Low-loss Fiber Research Articles

Low-loss single-mode hybrid-lattice hollow-core photonic-crystal fibre

Remarkable recent demonstrations of ultra-low-loss inhibited-coupling (IC) hollow-core photonic-crystal fibres (HCPCFs) established them as serious candidates for next-generation long-haul fibre optics systems. A hindrance to this prospect and also to short-haul applications such as micromachining, where stable and high-quality beam delivery is needed, is the difficulty in designing and fabricating an IC-guiding fibre that combines ultra-low loss, truly robust single-modeness, and polarisation-maintaining operation. The design solutions proposed to date require a trade-off between low loss and truly single-modeness. Here, we propose a novel IC-HCPCF for achieving low-loss and effective single-mode operation. The fibre is endowed with a hybrid cladding composed of a Kagome-tubular lattice (HKT). This new concept of a microstructured cladding allows us to significantly reduce the confinement loss and, at the same time, preserve truly robust single-mode operation. Experimental results show an HKT-IC-HCPCF with a minimum loss of 1.6 dB/km at 1050 nm and a higher-order mode extinction ratio as high as 47.0 dB for a 10 m long fibre. The robustness of the fibre single-modeness is tested by moving the fibre and varying the coupling conditions. The design proposed herein opens a new route for the development of HCPCFs that combine robust ultra-low-loss transmission and single-mode beam delivery and provides new insight into IC guidance.

Towards high-power, high-coherence, integrated photonic mmWave platform with microcavity solitons

Millimetre-wave (mmWave) technology continues to draw great interest due to its broad applications in wireless communications, radar, and spectroscopy. Compared to pure electronic solutions, photonic-based mmWave generation provides wide bandwidth, low power dissipation, and remoting through low-loss fibres. However, at high frequencies, two major challenges exist for the photonic system: the power roll-off of the photodiode, and the large signal linewidth derived directly from the lasers. Here, we demonstrate a new photonic mmWave platform combining integrated microresonator solitons and high-speed photodiodes to address the challenges in both power and coherence. The solitons, being inherently mode-locked, are measured to provide 5.8 dB additional gain through constructive interference among mmWave beatnotes, and the absolute mmWave power approaches the theoretical limit of conventional heterodyne detection at 100 GHz. In our free-running system, the soliton is capable of reducing the mmWave linewidth by two orders of magnitude from that of the pump laser. Our work leverages microresonator solitons and high-speed modified uni-traveling carrier photodiodes to provide a viable path to chip-scale, high-power, low-noise, high-frequency sources for mmWave applications.

Evaluating the cytotoxicity of Ge-Sb-Se chalcogenide glass optical fibres on 3T3 mouse fibroblasts.

In vivo cancer detection based on the mid-infrared molecular fingerprint of tissue is promising for the fast diagnosis and treatment of suspected cancer patients. Few materials are mid-infrared transmissive, even fewer, which can be converted into functional, low-loss optical fibres for in vivo non-invasive testing. Chalcogenide-based glass optical fibres are, however, one of the few. These glasses are transmissive in the mid-infrared and are currently under development for use in molecular sensing devices. The cytotoxicity of these materials is however unknown. The cytotoxicity of Ge–Sb–Se chalcogenide optical glass fibres on 3T3 mouse fibroblast cells is here investigated. Fibres exposed to four different pre-treatment conditions are used: as-drawn (AD), propylamine-etched (PE), oxidised-and-washed (OW) and oxidised (Ox). To achieve the latter two conditions, fibres are treated with H2O2(aqueous (aq.)) and dried to produce a surface oxide layer; this is either washed off (OW) or left on the glass surface (Ox). Cellular response is investigated via 3 day elution and 14 day direct contact trials. The concentration of the metalloids (Ge, Sb and Se) in each leachate was measured via inductively coupled plasma mass spectrometry. Cell viability is assessed using the neutral red assay and scanning electron microscopy. The concentration of Ge, Sb and Se ions after a 3 day dissolution was as follows. In AD leachates, Ge: 0.40 mg L−1, Sb: 0.17 mg L−1, and Se: 0.06 mg L−1. In PE leachates, Ge: 0.22 mg L−1, Sb: 0.15 mg L−1, and Se: 0.02 mg L−1. In Ox leachates, Ge: 823.8 mg L−1, Sb: 2586.6 mg L−1, and Se: 3750 mg L−1. Direct contact trials show confluent cell layers on AD, PE and OW fibres after 14 days, while no cells are observed on the Ox surfaces. A >50% cell viability is observed in AD, PE and OW eluates after 3 days, when compared with Ox eluates (<10% cell viability). Toxicity in Ox is attributed to the notable pH change, from neutral pH 7.49 to acidic pH 2.44, that takes place on dissolution of the surface oxide layer in the growth media. We conclude, as-prepared Ge–Sb–Se glasses are cytocompatible and toxicity arises when an oxide layer is forced to develop on the glass surface.

Arsenic-free low-loss sulfide glass fiber for mid-infrared supercontinuum generation

A low-loss and Arsenic-free sulfur-based chalcogenide fiber(Ge-Sb-S) was fabricated by a novel process of peeled-off extrusion. The fiber has an optical loss of <2 dB/m in a range from 5 to 6 μm with a minimum loss of 0.87 dB/m at 5.1 μm. A mid-infrared (MIR) supercontinuum (SC) spectrum covering 1.56–7.59 μm was generated from a 22-cm long fiber pumped with a femtosecond laser at 4 μm (−150 fs, 1 kHz). Simultaneously, we demonstrated that the optical fiber has a transmission efficiency of 53% at 4 μm, which is the key significance for applications such as IR night vision, bio-photonics, military defense and environmentally friendly industry.

Comparative Analysis of Highly Sensitive PCF for Chemical Sensing in THz Regime

Nowadays photonic crystal fiber (PCF) is used for sensing purposes in different fields. In this work, we have proposed a PCF based chemical (Benzene and Ethanol) sensor. Finite Element Method (FEM) based software COMSOL 5.3a is used to investigate the numerical characteristics for the proposed structure. From the numerical analysis, we obtained high sensitivity with low losses for an optimum core diameter of 210 µm. Our proposed PCF works on a broad range of core diameters and THz frequency spectra. The fabrication of this model is very simple due to its simplistic design structure. Full Text: PDF ReferencesMd.F.H. Arif, Md.J.H. Biddut, "A new structure of photonic crystal fiber with high sensitivity, high nonlinearity, high birefringence and low confinement loss for liquid analyte sensing applications", Sensing Bio-Sensing Res. 12, 8 (2017). CrossRef P. Kumar, Md.H. Bikash, K. Ahmed, S. Sen, "A Novel Hexahedron Photonic Crystal Fiber in Terahertz Propagation: Design and Analysis", Photonics 6(1), 32 (2019). CrossRef S. Asaduzzaman, K. Ahmed, T. Bhuiyan, T. Farah, "Hybrid photonic crystal fiber in chemical sensing", SpringerPlus 5, 748 (2016). CrossRef Md.S. Islam, J. Sultana, J. Atai, D. Abbott, S. Rana, M.R. Islam, "Ultra low-loss hybrid core porous fiber for broadband applications", App. Opt. 56(4), 1232 (2017). CrossRef S. Atakaramians, S. Afshar, H. Ebendorff-Heidepriem, M. Nagel, B.M. Fischer, D. Abbott, T.M. Monro, "THz porous fibers: design, fabrication and experimental characterization", Opt. Expr. 17(16), 14053 (2009). CrossRef

Experimental investigation of the polarization modulation instability and stimulated Raman scattering in a chalcogenide optical fiber

In this work, a low-loss As2S5 optical fiber with 0.1 dB/m at 1545 nm was designed and fabricated, whose residual birefringence provided an opportunity for investigating the polarization modulation instability (PMI). Using a nanosecond laser operated at ∼1545 nm as the pump source, PMI and the stimulated Raman scattering (SRS) were experimentally investigated in a 3 m As2S5 optical fiber. During the SRS process, the amplified CW signal at 1632 nm and 1633 nm induced the PMI. To the best of our knowledge, this is the first report on the PMI effect induced by the amplified signal in the first-order SRS. The PMI gain was measured to be 24.4 dB at the signal of 1551 nm with the pump power of 20 mW, and the Raman gain was measured to be 31.2 dB at the signal of 1632 nm with the pump power of 41 mW. This investigation on the PMI gain and Raman gain in the As2S5 optical fiber may provide a reference for the development of fiber amplifiers, fiber lasers, and optical communication.

Three-dimensional Fabry–Pérot cavities sculpted on fiber tips using a multiphoton polymerization process

This paper presents 3D Fabry–Pérot (FP) cavities fabricated directly onto cleaved ends of low-loss optical fibers by a two-photon polymerization (2PP) process. This fabrication technique is quick, simple, and inexpensive compared to planar microfabrication processes, which enables rapid prototyping and the ability to adapt to new requirements. These devices also utilize true 3D design freedom, facilitating the realization of microscale optical elements with challenging geometries. Three different device types were fabricated and evaluated: an unreleased single-cavity device, a released dual-cavity device, and a released hemispherical mirror dual-cavity device. Each iteration improved the quality of the FP cavity’s reflection spectrum. The unreleased device demonstrated an extinction ratio around 1.90, the released device achieved 61, and the hemispherical device achieved 253, providing a strong signal to observe changes in the free spectral range of the device’s reflection response. The reflectance of the photopolymer was also estimated to be between 0.2 and 0.3 over the spectrum of interest. The dual-cavity devices include both an open cavity, which can interact with an interstitial medium, and a second solid cavity, which provides a static reference reflection. The hemispherical dual-cavity device further improves the quality of the reflection signal with a more consistent resonance, and reduced sensitivity to misalignment. These advanced features, which are very challenging to realize with traditional planar microfabrication techniques, are fabricated in a single patterning step. The usability of these FP cavities as thermal radiation sensors with excellent linear response and sensitivity over a broad range of temperature is reported. The 3D structuring capability the 2PP process has enabled the creation of a suspended FP heat sensor that exhibited linear response over the temperature range of 20 ºC –120 ºC; temperature sensitivity of ∼50 pm ºC−1 at around 1550 nm wavelength; and sensitivity improvement of better than 9x of the solidly-mounted sensors.

How fluorine minimizes density fluctuations of silica glass: Molecular dynamics study with machine-learning assisted force-matching potential

Transparent silica glass is an indispensable material for today's information technology society as an ultra-low loss optical fiber. Recently, further low-loss optical fibers are demanded due to rapidly expanding information. A small amount of fluorine doping is known to reduce the Rayleigh scattering further by reducing the density fluctuations of silica glass, even though the fluorine is an impurity for the pristine silica glass. This study devoted to answer the riddle of F-doping and an accurate force-matching potential optimized by machine-learning enables us to understand how fluorine remedies the disorders in silica glass. It was found that fluorine mainly replaces an oxygen in tetrahedral SiO4 unit, but also forms five-fold Si, such as SiO4F and SiO3F2 units. The former disrupts silica network, while the latter attenuates the network rigidity by loosening the five Si-O(F) bonds. Since the two local effects of fluorine spreads through the glass network, F-doping prompts silica glass to relax further even at temperature lower than the glass transition (fictive) temperature. Consequently, fluorine minimizes the density fluctuation (thus, Rayleigh scattering) of silica glass at around 1 wt%, although fluorine itself is an impurity for silica glass.

Low loss and polarization-insensitive coupling length for a terahertz fiber directional coupler with symmetric dual-suspended core structure

In this work, a terahertz (THz) fiber directional coupler with a symmetric dual-suspended core structure has been proposed for realizing low loss and polarization-insensitive coupling length in the THz frequency region. The fiber core of the directional coupler consists of two round solid dielectric rods supported by two intersecting thin dielectric layers. Numerical simulations performed using the full-vector finite element method show that a short polarization-independent coupling length can be obtained by adjusting the geometric parameters of the fiber. Moreover, a low-loss THz fiber directional coupling performance can also be achieved at a central frequency of 1.00-THz and approximately 0.16 THz of bandwidth. For example, a coupler with a length of 0.421 cm has a transmission loss of 0.30 dB and 0.26 dB for the x- and y-polarization modes, respectively.

Chalcogenide fibers for Kerr squeezing.

We propose and investigate theoretically the Kerr squeezing of light at a wavelength of 2 µm in chalcogenide fibers with large nonlinearity and-this is the advance-with much reduced attenuation. We present suitably realistic but straightforward designs of low-loss step-index single-mode fibers with the nonlinear Kerr coefficient 3 to 4 orders of magnitude higher than for standard telecommunication fibers, and we give estimations of optimal squeezing for continuous wave laser signal in the considered fibers based on As2S3 or As2Se3 glasses.

Recent progress in germanium-core optical fibers for mid-infrared optics

The search for low-loss and robust optical fibers in the infrared spectrum has always been an important research topic for many investigators. Over the years, fibers of various materials groups have been proposed to obtain ‘the ultimate infrared fiber’. Recently, a new competitive alternative has emerged: the semiconductor-core glass-cladded optical fibers. The excellent bulk materials properties and integrated circuit applications reveals the potential of semiconductors as fiber materials. One of the important photonic materials that has been proposed as a fiber-core material is germanium. In this paper, the development of Ge-based fibers and their optical properties in the mid-infrared spectrum are discussed. The performance of Ge-based fibers has been compared with other semiconductor-core fibers. Recent developments in the area of semiconductor fibers and the future prospects of semiconductors as infrared fiber materials are also discussed.

Analysis of achievable distances of BB84 and KMB09 QKD protocols

Quantum key distribution (QKD) is a proven secured way to transmit shared secret keys using quantum particles. Any adversarial attempt to intercept and eavesdrop secret key results in generating errors alerting the legitimate users. Since QKD is constrained by quantum mechanics principles, the practical transmission of the key at a greater distance is an issue. In this paper, we discover and analyze the key factors associated with transmission media, hardware components and protocol implementation of the QKD system that causes hindrance in distance range. Practical implementation of BB84 and KMB09 protocols is discussed to determine the achievable distance given current technology. We find that by using ultra low loss fiber, short-pulse laser and superconducting nanowire single photon detector the maximum achievable distance for both of the quantum protocols is 250[Formula: see text]km.

Rayleigh scattering characterization of a low-loss MgO-based nanoparticle-doped optical fiber for distributed sensing

We present the fabrication and characterization of a low-loss enhanced backscattering fiber, having the core doped with MgO-based nanoparticles (MgO-NP), for distributed sensing application. The fiber has a scattering increment of 48.9 dB and two-way attenuation of 14.3 dB/m; these are the largest Rayleigh scattering increment paired with the lowest losses for this type of fiber. In this work, we provide a thorough characterization of the fiber performances, and their impact on distributed sensing networks, using scattering-level multiplexing where a 2.4 – 4.0 times extension of sensing length can be achieved.

Weaving light - [Past Forward

Textile artist Suzanne Tick is known for incorporating unusual materials into her weaving: recycled dry cleaner hangers, Mylar balloons washed up on the beach, documents from her divorce. For this work, called Crossform Pendant Lamp, she used industrial fiber-optic yarn, a technology that was more than 150 years in the making. Back in 1841, the Swiss physicist Jean-Daniel Colladon first demonstrated that light could travel along a curved path defined by a stream of water; in 1960, Narinder Singh Kapany coined the term "fiber optics"; and 50 years ago this month, engineers at Corning demonstrated low-loss optical fiber. Tick combines in her sculpture 21st-century side-emitting optical fibers with the millennia-old practice of weaving to allow her lamp to glow from within.

Development of flexible mid-infrared light delivery system with bioprobe for beam control

The objective of this paper is to fabricate a flexible mid-infrared (IR) light delivery system with bioprobesince remarkable biological effect of mid-IR light and lack of corresponding technical devices. Hollow optical fiber with sealing window of different materials and shapes was fabricated and packaged within a metal tube for delivering mid-IR light and electrical signal. The thickness of the sealing window was optimized consideringmechanical strength, loss, and power density threshold. A bioprobe with a SMA connector was manufactured. A patch cord loaded with low-loss mid-IR hollow optical fiber was prepared and can be connected to the bioprobeby a standard SMA jointer. The loss of the bioprobe was 1.38 dB and 1.07 dB at the wavelength of 5.1 μm and 10.6 μm, respectively. The output beam of the bioprobe can be controlled by sealing windows of different shapes, which had a far-field half divergence angle of 0.03–0.44 rad. The system had a power density threshold of 382 mW/mm2 and a loss of 3.44 dB at 10.6 μm. A light delivery system with bioprobe was manufactured, which provided a photoelectric device for the application of mid-IR light in the field of neuroscience. The presented system is of high efficiency electro-optic transmission and of high power density threshold, and the applicable wavelength can be extended to far-IR and terahertz by changing the fabrication process of hollow optical fiber.

Low-Loss Chalcogenide Fiber Prepared by Double Peeled-Off Extrusion

We have developed an innovative extrusion with double peeling-off process to fabricate chalcogenide (GhG) preform, with an aim to remove the defects, such as bubbles, oxidation, and particles that always induce large optical losses in ChG glass fibers. As a result, none of the defects is found in the core-cladding interface of the fiber. The loss in a wavelength range of 5.5–8.2 μm is generally lower than 1 dB/m, with a minimum value of 0.2 dB/m at 6.3 μm. Moreover, a flat mid-infrared (MIR) supercontinuum (SC) spectrum spanning from 1.4 μm to 13.7 μm is generated in an 18 cm-long Ge-As-Se ChG fiber, accompanied with a highest spectrum flatten ratio of 72.4%.

Quantum Walks in Periodic and Quasiperiodic Fibonacci Fibers

Quantum walk is a key operation in quantum computing, simulation, communication and information. Here, we report for the first time the demonstration of quantum walks and localized quantum walks in a new type of optical fibers having a ring of cores constructed with both periodic and quasiperiodic Fibonacci sequences, respectively. Good agreement between theoretical and experimental results has been achieved. The new multicore ring fibers provide a new platform for experiments of quantum effects in low-loss optical fibers which is critical for scalability of real applications with large-size problems. Furthermore, our new quasiperiodic Fibonacci multicore ring fibers provide a new class of quasiperiodic photonics lattices possessing both on- and off-diagonal deterministic disorders for realizing localized quantum walks deterministically. The proposed Fibonacci fibers are simple and straightforward to fabricate and have a rich set of properties that are of potential use for quantum applications. Our simulation and experimental results show that, in contrast with randomly disordered structures, localized quantum walks in new proposed quasiperiodic photonics lattices are highly controllable due to the deterministic disordered nature of quasiperiodic systems.

A silicon‐organic hybrid platform for quantum microwave-to-optical transduction

Low-loss fiber optic links have the potential to connect superconducting quantum processors together over long distances to form large scale quantum networks. A key component of these future networks is a quantum transducer that coherently and bidirectionally converts photons from microwave frequencies to optical frequencies. We present a platform for electro-optic photon conversion based on silicon‐organic hybrid photonics. Our device combines high quality factor microwave and optical resonators with an electro-optic polymer cladding to perform microwave-to-optical photon conversion from 6.7 GHz to 193 THz (1558 nm). The device achieves an electro-optic coupling rate of 590 Hz in a millikelvin dilution refrigerator environment. We use an optical heterodyne measurement technique to demonstrate the single-sideband nature of the conversion with a selectivity of approximately 10 dB. We analyze the effects of stray light in our device and suggest ways in which this can be mitigated. Finally, we present initial results on high-impedance spiral resonators designed to increase the electro-optic coupling.

Si3N4 photonic integration platform at 1 µm for optical interconnects.

Vertical-cavity surface-emitting lasers (VCSELs) are the predominant technology for high-speed short-range interconnects in data centers. Most short-range interconnects rely on GaAs-based multi-mode VCSELs and multi-mode fiber links operating at 850 nm. Recently, GaAs-based high-speed single-mode VCSELs at wavelengths > 1 µm have been demonstrated, which increases the interconnect reach using a single-mode fiber while maintaining low energy dissipation. If a suitable platform for passive wavelength- and space-multiplexing were developed in this wavelength range, this single-mode technology could deliver the multi-Tb/s interconnect capacity that will be required in future data centers. In this work, we show the first passive Si3N4 platform in the 1-µm band (1030-1075 nm) with an equivalent loss < 0.3 dB/cm, which is compatible with the system requirements of high-capacity interconnects. The waveguide structure is optimized to achieve simultaneously single-mode operation and low bending radius, and we demonstrate a wide range of high-performance building blocks, including arrayed waveguide gratings, Mach-Zehnder interferometers, splitters and low-loss fiber interfaces. This technology could be instrumental in scaling up the capacity and reducing the footprint of VCSEL-based optical interconnects and, thanks to the broad transparency in the near-infrared and compatibility with the Yb fiber amplifier window, enabling new applications in other domains as optical microscopy and nonlinear optics.

Polarization filter realization using low-loss hollow-core anti-resonant fiber in THz regime

A Zeonex based loss hollow-core anti-resonant fiber (HC-ARF) for polarization filter (PF) application in the terahertz (THz) spectral range is presented here. The finite element method, a practical and precise computational technique, is used to compute the modal properties of the designed fiber. Simulation results indicate minimum loss of 0.34 dB/m at 1.1 THz, a loss less than 2 dB/m for a large bandwidth of 460 GHz in the horizontal polarization mode (HPM) due to the inclusion of nested tubes in that direction. In addition, a 520 GHz filtering bandwidth with crosstalk higher than 20 dB can be obtained within 1 m of the proposed fiber.