Effects of Triangular Core Rotation of a Hybrid Porous Core Terahertz Waveguide

In this paper, we investigate the effects for rotating the triangular core air hole arrangements of a hybrid design porous core fiber. The triangular core has been rotated in anti-clockwise direction to evaluate the impact on different waveguide properties. Effective Material Loss (EML), confinement loss, bending loss, dispersion characteristics and fraction of power flow are calculated to determine the impacts for rotating the triangular core. The porous fiber represented here has a hybrid design in the core area which includes circular rings with central triangular air hole arrangement. The cladding of the investigated fiber has a hexagonal array of air hole distribution. For optimum parameters the reported hybrid porous core fiber shows a flat EML of ±0.000416 cm-1 from 1.5 to 5 terahertz (THz) range and a near zero dispersion of 0.4±0.042 ps/THz/cm from 1.25 to 5.0 THz. Negligible confinement and bending losses are reported for this new type of hybrid porous core design. With improved concept of air hole distribution and exceptional waveguide properties, the reported porous core fiber can be considered as a vital forwarding step in this field of research

3D printed hollow-core terahertz fibers

CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESPA - FUNDAÇÃO AMAZÔNIA DE AMPARO A ESTUDOS E PESQUISASCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORThis paper reviews the subject of 3D printed hollow-core fibers for the propagation of terahertz (THz) waves. Several hollow and microstructured core fibers have been proposed in the literature as candidates for low-loss terahertz guidance. In this review, we focus on 3D printed hollow-core fibers with designs that cannot be easily created by conventional fiber fabrication techniques. We first review the fibers according to their guiding mechanism: photonic bandgap, antiresonant effect, and Bragg effect. We then present the modeling, fabrication, and characterization of a 3D printed Bragg and two antiresonant fibers, highlighting the advantages of using 3D printers as a path to make the fabrication of complex 3D fiber structures fast and cost-effective.63111CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESPA - FUNDAÇÃO AMAZÔNIA DE AMPARO A ESTUDOS E PESQUISASCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESPA - FUNDAÇÃO AMAZÔNIA DE AMPARO A ESTUDOS E PESQUISASCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORSem informaçãoSem informaçãoSem informaçã

Terahertz optical fibers [Invited]

Abstract not available.Md. Saiful Islam, Cristiano M.B. Cordeiro, Marcos A.R. Franco, Jakeya Sultana, Alice L.S. Cruz, and Derek Abbot

Terahertz Hollow Core Antiresonant Fibre

Research on fibres operating in the terahertz frequency range is rapidly growing with numerous potential applications such as in spectroscopy, imaging, security, and transmission. However, designing a terahertz fibre with controllable and desirable transmission characteristics is challenging due to the complex cladding structure. In this thesis, we study hollow core antiresonant photonic crystal fibre (HC-ARPCF) for electromagnetic transmission and refractometric sensing in the terahertz regime. The HC-ARPCF consists of an air-core surrounded by a structured polymer cladding, which confines most of the power within the air-core region. The idea behind hollow-core antiresonant fibres is that light is guided in the hollow air core, thus drastically reducing the transmission loss. Guidance of light is achieved via reflection provided by thin membranes of the antiresonant tubes that surround the core, behaving effectively as a Fabry-P´erot cavity. At antiresonant frequencies, the thin membranes reflect the light towards the core because of the higher refractive index of the membranes. The guidance mechanism of the HC-ARPCF can also be explained due to the inhibited coupling mechanism (coupling between core and cladding mode is forbidden in guidance), where the cladding mode maintains a lower density of states (ηeff) than the fundamental core mode. Inhibited coupling guidance in HC-ARPCF offers broad bandwidth. At resonance frequencies, the light couples to the thin membranes and the core mode becomes more lossy, which can assist in gas sensing. The idea for the terahertz HC-ARPCF is inspired by those in the well-developed infrared and mid-infrared range. The effect of cladding pattern, cladding material, and cladding sector angle are analysed to investigate and tune the transmission loss, bending loss, and modal properties. The detailed simulations of several designs give a new understanding of the effect of the cladding elements on the leakage loss. The HCARPCFs are considered as a suitable candidate for low loss and broadband terahertz transmission. In addition, we model and simulate a simple hollow-core antiresonant terahertz waveguide, show the linear properties and explore the mechanism of achieving nonlinearity. First, the linear properties of HC-ARPCF are discussed, and then the nonlinear properties of the same structure are demonstrated, considering a gas-filled core in the terahertz regime. Furthermore, this thesis describes two different fabrication techniques for terahertz HC-ARPCF, using Zeonex and UV-resin as the bulk materials via a 3D printing process. The Zeonex filaments are made by using a Filabot EX2 Filament Extruder designed for filament production. To measure the effective material loss of the Zeonex, a circular disc with an uneven thickness of 0.65±0.05mmand a diameter of 24mmis printed.We demonstrate the first successful fabrication of Zeonex and UV resin fibre using Fused Decomposition modelling (FDM) and Steriolithography Apparatus (SLA) methods, respectively, to investigate the surface quality and thickness variations of the printed structure. These printing approaches have potential to replace conventional costly terahertz fibre drawing process. The fabricated fibres are then experimentally investigated for terahertz transmission. Fibres fabricated using the FDM and SLA methods are also investigated numerically and the results are compared against the experimental results. The detailed simulations suggest their attenuation can be improved by orders of magnitude with improvements in the quality of the fabrication process. We also discuss the possible post-processing techniques that can be useful for improving fibre quality and consistency in future work.Thesis (Ph.D.) -- University of Adelaide, School of Electrical & Electronic Engineering, 202

Specialty Fibers for Terahertz Generation and Transmission: A Review

Terahertz (THz) frequency range, lying between the optical and microwave frequency ranges covers a significant portion of the electro-magnetic spectrum. Though its initial usage started in the 1960s, active research in the THz field started only in the 1990s by researchers from both optics and microwaves disciplines. The use of optical fibers for THz application has attracted considerable attention in recent years. In this paper, we review the progress and current status of optical fiber-based techniques for THz generation and transmission. The first part of this review focuses on THz sources. After a review on various types of THz sources, we discuss how specialty optical fibers can be used for THz generation. The second part of this review focuses on the guided wave propagation of THz waves for their transmission. After discussing various wave guiding schemes, we consider new fiber designs for THz transmission

Practical Microstructured and Plasmonic Terahertz Waveguides

La bande térahertz, comprenant les fréquences entre 100 GHz et 10 THz, présente un fort potentiel pour diverses applications technologiques et scientifiques, telles que la détection, l’imagerie, le secteur des communications ainsi que la spectroscopie. La plupart des sources térahertz (THz) sont immobiles et, dans les systèmes THz existants, la propagation de l’onde se fait dans l’air libre, afin de minimiser les pertes de transmission. Le design efficace de guides d’onde THz est important pour des applications pratiques des techniques THz. Ces guides d’onde permettraient une meilleure intégration de plusieurs composants en un système THz unique: les sources, les détecteurs, les filtres etc. L'application la plus évidente des guides d'onde THz est la livraison de l'onde de la source au détecteur. Les composants optiques encombrants pourraient être remplacés et le tout pourrait être incorporé dans un système compact de spectroscopie THz dans le domaine temporel. L'imagerie et la détection sont d'autres avenues prometteuses pour les guides d'onde THz. Il a déjà été démontré que les guides d'ondes THz peuvent opérer en régime sub-longueur d'onde, offrant ainsi un confinement du mode guidé plus petit que la limite de diffraction. Ainsi, la résolution spatiale de ces guides d'onde surpassent celle des systèmes THz conventionnels. Pour un design efficace des guides d'onde THz, il est important de minimiser les pertes et la dispersion. Une solution potentielle serait d'augmenter la fraction de la puissance modale qui se propage dans l'air. Dans cette thèse, nous abordons l'utilisation de guides d'onde air/diélectrique, planaires et poreux, ainsi que de guides d'onde hybrides fils métalliques/diélectriques. D'abord, nous présentons un nouveau design de guide d'onde planaire et poreux. Nous décrivons sa fabrication et nous le caractérisons pour une potentielle application comme guide d'onde et comme senseur dans le spectre THz. Le guide d'onde est formé de plusieurs minces films de polyéthylène (25 - 50 μm) séparés par des couches d'air d'épaisseurs comparables. Une grande portion du champ électrique est guidé dans l'air, permettant ainsi de réduire significativement les pertes par transmission. Également, nous constatons qu'un tel guide d'onde peut s'avérer utile pour des applications de détection biologique et chimique, en plaçant directement les échantillons dans la microstructure. Le guide d'onde planaire proposé possède l'avantage principal de permettre l'accès aisé au mode optique, puisque la majorité de la puissance THz introduite est confiné dans les couches d'air.----------Abstract The terahertz frequency range, with frequencies lying between 100 GHz and 10 THz, has strong potential for various technological and scientific applications such as sensing, imaging, communications, and spectroscopy. Most terahertz (THz) sources are immobile and THz systems use free-space propagation in dry air where losses are minimal. Designing efficient THz waveguides for flexible delivery of broadband THz radiation is an important step towards practical applications of terahertz techniques. THz waveguides can be very useful on the system integration level when used for connection of the diverse THz point devices, such as sources, filters, sensor cells, detectors, etc. The most straightforward application of waveguides is to deliver electromagnetic waves from the source to the point of detection. Cumbersome free-space optics can be replaced by waveguides operating in the THz range, which could lead to the development of compact THz time domain spectroscopy systems. Other promising applications of THz waveguides are in sensing and imaging. THz waveguides have also been shown to operate in subwavelength regimes, offering mode confinement in waveguide structures with a size smaller than the diffraction limit, and thus, surpassing the resolution of free-space THz imaging systems. In order to design efficient terahertz waveguides, the frequency dependent loss and dispersion of the waveguide must be minimized. A possible solution would be to increase the fraction of mode power propagating through air. In this thesis, the usage of planar porous air/dielectric waveguides and metal wire/dielectric hybrid terahertz fibers will be discussed. First, we present a novel design of a planar porous low-loss waveguide, describe its fabrication, and characterize it in view of its potential applications as a low-loss waveguide and sensor in the THz spectral range. The waveguide structure features a periodic sequence of layers of thin (25-50 μm) polyethylene film that are separated by low-loss air layers of comparable thickness. A large fraction of the modal fields in these waveguides is guided in the low-loss air region, thus effectively reducing the waveguide transmission losses. We consider that such waveguides can be useful not only for low-loss THz wave delivery, but also for sensing of biological and chemical specimens in the terahertz region, by placing the recognition elements directly into the waveguide microstructure

Plasmonic and nanophotonics sensors from visible to terahertz

Theory of surface plasmon sensors -- Electromagnetic theory of surface plasmons -- Excitation of surface plasmons -- Methodology -- Design criteria for microstructured-optical-fiber-based surface-plasmon-resonance sensors -- Geometry of a MOF-based SPR sensor -- Excitation of plasmonic waves by the core guided mode of a MOF -- Tuning of plasmonic excitations -- Sensitivities of the MOF-based SPR sensors -- Photonic crystal fiber and waveguide-based surface plasmon resonance sensors for application in the visible and NEAR-IR -- SPR sensors using planar photonic crystal waveguides -- SPR sensors using photonic crystal Bragg fibers -- SPR sensors using microstructured photonic crystal fibers -- Porous polymer fibers for low-loss terahertz guiding -- Porous fibers with multiple sub-wavelength holes -- Porous photonic bandgap Bragg fibers with a network of bridges -- Surface-plasmon-resonance-like fiber-based sensor at terahertz frequencies -- THz plasmon-like excitations -- Sensitivity of a THz SPR-like sensor -- Surface plasmon resonance-like integrated sensor at terahertz frequencies for gaseous analytes -- TH plasmon-like excitation at the PVDF/air interface -- Sensitivity of an SPR-like THz sensor -- Overall discussion and conclusion

Design and Analysis of Advanced Photonic Devices for Electromagnetic Transmission and Sensing

In this thesis, we report the investigation of advanced photonic devices for electromagnetic transmission and biochemical sensing in the terahertz and optical regimes. The choice of material for designing a terahertz device is deemed to be one of the most crucial factors. First, we consider materials that are frequently used in making terahertz devices. We experimentally demonstrate the optical, thermal, and chemical properties of various chosen glasses, polymers, and resin to select the optimal material for terahertz. Second, we perform a broad review on terahertz optical fibres—this includes various fibre categories, their guiding mechanisms, fabrication methodologies, possible experimental methodologies, and applications. Third, we analyse and demonstrate the design of various fibre structures for terahertz transmission and sensing, and then perform experiments on a hollow core antiresonant fibre. We demonstrate successful fabrication of an asymmetrical Zeonex fibre using a novel fabrication method. This is carried out by using a tabletop horizontal extruder designed for producing polymer filaments. The fabricated fibre is then experimentally investigated for terahertz transmission and gas sensing. Fourth, we study optical fibre based surface plasmon resonance biosensors for operation in the optical regime. Theoretical studies are undertaken to obtain the best possible sensor in consideration of performance, experimental feasibility, and fabrication. One of the optimized sensors is then fabricated as a possible candidate for possible realworld sensing applications. Finally, we study metasurface planar devices for achieving high sensitivity and quality factor in the terahertz regime. We first demonstrate a tunable graphene metasurface that can achieve multi-band absorption and high refractometric sensing. Later, we demonstrate on an all-dielectric metasurface that reports highest Q-factor in the terahertz regime. We fabricate and experiment on the dielectric metasurface and find good agreement with the simulation.Thesis (Ph.D.) -- University of Adelaide, School of Electrical & Electronic Engineering, 202