Suspended-core Fiber Research Articles

Structure design and numerical evaluation of highly nonlinear suspended-core chalcogenide fibers

Chalcogenide suspended core fibers are considered as an excellent candidates for several applications in near-and-mid IR applications because of their characteristics of higher linearity and nonlinearity. In this paper, the influence of the fiber structure and host glass on dispersion and nonlinear properties, including the core size and the width of the bridge, especially the shape of the fiber core were analyzed with the finite element method in detail. And then, the optimized structure of SCFs made of As2S3, Ge20Sb5Se75, As2Se3, Ge15As15Se17Te5, which stand for the typical samples of S-based, Se-based and Te-based chalcogenide glasses, have been adopted to get suitable dispersion properties and highest nonlinear optical properties in all kinds of glasses.

Enhancement of evanescent field exposure in a photonic crystal fibre with interstitial holes

In this work, a modified photonic crystal fibre (PCF) that we refer to as Sunny PCF with enhanced evanescent field exposure structure is proposed. The Sunny PCF with triangular interstitial air holes surrounding the core region increases the interaction of the guided mode with the air. Full-vectorial finite element method with perfectly matched layer boundary condition is used to design and simulate the sensitivity and confinement loss characteristics of the proposed Sunny PCF. By adding sunny structure to a conventional PCF with air-filling ratio of 0.9, the highest achievable sensitivity with negligible confinement loss can be boosted up to 21.23% from 15.83% at the operating wavelength of 1550 nm. Sunny PCF can achieve the same sensitivity as suspended-core holey fibre with lower confinement loss. A preliminary Sunny PCF has been fabricated to prove the feasibility of the proposed structure.

Mid-infrared supercontinuum generation in a three-hole Ge 20 Sb 15 Se 65 chalcogenide suspended-core fiber

Abstract This work experimentally demonstrates the supercontinuum (SC) generation in a three-hole arsenic free Ge 20 Sb 15 Se 65 chalcogenide suspended-core fiber. Mechanical drilling was used to prepare the chalcogenide glass preform, which was drawn into suspended-core fibers. The zero-dispersion wavelength of the fiber is moved toward the shorter wavelength of about 3.2 μm through changing the fiber core diameter by controlling the pressure of inert gas during fiber drawing. When a 15 cm-long fiber with a core diameter of 6 μm is pumped using 150 fs pulses at 3.3 μm, SC spanning from ∼3 μm to ∼8 μm was generated.

Electrically Tunable Multiwavelength Bragg Grating Filter Acoustically Induced in a Highly Birefringent Suspended Core Fiber

Multiwavelength reflection spectra induced by an acoustically modulated fiber Bragg grating (FBG) in a highly birefringent suspended core fiber are experimentally investigated. Longitudinal acoustic waves interacting with a grating generate side lobes in the reflectivity spectrum and produce a superposed reflection band. The reflectivity of up to five wavelength peaks can be actively tuned by the voltage of the electrical signal inducing the acoustic waves. This indicates new possibilities for compact and fast multiwavelength dynamic and fiber-integrated reflection filters.

Terahertz circular fiber polarizers using suspended-core spiral fibers.

A terahertz (THz) fiber circular polarizer based on suspended core fibers is proposed and analyzed. The THz mode guides within a subwavelength-scale core, which is suspended in a polymer tube. The dry air inner cladding not only suppresses the absorption loss of the device but also supports the leaky cladding modes. The circularly polarized core mode with the same handedness of the grating couples to the leaky cladding modes suffers from loss near resonant frequencies due to the spiral structure of the fiber. The principles and characteristics of the proposed circular polarizer are theoretically derived. Parameters that have influence on the performances are analyzed by numerical simulations. Simulation results show that the proposed THz fiber polarizer exhibits a broad single circular polarization bandwidth and a relatively low absorption loss.

Nanoparticle functionalised small-core suspended-core fibre - a novel platform for efficient sensing.

Detecting small quantities of specific target molecules is of major importance within bioanalytics for efficient disease diagnostics. One promising sensing approach relies on combining plasmonically-active waveguides with microfluidics yielding an easy-to-use sensing platform. Here we introduce suspended-core fibres containing immobilised plasmonic nanoparticles surrounding the guiding core as a concept for an entirely integrated optofluidic platform for efficient refractive index sensing. Due to the extremely small optical core and the large adjacent microfluidic channels, over two orders of magnitude of nanoparticle coverage densities have been accessed with millimetre-long sample lengths showing refractive index sensitivities of 170 nm/RIU for aqueous analytes where the fibre interior is functionalised by gold nanospheres. Our concept represents a fully integrated optofluidic sensing system demanding small sample volumes and allowing for real-time analyte monitoring, both of which are highly relevant within invasive bioanalytics, particularly within molecular disease diagnostics and environmental science.

Simulation Study on Dispersion Properties of As2S3Three-Bridge Suspended-Core Fiber

In this paper, the chromatic dispersion of the As2S3 three-bridge suspended-core fiber (SCF) is numerically investigated. All the cross-section parameters, including the thickness of the bridges and the internal circle and external circle diameter of the air hole, have been considering in the simulation of the SCFs by means of the full-vectorial finite-element method in detail. Eighty three models with different structural parameters are established, and the changes of the chromatic dispersion and zero-dispersion wavelength (ZDW) of the fundamental mode in the wavelength ranging from 0.6 to 11.6 $\mu \text{m}$ are evaluated. The relations between the dispersion and structural parameters are obtained by numerical simulations. Numerical results indicate that a proper design of the bridges and air holes can significantly change the dispersion properties of the SCF. A SCF with dual-ZDW (1.805 & 5.315 $\mu \text{m}$ ), highly nonlinearity (3.480683 $\text{m}^{-1}\text{W}^{-1}$ ), and flattened chromatic dispersion ( $\text {km}\cdot \text {nm}$ )), which can be used to generate broadband supercontinuum, is obtained by optimizing the structural parameters.

Interferometric temperature sensor based on a water-filled suspended-core fiber

Abstract The performance of water-filled suspended-core fibers as key components of interferometric temperature sensors has been analyzed. Use of water is motivated by simplicity of use and by its thermo-optic and thermal expansion coefficients, which provide a good balance between sensitivity and wide temperature range (limited by the free spectral range of the interferometer). Two suspended core fibers have been tested. With one of them, the sensitivity observed is slightly better than the ones of most interferometers based on liquid-filled photonic crystal fibers, with a linear temperature range of 25 °C. With regard to the other one, its most remarkable feature is its temperature range, not limited by any interferometric property but by water melting and boiling temperatures, as its quotient between free spectral range and sensitivity is higher than 100 °C.

Suspended Core Fibers for the Transmission of Cylindrical Vector Modes

This paper presents a study of propagation of radially and azimuthally polarized cylindrical vector modes in six-strut suspended core fibers based on finite element simulations. The study shows that large effective index differences in the order of $10^{-3}- 10^{-2}$ of these modes can be achieved in the suspended core fibers with core diameter of less than 2 μ m, material index 1.45 of silica to 2.0 of tellurite, and wavelength of 750 nm, allowing the stable propagation of the first higher order modes in doughnut shape within these fibers. The effective index difference and the field intensity of these cylindrical vector modes can be tuned by selecting appropriate fiber material and core size. The study shows that the suspended core fiber can be a competitive candidate for fiber-based high-resolution stimulated emission depletion nanoscopy application.

Temperature dependence of birefringence in ethanol-filled suspended core fiber.

The temperature dependence of the birefringence in a suspended core fiber (SCF) has been experimentally analyzed by using a polarimetric setup. The used configuration consists of two linear polarizers and the SCF as birefringent medium. A theoretical study based on Jones matrices has been carried out to analyze the experimental observed behavior. For this, a polarimetric all-fiber configuration was used whose sensitivity depends on the wavelength variation with temperature. Results obtained show that it is strongly affected when the air holes of SCF are partially filled with ethanol.

Quantification of the fluorescence sensing performance of microstructured optical fibers compared to multi-mode fiber tips.

Microstructured optical fibers, particularly those with a suspended-core geometry, have frequently been argued as efficient evanescent-field fluorescence-based sensors. However, to date there has not been a systematic comparison between such fibers and the more common geometry of a multi-mode fiber tip sensor. In this paper we make a direct comparison between these two fiber sensor geometries both theoretically and experimentally. Our results confirm that suspended-core fibers provide a significant advantage in terms of total collected fluorescence signal compared to multi-mode fibers using an equivalent experimental configuration.

Supercontinuum generation in three-fold symmetry microstructured fibers in visible and infrared spectral regions

We present a series of three fold symmetric silica microstructured fibers for nonlinear application. The fibers are designed to have zero dispersion wavelength far from the pump wavelength. In our fibers a domination of nonlinear effects is precisely controlled by selectively increased three air holes in the vicinity of the core. Our fibers allow for the broadband single mode spectrum generation and the achievement of flat spectra even after changes of fiber dispersion caused by fabrication inaccuracies. Full Text: PDF References S. T. S?rensen, C. Larsen, C. Jakobsen, C. L. Thomsen, and O. Bang, "Single-mode pumped high air-fill fraction photonic crystal fiber taper for high-power deep-blue supercontinuum sources", Opt. Lett, 39, 1097 (2014). CrossRef V. Couderc, P. Leproux, V. Tombelaine, L. Grossard, and A. Barthélémy, "Raman cascade suppression by using wide band parametric conversion in large normal dispersion regime", Opt. Express, 13, 8584 (2005). CrossRef H. E. Heidepriem, S. C. W. Smith, and T. M. Monro, "Suspended nanowires: Fabrication, design and characterization of fibers with nanoscale cores", Opt. Express, 17, 2646 (2009). CrossRef U. M?ller, Y. Yu, I. Kubat, C. R. Petersen, X. Gai, L. Brilland, D. M´echin, C. Caillaud, J. Troles, B. Davies, and O. Bang, "Multi-milliwatt mid-infrared supercontinuum generation in a suspended core chalcogenide fiber", Opt. Express, 17, 3282 (2015). CrossRef I. Shavrin, S. Novotny, and H. Ludvigsen, "Mode excitation and supercontinuum generation in a few-mode suspended-core fiber", Opt. Express, 21, 32141 (2013). CrossRef M. Klimczak, G. Stepniewski, H. Bookey, A. Szolno, R. Stepien, D. Pysz, A. Kar, A. Waddie, M. R. Taghizadeh, and R. Buczynski, "Broadband infrared supercontinuum generation in hexagonal-lattice tellurite photonic crystal fiber with dispersion optimized for pumping near 1560??nm: reply", Opt. Lett. 39, 2241 (2014). CrossRef X. Zhang, X. Zhu, X. Chen, H. Li, J. Peng, N. Dai, and J. Li, "A hollow beam supercontinuum generation by the supermode superposition in a GeO2 doped triangular-core photonic crystal fiber", Opt. Express, 20, 19799 (2012). CrossRef C. Lesvigne, V. Couderc, A. Tonello, P. Leproux, A. Barthélémy, S. Lacroix, F. Druon, P. Blandin, M. Hanna, and P. Georges, "Visible supercontinuum generation controlled by intermodal four-wave mixing in microstructured fiber", Opt. Lett, 32, 2173 (2007). CrossRef S. T. S?rensen, U. M?ller, C. Larsen, P. M. Moselund, C. Jakobsen, J. Johansen, T. V. Andersen, C. L. Thomsen, and O. Bang, "Deep-blue supercontinnum sources with optimum taper profiles ? verification of GAM", Opt. Express, 20, 10635 (2012). CrossRef A. Kudlinski, M. Lelek, B. Barviau, L. Audry, and A. Mussot, "Efficient blue conversion from a 1064 nm microchip laser in long photonic crystal fiber tapers for fluorescence microscopy", Opt. Express, 18, 16640 (2010). CrossRef A. Kudlinski, G. Bouwmans, O. Vanvincq, Y. Quiquempois, A. Le Rouge, L. Bigot, G. Mélin, and A. Mussot, "White-light cw-pumped supercontinuum generation in highly GeO2 -doped-core photonic crystal fibers", Opt. Lett. 34, 3631 (2009). CrossRef A. Kudlinski, V. Pureur, G. Bouwmans, and A. Mussot, "Experimental investigation of combined four-wave mixing and Raman effect in the normal dispersion regime of a photonic crystal fiber", Opt. Lett. 33, 2488 (2008). CrossRef Z. Holdynski, M. Napierala, P. Mergo, and T. Nasilowski, "Experimental Investigation of Supercontinuum Generation in Photonic Crystal Fibers Pumped With Sub-ns Pulses", J. Lightwave Technol., 33, 2106 (2015). CrossRef U. M?ller, S. T. S?rensen, C. Larsen, P. M. Moselund, C. Jakobsen ,J. Johansen, C. L. Thomsen, O. Bang, "Optimum PCF tapers for blue-enhanced supercontinuum sources", Opt. Fiber Technol., 18, 3104 (2012). CrossRef

Compact supercontinuum sources based on tellurite suspended core fibers for absorption spectroscopy beyond 2 μm

We present the experimental development of two compact supercontinuum laser sources based on tellurite suspended core fibers with and without tapering post-processing. The pumping scheme makes use of commercially-available nJ-level femtosecond and picosecond fiber lasers at 1.56 and 2.06 μm respectively. The resulting spectral broadening that occurs in a few tens-of-centimeters of tellurite fiber allows coverage of the convenient molecular fingerprint region between 2 and 3 μm. It is then exploited in a proof-of-principle experiment for methane spectroscopy measurements in the mid-infrared by means of the supercontinuum absorption spectroscopy technique. Experimental results are in fairly good agreement with both numerical simulations of supercontinuum generation and spectroscopic predictions of the HITRAN database.

Experimental long-term survey of mid-infrared supercontinuum source based on As2S3 suspended-core fibers

The evolution of supercontinuum generation in chalcogenide suspended-core microstructured optical fibers is studied with regard to their exposure to the room atmosphere. We report the experimental proof of aging-induced supercontinuum generation drift in chalcogenide microstructured fibers. Mid-infrared supercontinuum covering the 2.5–5.5-µm spectral region is demonstrated in a fresh and 7-month-aged counterpart As2S3 fibers, by means of a home-built multistage oscillator power amplifier delivering 300 fs pulses at a repetition rate of 43 MHz in the 3.0–4.1-µm range. Numerical simulations based on the generalized nonlinear Schrodinger equation confirm the significant alteration of supercontinuum generation due to increasing fundamental OH and SH absorption bands.

Integration of conductive reduced graphene oxide into microstructured optical fibres for optoelectronics applications.

Integration of conductive materials into optical fibres can largely expand functions of fibre devices including surface plasmon resonator/metamaterial, modulators/detectors, or biosensors. Some early attempts have been made to incorporate metals such as tin into fibres during the fibre drawing process. Due to the restricted range of materials that have compatible melting temperatures with that of silica glass, the methods to incorporate metals along the length of the fibres are very challenging. Moreover, metals are nontransparent with strong light absorption, which causes high fibre loss. This article demonstrates a novel but simple method for creating transparent conductive reduced graphene oxide film onto microstructured silica fibres for potential optoelectronic applications. The strongly confined evanescent field of the suspended core fibres with only 2 μW average power was creatively used to transform graphene oxide into reduced graphene oxide with negligible additional loss. Existence of reduced graphene oxide was confirmed by their characteristic Raman signals, shifting of their fluorescence peaks as well as largely decreased resistance of the bulk GO film after laser beam exposure.

Temperature sensing up to 1300°C using suspended-core microstructured optical fibers.

We demonstrate a new approach to high temperature sensing using femtosecond laser ablation gratings within silica suspended-core microstructured optical fibers. The simple geometry of the suspended-core fiber allows for femtosecond laser processing directly through the fiber cladding. Pure silica glass is used, allowing the sensor to be used up to temperatures as high as 1300°C while still allowing the fibre to be spliced to conventional fiber. The sensor can also be wavelength division multiplexed, with three sensors in a single fiber demonstrated.

Strain-independent high-temperature sensor with a suspended-core fiber based Mach–Zehnder interferometer

Abstract A simple Mach–Zehnder interferometer (MZI) was presented for high temperature measurement. The device was composed of a short segment of suspended-core fiber (SCF) sandwiched between two standard single mode fibers (SMFs) with a misaligned splicing joint. Lower temperature measurements were firstly carried out from room temperature to 190 °C, and the obtained sensitivity at the wavelength of 1465 nm was 25.82 pm/°C. However, a nonlinear response was further achieved for high-temperature sensing up to 1000 °C. Between 20 and 200 °C, the sensitivity was just 24.24 pm/°C at the wavelength of 1457 nm, whereas a higher sensitivity of 53.87 pm/°C was acquired in the range of 200–1000 °C. In addition, the strain cross-sensitivity was extremely low. As a result, the device can be developed as a strain-independent temperature sensor and become an excellent candidate for high temperature measurement.

Broadband mid-infrared fiber optical parametric oscillator based on a three-hole suspended-core chalcogenide fiber.

A mid-infrared fiber optical parametric oscillator is proposed and designed based on a three-hole As(2)S(5) suspended-core fiber (SCF). The eigenmodes of the SCF are depicted and the pump condition for single-mode operation is analyzed. The zero-dispersion wavelength is shifted to 2 μm by tuning the core diameter of the SCF. Using the degenerate four-wave mixing coupled-wave equations, a tuning range of the idler wavelength from 2 to 5 μm and a maximum conversion efficiency of 19% are numerically predicted in a 0.1-m-long SCF pumped by a 2.7 W thulium-doped fiber laser.

Mid-infrared fiber optical parametric oscillator using a three- hole suspended-core chalcogenide fiber

A three-hole As2Ss suspended-core fiber with a zero-dispersion wavelength of 2 μm is proposed to construct a mid-infrared (MIR) fiber optical parametric oscillator (FOPO). The numerical model of the MIR FOPO is established and a tuning range from 2 to 5 μm fo r the idler light is predicted.

Side-Opened Suspended Core Fiber-Based Surface Plasmon Resonance Sensor

An integrated surface plasmon resonance (SPR) based on an Au-film-coated, side-opened suspended core fiber is proposed and simulated to develop a highly sensitive, real-time refractive index sensor. The inner surface of the side-opened hole is supposed to be uniformly deposited with a thin Au film for realizing the SPR operation. Such a sensor not only ensures a fast response time, but also brings up a designing flexibility for SPR biosensing applications. Two potential sensing mechanisms, i.e., monitoring the transmission loss spectrum peak shift and measuring the transmission power change at a fixed wavelength are utilized and analyzed to achieve a better sensitivity. Moreover, our calculation results show that this novel sensor could cover a wide index detection range with an optimized resolution of up to 2.3e-5 refractive index unit.