Berner Fachhochschule Technik und Informatik (Switzerland)
    Program Committee
    Institut für Photonische Technologien e.V. (Germany)
    Program Committee
    Wroclaw Univ. of Technology (Poland)
    Program Committee
    Aston Univ. (United Kingdom)
    Program Committee
    Alexei M. Zheltikov
    Lomonosov Moscow State Univ. (Russian Federation)
    Additional Information
    Optical Fiber Lab virtual Tour
    The Institute of Photonics and Electronics of the CAS offers an opportunity to explore the laboratory for fabrication of specialty optical fibres via a virtual tour as part of the Optical Fiber Technology Industry Sessions and the Conference on Micro-structured and Specialty Optical Fibres.
    Please follow the link below to find out more about the lab facilities:
    https://www.ufe.cz/en/spie-2021-virtual-optical-fiber-lab-guided-tour