Optical Fiber Waveguides Research Articles

Optical profile: A key determinant of antibacterial efficacy of photodynamic therapy in dentistry

BackgroundPeriodontal disease effects 20–50% of the population worldwide, posing a global health challenge. It has been reported to be more prevalent among adults. Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) is an important organism associated with localized juvenile periodontitis. Photodynamic therapy (PDT) has been widely utilized for the treatment of periodontal disease; however, the effect of laser (light) profile on the antibacterial efficacy of PDT remains to be established. The quantitative measurement of laser profile is required to confirm the in vitro efficacy of PDT. AimIn the present study, a low cost PDT system comprising of six copper tube waveguides (CTW) was developed to provide more uniform irradiation of the culture plate. MethodsThe antibacterial effect of PDT, in combination with 200 μg/mL methylene blue (MB) as photosensitizer and 60 sec of irradiation, was studied on A. actinomycetemcomitans and Streptococcus mutans (S. mutans). In the present case, 660 nm laser guided with unpolished CTW, polished CTW, and optical fiber waveguide (OFW) provided radiant exposure of 0.86, 1.38, and 1.36 J/cm2, respectively, for a 24‐well culture plate. ResultsThe designed PDT system provided antimicrobial efficacy of 98% and 91% for A. actinomycetemcomitans and S. mutans, respectively, which was significantly higher as compared to OFW guided PDT. ConclusionThe results of the study highlighted the importance of laser profile as a key parameter that determines the survival rate of bacteria at the edge of the culture plate. Thus, the dose of PDT at the margin of optical profile is important for antibacterial activity for in vitro evaluation.

Fiber optic coupled survey meter for NORM and low-level radioactivity monitoring

Currently existing low-level gamma-ray monitoring and measurement devices in the oil and gas and minerals beneficiations industries have several operational limitations, typically including an inability to be operated in an intrinsically safe mode, restrictions in making remote measurements, and an inability to operate in aqueous or high temperature environments. Herein, characterization is made of an optical fiber system based on a LYSO:Ce scintillator, investigated at dose rates and contamination levels comparable to that in dealing with NORM. The measurements were calibrated against a Geiger Muller (GM) pancake counter. The scintillators produce radioluminescence (RL), propagating in the optical fiber waveguide to the photodetection system, providing real-time, remote and intrinsically safe radiation measurements of NORM and other low-level gamma emissions. The response has been found to be dependent on the orientation of the scintillator axis with respect to the source centre. The LYSO:Ce scintillator has been found to be responsive to naturally radioactive sources, tested using monazite and xenotime offering in-contact dose rates down to 20 μSv/h. The measurements were found to be comparable to that of the GM based measurements, further providing intrinsically safe RL remote capabilities, the study pointing to the potential use of scintillation based optical fiber dosimetry systems for NORM and low gamma-ray level measurement in a variety of industrial scenarios.

Mechanically robust amino acid crystals as fiber-optic transducers and wide bandpass filters for optical communication in the near-infrared

Organic crystals are emerging as mechanically compliant, light-weight and chemically versatile alternatives to the commonly used silica and polymer waveguides. However, the previously reported organic crystals were shown to be able to transmit visible light, whereas actual implementation in telecommunication devices requires transparency in the near-infrared spectral range. Here we demonstrate that single crystals of the amino acid L-threonine could be used as optical waveguides and filters with high mechanical and thermal robustness for transduction of signals in the telecommunications range. On their (00bar 1) face, crystals of this material have an extraordinarily high Young’s modulus (40.95 ± 1.03 GPa) and hardness (1.98 ± 0.11 GPa) for an organic crystal. First-principles density functional theory calculations, used in conjunction with analysis of the energy frameworks to correlate the structure with the anisotropy in the Young’s modulus, showed that the high stiffness arises as a consequence of the strong charge-assisted hydrogen bonds between the zwitterions. The crystals have low optical loss in the O, E, S and C bands of the spectrum (1250−1600 nm), while they effectively block infrared light below 1200 nm. This property favors these and possibly other related organic crystals as all-organic fiber-optic waveguides and filters for transduction of information.

Wireless Optogenetic Modulation of Cortical Neurons Enabled by Radioluminescent Nanoparticles.

While offering high-precision control of neural circuits, optogenetics is hampered by the necessity to implant fiber-optic waveguides in order to deliver photons to genetically engineered light-gated neurons in the brain. Unlike laser light, X-rays freely pass biological barriers. Here we show that radioluminescent Gd2(WO4)3:Eu nanoparticles, which absorb external X-rays energy and then downconvert it into optical photons with wavelengths of ∼610 nm, can be used for the transcranial stimulation of cortical neurons expressing red-shifted, ∼590-630 nm, channelrhodopsin ReaChR, thereby promoting optogenetic neural control to the practical implementation of minimally invasive wireless deep brain stimulation.

Robust Mode Matching between Structurally Dissimilar Optical Fiber Waveguides

Robust low-loss optical fiber joints are a prerequisite in all-fiber devices. Joining structurally dissimilar fibers, such as microstructured optical fibers, is a timely challenge, as they are beco...

Multimodal Functional Analysis Platform: 2. Development of Si Opto-Electro Multifunctional Neural Probe with Multiple Optical Waveguides and Embedded Optical Fiber for Optogenetics.

We have developed a Si opt-electro multifunctional neural probe with multiple waveguides and embedded optical fiber for highly accurate optical stimulation. The Si opt-electro multifunctional neural probe had 16 recording sites, three optical waveguides, and metal cover for suppressing light leakage. The other opt-electro multifunctional neural probe had an optical fiber in the trench of the probe shank, which leads to fewer damages to tissues. We evaluated the electrochemical properties of the recording sites and confirmed that the neural probe had suitable characteristics for neural recording. We also demonstrated the optical stimulation to the neurons expressing ChR2 using our probe. As a result, we succeeded in multisite optical stimulation and observed that no light leakage from the optical waveguides because of the metal cover. From in vivo experiments, we successfully recorded optically modulated local field potential using the fabricated Si neural probe with optical waveguides. Moreover, we applied current source density analysis to the recorded LFPs. As a result, we confirmed that the light-induced membrane current sinks in the locally stimulated area. The Si opto-electro multifunctional neural probe is one of the most versatile tools for optogenetics.

Social spider optimization based optimized heat management for wet‐electrospun polymer fiber

AbstractAn electrostatic fiber manufacture method called electrospinning, displayed more attention because of its adaptability and applications in various fields. The polymer fibers named wet‐electrospun (WES) are promising structure for little, adaptable optical fiber devices, for example, lasers, sensors, and waveguides. The shape of WES polymer fibers are represented with aninnate barrel shaped geometry similar to optical fibers that can be created using minimal effort and low‐vitality producing procedures. The loss obtained before the heating process is 17.0 dB cm−1. Here, the loss caused by propagation in WES fibers is reduced using a versatile heat treatment approach (HTA). Also, this HTA significantly reduces the loss in the range of 8.1 dB cm−1 at a wavelength of 533 nm, as the fibers are heated over 49.8°C, which is the glass transition temperature. The propagation loss is also tested for the following 350, 400, 450, 500 nm wavelengths and shown better results. Also, heating conditions are optimized at a wavelength (533 nm) to decrease the propagation loss below 5 dB cm−1. For this calculation social spider optimization (SSO) based optimized temperature rising method is proposed. The proposed method is simulated in the MATLAB platform. Thus, the loss minimization is attributed to excess light scattering (LS) that can be reduced by reducing the propagation loss in WES PDLLA (Poly racemic blend of D, L‐lactic acid units) fibers by effective heat treatment approach.

Polarisation changes in guided infrared thermography using silver halide poly-crystalline mid-infrared fibre bundle

Broadband mid-infrared (B-MIR) thermography using fibre optic waveguides can be critical in real-time imaging in harsh environments such as additive manufacturing, personalised medical diagnosis and therapy. We investigate the polarisation effect on thermal measurements through poly-crystalline fibre bundle employing a simple broadband cross-polarisation configuration experimental set-up. Silver halide poly-crystalline fibres AgCl1−xBrx (0 ≤ x≤1) (AgClBr-PolyC) have very wide transmission bandwidth spanning over the spectral range from 1 µm up to 31 µm FWHM. Moreover, they are non-toxic, non-hygroscopic, with relatively good flexibility, which make them very adequate for spectroscopic and thermal measurements in medical and clinical fields. In this study, we used a fibre bundle composed of seven single AgClBr-PolyC fibres, each with a core diameter of about 300 µm, inserted between two broadband MIR polarisers.A silicon carbide filament source was placed at the entrance of the fibre bundle, while a FLIR thermal camera with a close-up lens was employed to measure the spatial temperature distribution over the fibre-bundle end. Indeed, polarisation dependence of temperature measurements has been clearly observed in which the orientation of temperature extrema (minima and maxima)vary from one fibre to another within the bundle. Moreover, these observations have enabled the classification of AgClBr-PolyC fibres following their polarisation sensitivities by which some fibres are relatively highly sensitive to polarisation with polarisation temperature difference (PTD) that can reach 22.1 ± 2.8 °C, whereas some others show very low PTD values down to 3.1 ± 2.8 °C. Many applications can readily be found based on the advantages of both extreme cases.

Observation of Rapid Adiabatic Passage in Optical Four-Wave Mixing.

We observe clear evidence of adiabatic passage between photon populations via a four-wave mixing process, implemented through a dispersion sweep arranged by a core diameter taper of an optical fiber. Photonic rapid adiabatic passage through the cubic electric susceptibility thus opens precise control of frequency translation between broadband light fields to all common optical media. Areas of potential impact include optical fiber and on-chip waveguide platforms for quantum information, ultrafast spectroscopy and metrology, and extreme light-matter interaction science.

Lossy mode resonance generated by titanium dioxide nanoarray: a comprehensive theoretical research

The lossy mode resonance (LMR)-based optical fiber waveguide based on titanium dioxide nanoarrays was discovered and researched for the first time in this paper. Two kinds of waveguide coating structures, titanium dioxide nanoarrays and nanofilms-nanoarrays systems, were researched using finite element method, where the localized field distribution, the mode transmission characteristics and measurement sensitivities of surrounding refractive index were researched in detail. In the former structure, there exists a localized electromagnetic field that can be generated by both TE and TM polarization modes around nanoarrays. By increasing the diameters of nanoparticles and decreasing the intervals of nanoarrays, the resonance wavelength will redshift and the measurement sensitivity will be enhanced. In the latter structure, the localized electromagnetic field can be obviously enhanced due to the mode coupling between nanofilms and nanoarrays. In addition, the measurement sensitivity of refractive index was 5179 nm/RIU in the range of 1.333–1.343, which is two times higher than that of the structure without TiO2 nanoarrays. This paper opened up a door to study the LMR generated by semiconductor nanoparticles, which is useful in the research of electromagnetic resonance-based sensors in nanoscales.

Thermo-optical properties of binary one dimensional annular photonic crystal including temperature dependent constituents

Abstract In this research article , we present theoretical and numerical investigations concerning the effects of temperature on the transmittance properties of one dimensional annular photonic crystals. The theoretical basis of our study adopts the modified transfer matrix method applied to optical fiber waveguides. The numerical results showed many features that could be of interest. In this regard , we investigate this design to enhance the values of sensitivity based on its geometry. Our design exhibits a remarkable response to temperature changes with a sensitivity of about 0.033 nm/°C which is considered significantly high . Also, it is found that the upper edge of the photonic band gap increases considerably with temperature changes, while the lower edge is almost unchanged . The effects of the core radius and number of periods on the transmittance of our annular photonic crystals design have been also investigated. It is found that an appropriate choice for the core would give flexibility of fabrication and stability of transmission output. In addition, this study reveals that the phase shift of the reflected cylindrical waves within the core is strongly dependent on temperature. We believe our structure is potentially promising in designing and fabrication of novel high-performance temperature sensors and integrated waveguide devices such as optical switches and filters.

Elliptical fibre dielectric waveguides: a transverse transmission line analysis

The authors present a new method for determining the optical properties of arbitrary refractive index elliptical core fibres. The method applies the elliptic cylindrical coordinate system to Maxwell's equations and appropriately, using Fourier Transforms, operated on an elliptical core optical fibre waveguide, derives a flexible algorithm, which can be used to determine the optical properties of elliptical fibre waveguides. By dividing the fibre into a series of uniform consecutive thin dielectric layers transversely across the elliptical cross section with suitable transforming functions representing voltage and current themselves based on the electromagnetic field components, leads to transverse transmission line equations. The resonance frequencies of the cascaded matrices determine the mode propagation constants. The analysis leads to a numerical algorithm for calculating the exact modes of propagation constants. The method is analytically exact and computationally accurate, leading to algorithmic implementation, without making use of Mathieu functions which are solutions for step index waveguide. The advantage of this work is also the fact that it can be applied to arbitrary refractive index profiles. They present results of modal b ¯ − V diagrams for various fibre ellipticities and also apply this method to determine the birefringence of graded index profile fibres and mode cut-off frequencies.

Polymer micro-lenses as an long-coupling-distance interfacing layer in low-cost optical coupling solution between optical fibers and photonic integrated waveguide circuits

We present a low-cost scheme for non-permanent optical signal coupling for prospective application in single use photonic integrated chips. The proposed scheme exploits the use of polymer kinoform microlenses. The feasibility of the proposed solution is demonstrated by the experimental investigation of the optical signal coupling from single mode optical fiber (SMF) to the test structure of SixNy integrated waveguide. Full Text: PDF ReferencesM. Smit et al., "An introduction to InP-based generic integration technology," Semiconductor Science and Technology, 29 (8), 083001, 2014 CrossRef R. Baets et al., "Silicon Photonics: silicon nitride versus silicon-on-insulator," in Optical Fiber Communication Conference, OSA Technical Digest (online) (Optical Society of America, 2016), paper Th3J.1. CrossRef K. Shiraishi et al., "A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers," Appl. Phys. Lett. 91, 141120 (2007) CrossRef Y. Sobu et al., "GaInAsP/InP waveguide dual core spot size converter for optical fiber,"IEEE Photonic Society 24th Annual Meeting, 469-470, (2011). CrossRef F. Van Laere et al., "Compact and Highly Efficient Grating Couplers Between Optical Fiber and Nanophotonic Waveguides," Journal of Lightwave Technology, vol. 25, no. 1, pp. 151-156, Jan. 2007. CrossRef A. Kaźmierczak et al., "Light coupling and distribution or Si3N4/SiO2 integrated multichannel single mode sensing system," Opt. Eng. 48, 2009, pp. 014401 CrossRef M. Rossi et al., "Arrays of anamorphic phase-matched Fresnel elements for diode-to-fiber coupling," Appl. Opt. 34, 2483-2488 (1995) CrossRef M. Prasciolu et al, "Fabrication of Diffractive Optical Elements On-Fiber for Photonic Applications by Nanolitography," Japanese Journal of Applied Physics, Volume 42, (2003) CrossRef F.Schiappelli et al., "Efficient fiber-to-waveguide coupling by a lens on the end of the optical fiber fabricated by focused ion beam milling" Microelectronic Engineering Volumes 73-74, pp.397-404 (2004) CrossRef

Nonreciprocal propagation in optical fibers

Nonreciprocal propagation in the structures compatible with optical fiber waveguides presents practical interest. The present work treats the problem of nonreciprocal propagation in nonabsorbing cylindrically layered structures at axial magnetization characterized by magneto-optic electrical permittivity, , and magnetic permeability, , tensors, using transverse circularly polarized representation. The solutions to the vector Helmholtz Eqs. restricted to the terms linear in the off-diagonal elements of and are expressed analytically. The results are applied to a magneto-optic circular cylindrical waveguide and illustrated on fiber waveguides with an yttrium iron garnet (YIG) core and a cladding formed by gallium substituted yttrium iron garnet (GaYIG) at the optical communication wavelength of 1.55 μm. The propagation distance in the waveguide for a azimuth rotation of a transverse linearly polarized incident wave on the waveguide axis required in isolators is about 100 μm.

Comparison of Self-Injection Locking of DFB-LD by Optical Fiber and Optical Waveguide Ring Resonators

ABSTRACTUtilizing the frequency selection characteristic of ring resonators, self-injection-locking linewidth narrowing and frequency stabilization of distributed feedback laser diodes (DFB-LDs) can be achieved under the aid of ring resonators. In this paper, the self-injection-locking effects of a DFB-LD realized by two fiber ring resonators and an optical waveguide ring resonator are compared. The influences of the resonant peak bandwidth and transmission on linewidth narrowing are demonstrated. It is shown that the mode hopping can be significantly suppressed by employing the optical waveguide ring resonator. This is of great significance for practical applications and integration of the self-injection-locked DFB-LDs.

On-Orbit Self-Focusing Using Conjugated Optical Fiber Waveguides for Space Optical Cameras

High-precision focusing of space optical cameras is the prerequisite for capturing high-quality images in earth observation applications. On-orbit focusing methods are basically based on image-processing algorithms. However, these focusing methods have several limitations, such as calculation complexity, low reliability, and high susceptibility to noises. We propose a real-time self-focusing method using conjugated optical fiber waveguides, which can measure the focal length of on-orbit cameras in real time. We use two conjugated optical fiber waveguides. At one end of each waveguide, there is a light source located external to the camera. The light is guided into the focal plane of the camera and it acts as an infinite point target. Contrary to image processing algorithm, our method is based on the optical components for focusing.

Radiation effects on phosphate glasses: Review

AbstractGlass and its properties are subject to a variety of changes under the influence of high energy radiation. Therefore, radiation‐induced defects in glasses requires high attention due to the wide application of glasses in optics on board space craft, in image guides for reactor inspection, in optical fiber waveguide and in mobilization of high level radioactive waste, for example . In this paper, we present a mini review on radiation effects on phosphate glasses. We review the influence of various irradiation sources on the response of phosphate glasses, focusing on the advances over the past decades.

Study of a silica glass SiO2-Na2O refractive index to fabrication of fiber optic with Brewster method

<p align="justify">One of the critical parameters in the fabrication of fiber optic is refractive index value from the fiber optic material. That is because the main requirement phase of critical angle on the fiber optic waveguide is a core refractive index higher than the cladding. Therefore, refractive index values must be calculated first. The research aim is to study refractive index value of fiber optic material on the fiber optic fabrication. Refractive index value determined by using the brewster method. For this aim, the first step is an establish glass silica to a thin plate. Then thin plate inserts to the sketch of brewster experiment. The brewster method has the aim to determine the reflectance value of the light on transfer magnetic (TM) polarization. The Brewster angle determined by searching the minimum reflectance value of the light on this TM polarization. In this research, the brewster angle obtained by 55.333 degrees. This brewster angle used to calculate the refractive index value from the fiber optic material glass silica. The result of refractive index value at 1.446.</p>

Effects of insertion loss, laser profile and inhomogeneity of dots distribution on properties of all-optical modulator based on GaN/AlN quantum dots

This paper reports the effects of insertion loss, laser profile and inhomogeneity of dots distribution on properties of an all-optical modulator based on spherical quantum dot. The aim of this paper is to give a quantitative description for the variation of main properties of an all-optical quantum dot modulator such as, absorption, transmission and modulation depth regard to insertion loss, laser profile and inhomogeneity of dots. To realize these points, first, we extract the field distribution in optical fiber and channel waveguide (modulator) which are defined by their structure characteristics and boundary conditions. Using the electric field equations, input coupling efficiency and insertion loss and also role of laser profile are observable. Finally we investigate the effect of size distribution and inhomogeneity of quantum dots on the modulator performance. In this structure we used electromagnetically induced transparency (EIT) in GaN/AlN structure, associated with inter-sublevel transitions.

Novel non-fiber optical metamaterial waveguide for monitoring canal and pipeline structures

The electromagnetic metamaterials are the recent entrants, into the classification of smart materials for structural health monitoring (SHM). Their applications in SHM have raised the curiosity due to their rapid executable speeds in wide-frequency domains. The speed of obtaining health output signals for engineering structures is about 1/100th of the time taken by existing smart material-based frequency domain techniques such as piezoelectric material-based techniques. Recently, we developed an ultra-sensitive near-field sensing technique using metamaterial localized surface plasmon (LSP) ‘sensor’ which produced diagnosable ‘confined surface electromagnetic waves’ for SHM. This paper presents the same near-field sensing technique in the frequency domain but using metamaterial ‘waveguides’ based on propagating surface plasmon polaritons (SPPs)/surface waves. For the experiments, a novel robust metamaterial waveguide coupling zone was designed and applied for monitoring longitudinal and lateral displacements in civil engineering prototype structures such as channels and pipelines. In the context of SHM, coupling zone and metamaterial waveguide resemble fiber Bragg grating (FBG) sensor and optical fiber waveguide, respectively. Thus, if properly realized, these metamaterials can co-exist with the existing FBG/optical fiber techniques for applications in civil engineering.