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The present study reports on a detailed investigation on the transition from amorphous to nanocrystalline silicon carbide films grown by means of reactive radiofrequency magnetron sputtering process at low substrate temperatures T s ranging from 200 °C to 500 °C. Fourier transform infrared spectroscopy (FTIR), optical transmission measurements and atomic force microscopy (AFM) images were used to study the structural and the optical properties of the films. The results clearly show that hydrogen atoms play a crucial role in the nanocrystal nucleation mechanism. The grown of the films is governed by the interactions between hydrogen atoms and SiC amorphous matrix. The FTIR analysis showed an abrupt structural transition from amorphous a-SiC:H to nc-SiC:H films occurred with increasing T s from 250 °C to 300 °C. Upon increasing T s , the extent of crystallization is substantial and reaches (70 ± 2) % for films deposited at 500 °C. In parallel, the total bonded hydrogen content decreases from 30 at.% to less than 6 at.%. The AFM observations confirm the structural changes in the films, and the average grain size reaches a value of about 60 nm. [ABSTRACT FROM AUTHOR]

We propose a low-complexity demapping scheme for multidimensional quadrature amplitude modulation (QAM) format using a bitwise log likelihood ratio (LLR). A multidimensional modulation technique such as eight-dimensional (8D) can improve the optical signal-to-noise ratio tolerance by enlarging the minimum Euclidean distance between multidimensional symbols consisting of the plural QAM constellations. However, the optimal soft demapper for these modulation formats increases computational complexity when the formats have higher dimensions and higher order multilevel signals are involved. The rise in computation complexity comes from the fact that these formats have large number of multidimensional symbols. The proposed algorithm reduces the complexity by using the bitwise LLR of original QAM constellation. Furthermore, the proposed soft demapper is suitable for iterative decoding fed back to soft decision forward error correction, such as binary low-density parity check code, since this algorithm uses only the bitwise LLR. We experimentally verify the decoding performance for 120 GBaud 8D-16QAM of the proposed demapper and iterative decoding and demonstrate over 3900 km wavelength division multiplexed transmission. [ABSTRACT FROM AUTHOR]

Oxygen-containing yttrium hydride films (YHx:O) show interesting photochromic properties under ultraviolet irradiation. In this paper, oxygen-containing yttrium hydride films covered with tungsten oxide were prepared by a direct current magnetron sputtering method. This composite material showed reversible photochromic properties. Furthermore, its coloration speed was faster than that of a single layer of yttrium hydride, and its switching modulation was broader. The photochromic mechanism of the YHx:O/WO 3 thin films was investigated by X-ray diffraction, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy analysis. Oxygen and hydrogen played a key role in the photochromic process of the YH x :O/WO 3 composite films. [ABSTRACT FROM AUTHOR]

We investigate the effect of finite size on the chemical diffusion of deuterium in extremely thin V(001) layers. A five fold increase in the diffusion coefficient is observed at concentrations around 0.2 [D/V], when the thickness of the V is decreased from 28 to 14 atomic layers (≈2.1-4.2 nm). The size dependent deuterium.deuterium interaction energy is argued to be the root of the observed changes as the diffusion rates are similar at low concentrations. The results demonstrate the feasibility of using finite-size effects to enhance the chemical diffusion of light interstitials in solids.Wediscuss the general applicability of these effects to other systems. [ABSTRACT FROM AUTHOR]

Transparent thin films of Al-doped ZnO (AZO), Ga-doped ZnO (GZO) and codoped Al + Ga ZnO (AGZO) were deposited on soda-lime glass by RF magnetron sputtering. The influence of aluminum and gallium concentrations in zinc oxide (ZnO) films on structural and optical properties of thin films were studied. XRD results shown that the obtained films were with a hexagonal wurtzite structure and preferentially oriented perpendicular to the substrate surface. Atomic force microscopy (AFM) evidenced that the type of doping modifies the microstructure of thin films. Raman spectroscopy was used to study structural properties of complex oxides at a local level. Optical transmission measurements show a small decrease of transparency films when the dopant content increases. The shift of the optical band gap of AZO films with increasing Al and Ga content suggest the enhancement of carrier concentration. [ABSTRACT FROM AUTHOR]

We report on investigations of the influence of one dimensional confinement on the diffusion of hydrogen, in the low concentration limit ( α - phase). The confinement is obtained by utilising single crystal Fe/V(001) superlattices, in which hydrogen preferably resides in the V layers. The diffusion along the [110] direction in the V(001) layers can thereby be determined. Activation energy and attempt jump rates are extracted from an Arrhenius analysis. No effects are observed from the confinement on the hydrogen diffusion in the thickness range 7–28 monolayers ( ≈ 1.1–4.2 nm) of V(001). [ABSTRACT FROM AUTHOR]

Bi-based chalcogenides, in the form of thin crystalline films, were deposited at different thicknesses onto highly cleaned glass slides with the aid of vacuum thermal evaporation technique. The influence of thermal annealing on the optical properties of Bi 2 Te 3 -Bi 2 Se 3 films at different thicknesses is investigated in this work. Wavelength dependence of the optical transmittance and reflectance was recorded, for the as-prepared and the annealed films, in the wavelength range from 350 to 2700 nm using a double beam spectrophotometer. Fundamental optical properties such as absorption coefficient and energy band gap were derived based on the measured spectra and film's thickness. We demonstrate in the present work that the synergy of annealing and thickness reduction can be exploited for light transmittance enhancements, and consequently for optoelectronic applications including transparent conductive electrodes. [ABSTRACT FROM AUTHOR]

Bourdon tube, an indicating type pressure measuring instrument is used as a local indicator and display unit. Hence a special technique is needed to transmit and to display the reading of a bourdon gauge at remote location. In this paper, a modified bourdon tube has been proposed which is capable to transmit the measured pressure information via optical domain by employing the method of electro-optic effect in Mach–Zehnder interferometers (MZI). Modification in the bourdon tube is done by fabricating an inductor coil to the arm of the bourdon tube. The movement of the bourdon tube is measured in terms of the voltage drop across the inductor. Voltage drop measured by digital voltmeter, across the inductor coil linearly increases (2.29 V–2.38 V) as pressure increases (0 PSI–40 PSI). Amplification of the voltage drop across the inductor coil is done by instrumentation amplifier and the Optical transmission is done by the electro-optic modulation with the help of the MZI. The voltage required for electro-optic modulation is achieved by the signal conditioning circuit which is connected with the instrumentation amplifier. It has been observed that the variation in the pressure is directly proportional to the intensity modulated light signal which has very good linearity and repeatability. The required theoretical equations along with the experimental results are reported and compared in this paper. [ABSTRACT FROM AUTHOR]

We report measurements of the optical transmission, between 240 and 1040 nm, and electrical resistivity of polycrystalline zirconium thin films as they absorb hydrogen. Both are measured as H 2 pressure is increased up to 880 mbar, at room temperature. Films, 20–22 nm thick, are deposited on fused quartz substrates by e-beam evaporation at 5.3 × 10 −7 mbar base pressure and covered with a 8.0 nm Pd over-coat. The morphology of the films is studied by means of AFM images. The complex refractive indices of Zr and Pd are extracted numerically from the transmission spectra by using a spectral projected gradient method for different hydrogen pressures. The corresponding dielectric functions for various Zr hydrogen concentrations are described with the parametric Drude-Lorentz and Brendel-Bormann (DL & BB) models. The Acceptance-Probability-Controlled Simulated Annealing approach is applied to calculate the parameters of the DL & BB model. This allows us to describe the effect of increasing hydrogen absorption on these parameters and in derived quantities, like the relaxation time and the effective mass of conduction electrons, the electrical resistance, the Fermi energy, and the electronic density of states at the Fermi level. [ABSTRACT FROM AUTHOR]

The present work aimed at studying a new organic-inorganic bis (4-amino quinolinium) hexachloro stanate (II) dihydrate compound. It was prepared and characterized by single crystal X-ray diffraction, X-ray powder, Hirshfeld surface, Spectroscopy measurement, thermal study and photoluminescence properties. It was found to crystallize in the monoclinic system ( P 2 1 / c space group) with the following lattice parameters: a = 7.2558(6) Å, b = 13.4876(5) Å, c = 17.2107(13) Å, β = 102.028 (12)°. Its crystal structure was determined and refined down to an R value of 0.06 and a w R value of 0.087. The structure consisted of two different alternating organic-inorganic layers. The crystal packing was stabilized by N H⋯Cl and O H⋯Cl hydrogen bonds and π-π interactions. Hirshfeld surface analysis was used to investigate intermolecular interactions, as well 2D finger plots were conducted to reveal the contribution of these interactions in the crystal structure quantitatively. The X-ray powder is in agreement with the X-ray structure. Scanning electronic microscopy (SEM) was carried out. Furthermore, the room temperature Infra Red (IR) spectrum of the title compound was analyzed on the basis of data found in the literature. Solid state 13 C NMR spectrum shows ten signals, confirming the solid state structure determined by X-ray diffraction. Thermal analysis shows two anomalies at 380 and 610 °C. The optical properties of the crystal were studied using optical absorption UV–visible and photoluminescence (PL) spectroscopy, which were investigated at room temperature. [ABSTRACT FROM AUTHOR]

A method of transmission in a single mode fiber below the cut-off wavelength is proposed. It makes use of the periodic structure of the frequency response of bimodal fiber link and does not require optical filtering. The throughputs of around 1 Gbps were obtained for 5 km SM fiber at 850 nm. [ABSTRACT FROM AUTHOR]

In this paper, an arbitrary distance optical transmission simulation method for free-space optical communication system is presented. Based on this method, direct point-to-point performance tests between two optical terminals can be realized in the laboratory, and the test results are equivalent to those on-orbit. A theoretical analysis of this method is presented in this paper. Verification experiments showed that there is a good linearity between the incoming power density and output photocurrent of the carbon nanotube (CNT); the relative power difference between the CNT and the charge-coupled device (CCD) camera is 4.75%, which can be ignored compared with the link redundancy. [ABSTRACT FROM AUTHOR]

One of the critical issues for broadband accesss is to test the access network infrastructure and quality of optical signal. The installation and powering up of an optical fiber access networks requires measurement techniques for verifying the link has been configured properly and that its constituent components are functioning correctly. Maintenance functions for a broadband optical access network are classified in two main categories: preventive maintenance and post-fault maintenance. The first one consists of: surveillance (to detect degradation in optical fiber components, or any other anomalous condition not preventing the signal transmission,), testing (to measure and locate any detected degradation or anomalous condition) and control (fiber identification and fiber transfer to allow the testing of the link.). In turn second one consisits of: surveillance (to detect alarms or trouble reports and activate a procedure for restoration), testing (to locate the fault and/or verify the carrier performances after the restoration) and remedy (fiber identification, fiber repair or fiber transfer to restore the link). [ABSTRACT FROM AUTHOR]

In the present paper, highly transparent, monolithic and hydrophobic silica aerogel monoliths were prepared by using tetraethoxysilane (TEOS) as precursor and methyltriethoxysilane (MTES) as co-precursor with different MTES/TEOS molar ratios (M) by two-step acid-base catalyzed sol-gel process followed by supercritical alcohol drying. The molar ratio of TEOS, ethanol (EtOH), water (0.001 M oxalic acid catalyst) and ammonium hydroxide (1 M NHOH) was kept constant at 1:5:3.5:3.5 respectively, while the molar ratio of MTES/TEOS (M) was varied from 0 to 0.75. It has been observed that as the M value increases, the gelation time increases. It has been found that lower (0.25) M values resulted in highly transparent (optical transmission >90 % for a 10 mm thick sample at 700 nm wavelength) and negligible volume shrinkage (<10 %) but less hydrophobic aerogels, whereas higher (0.75) M values resulted in semitransparent (<25 % optical transmission at 700 nm for a 10 mm thick sample) aerogels with >10 % volume shrinkage but excellent hydrophobicity. A good compromise of acceptable optical transmittance (~87 % optical transmission at 700 nm wavelength for a 10 mm thick sample) with negligible volume shrinkage (6 %) were obtained at M = 0.50. The hydrophobicity of the aerogels was tested by measuring the contact angle between a water droplet and silica aerogel surface. The hydrophobicity was confirmed by Fourier transform infra-red spectroscopy and contact angle measurements. the aerogels have been characterized by percentage of volume shrinkage, optical transmittance, scanning electron microscopy, thermal conductivity measurements and thermogravimetric analysis and differential thermal analysis. [ABSTRACT FROM AUTHOR]

Filter bank multicarrier (FBMC) is a favourable candidate for next generation optical access networks due to its capability to operate without a cyclic prefix and its high resilience to synchronization errors in the system. In this paper, we analyze the performance of FBMC in upstream passive optical networks (PON), without the employment of inter optical network unit (inter-ONU) frequency guard bands. By using both experimental work and numerical simulations, the impact of relative time offsets on inter-ONU orthogonality is studied. Furthermore, numerical simulations are also used to study the impact of frequency offsets in such systems. Moreover, comparisons are drawn to orthogonal frequency division multiplexing (OFDM)-based upstream PONs. This paper experimentally demonstrates that imperfect time synchronization impacts all subcarriers in an OFDM system, while it affects only the immediately adjacent subcarriers in an FBMC system, which could be corrected for by the restoration of synchronicity between users. A simple feedback mechanism is experimentally demonstrated to automatically restore orthogonality and synchronization between users in order to validate the practical implementation of the scheme. [ABSTRACT FROM PUBLISHER]

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We proposed coded eight-dimensional (8-D) quadrature amplitude modulation (QAM) and experimentally demonstrated in high baud-rate transmission. Both high baud rate and multilevel modulation techniques are necessary for large capacity long haul transmission without increasing the number of transponders. However, optical signal-to-noise ratio (OSNR) tolerance of higher order modulation is low due to the short minimum Euclidean distance. Therefore, to relax OSNR tolerance by enlarging minimum Euclidean distance, we proposed 8-D modulation formats. The spectral efficiency of the proposed coded 8-D-16QAM, 8-D-32QAM, and 8-D-64QAM is equivalent to polarization division multiplexed (PDM)-8QAM, PDM-16QAM, and PDM-32QAM, respectively. To confirm the applicability of the proposed 8-D modulation to high baud rate transmission, we experimentally demonstrated 96-GBaud 8-D-16QAM wavelength division multiplexed transmission over 5,-252 km using iterative soft output decoding. The line data rate is 576-Gbps and a net rate 478-Gbps. At the same spectral efficiency, 8-D-16QAM using iterative soft output decoding can expand the transmission reach by 1212 km compared to conventional PDM-8QAM. [ABSTRACT FROM PUBLISHER]

Polarization-dependent light transmission property is investigated in two-dimensional plasmonic ladder-like structure in the Near-infrared (NIR) regime of 900 to 1600 nm. The plasmonic ladder-like structures are fabricated using cost-effective laser interference lithography. Optical transmission studies reveal that in the stated NIR regime, the structure has nearly 30 % absolute transmission with respect to air when the long axis is aligned parallel to the polarization axis of the incident excitation and has negligible transmission at the crossed polarization state. The findings have potential implications in designing large area flat NIR polarizers. [ABSTRACT FROM AUTHOR]

The bandgaps of 1.187 eV in non-irradiated nanostructured thin films of Cu(In,Ga)Se2 (CIGSe) and of 1.182 eV in those films irradiated with 10 keV hydrogen ions were determined using optical transmission and reflection spectroscopy at 4.2 K. The observed reduction in the bandgap is assigned to the formation of secondary antisite defect complexes inducing band tails of the density of states in the valence band. [ABSTRACT FROM AUTHOR]

Abstract In this work, we investigated the use of 10-layer InAs quantum dot (QD) as active region of an electroabsorption modulator (EAM). The QD-EAM is a p-i-n ridge waveguide structure with intrinsic layer thickness of 0.4 μm, width of 10 μm, and length of 1.0 mm. Photocurrent measurement reveals a Stark shift of ~5 meV (~7 nm) at reverse bias of 3 V (75 kV/cm) and broadening of the resonance peak due to field ionization of electrons and holes was observed for E-field larger than 25 kV/cm. Investigation at wavelength range of 1,300–1320 nm reveals that the largest absorption change occurs at 1317 nm. Optical transmission measurement at this wavelength shows insertion loss of ~8 dB, and extinction ratio of ~5 dB at reverse bias of 5 V. Consequently, methods to improve the performance of the QD-EAM are proposed. We believe that QDs are promising for EAM and the performance of QD-EAM will improve with increasing research efforts.

Flexible Crystalline Silicon Photovoltaic (Fc-SiPV) modules have attracted enormous attention from academics and the industry as a convenient, lightweight alternative energy source for indoor and outdoor applications with limited load-bearing capacity, curved roofs and higher energy demand buildings. This research article focuses on the development of lightweight, high-efficiency, glass-free crystalline silicon flexible photovoltaic modules composed of a composite sandwich structure with a polymer front layer. The optical, mechanical, and thermal properties of different commercially available polymer materials such as Polyethylene Terephthalate (PET), Tedlar Polyethylene Terephthalate (TPT), Ethylene Chloro Tri Fluoro Ethylene (ECTFE), Poly Vinylidene Fluoride (PVDF), Fluorinated Ethylene Propylene (FEP), and Ethylene Tetra Fluoro Ethylene (ETFE) are analyzed for their suitability as front sheet material for flexible crystalline silicon photovoltaic modules manufacturing. The flexible crystalline silicon mini-modules are developed and fabricated utilizing the different materials mentioned above through conventional industrial lamination technology. These flexible polymer modules are analyzed in terms of their optical, spectral response, current-voltage characteristics and impact of thermal cycling for their suitability for photovoltaic applications. The findings of the article may be helpful for module manufacturers in selecting suitable polymer materials for the development of flexible crystalline modules. [Display omitted] • Evaluation of polymer front materials as replacement of glass in flexible crystalline silicon solar modules. • Study of transmittance and suitability of commercially available polymer materials for fabrication of flexible solar modules. • Effect of polymer material on spectral response and current voltage characteristics were reported. • Identification of most suitable polymer material based on thermal stability and module performance. [ABSTRACT FROM AUTHOR]

Three samples of epitaxial delafossite CuFeO 2 and CuFe 1 − x Ga x O 2 films were grown using Pulsed Laser Deposition techniques in high vacuum. The sample thicknesses were estimated to be 21 nm, 75 nm for the CuFeO 2 films and ~ 37 nm for the composite sample containing gallium. The estimated gallium fraction of substituted ferric atoms was x = 0.25 for the composite sample. We present the study of the fundamental band gap(s) for each sample via observation of their respective optical absorption properties in the NIR-VIS region using transmittance and diffuse reflection spectroscopy. Predominant absorption edges measured at 1.1 eV and 2.1 eV from transmittance spectra were observed for the CuFeO 2 samples. The sample of CuFe 1 − x Ga x O 2 showed a measurable shift to 1.5 eV of the lower band-gap and a strong absorption edge located at 2.3 eV attributed to direct band to band transitions. This study also found evidence of changes between apparent absorption edges between transmittance and diffuse reflectance spectroscopies of each sample and it may be resultant from absorption channels via surface states. [ABSTRACT FROM AUTHOR]

This work presents a method that has been recently adopted in our laboratory to determine the temperatures of blackbody sources in the range of 1200-1570 K. The system uses a Double Monochromator System (DMS) based on a grating and a prism as dispersion elements. The detection element was a silicon photodiode (Si-MMA), over which the spectral range from 800nm to 900nm has been used. Between the blackbody source and the DMS was placed an optical system consists of two convergent lenses. The system responsivity "G" was determined by the transmission factor of the optical system and the transmission factor of the DMS and the photodiode responsivity. The obtained results showed that the relative uncertainty of the system responsivity "G" varied from 0.3% to 1.12%. This in turn resulted in a corresponding uncertainty in temperature of about 2.2K and 4.5K (k=1) over the evaluated temperature range. Although this uncertainty level was significantly high compared to those obtained by many other national metrology institutes, it was considered as a step forward in our laboratory to measure high temperatures. [ABSTRACT FROM AUTHOR]

A photovoltaic module is a multi-stack system, compound of a semiconductor generally made of silicon, protected on is upper face a polymer encapsulant and a glass layer. The most usually employed polymer is ethylene-vinyl acetate (EVA) because of its moderate cost and its ease of implementation. However, an extended exposure on UV cause a loss of adhesion and a reduction of the optical transmission (phenomenon of yellowing). Although new formulations of EVA were developed, incorporating antioxidants and UV absorbers, the degradation of the optical properties of a module (via encapsulant and anti-reflective coat of the cell) is nowadays the main cause of the decrease of the performance and the efficiency of the photovoltaic system with time. The goal of this work is to evaluate the behavior of the functional optical properties (transmission, reflection) of a standard formulation of EVA during accelerated ageing under UV. An important temperature of lamination (155 °C) seems to be optimal for the optical properties evolution but not for physico-chemical one. [ABSTRACT FROM AUTHOR]

A process of plasma electrodes and optical transmission “window” formation in electrooptical switch (Pockels cell) of high-power laser radiation pulses is studied experimentally and analyzed numerically. A 2-D computer model of a gas discharge, forming the electrodes and allowing for the charged particles transport and reactions kinetics in self-consistent electric field is developed. A time dependence of the optical transmission in various points of the cross section of the cell operating in the two-pulse mode is computed. In the cell center, the calculated dependence is consistent with the optical transmission oscilloscope trace. [ABSTRACT FROM PUBLISHER]

Transmission demand continues to grow and higher capacity optical communication systems are required to economically meet this ever-increasing need for communication services. This article expands and deepens the study of a novel optical communication system for high-capacity Local Area Networks (LANs), based on twisted optical fibers. The complete statistical behavior of this system is shown, designed for more efficient use of the fiber single-channel capacity by adopting an unconventional multilevel polarization modulation (called "bands of polarization"). Starting from simulative results, a possible reference mathematical model is proposed. Finally, the system performance is analyzed in the presence of shot-noise (coherent detection) or thermal noise (direct detection). [ABSTRACT FROM AUTHOR]

Strontium iodide doped with europium (SrI 2 :Eu 2+ ) is a new scintillator being developed for use in high-energy astrophysical detectors with excellent energy resolution. Nonproportionality is the primary limiting factor to improving its energy resolution, although the physics of nonproportionality is not yet fully understood. In the past few years, co-dopants have been used to alter nonproportionality. By irradiating a SrI 2 :Eu 2+ sample with a 2255 Ci 137 Cs source, we explore both the crystal's potential for space-based applications in a radiation environment and this new method of altering nonproportionality. At ~6200 Gy irradiation, a drop of 7.8% at 700 nm and a drop of 14.1% at 450 nm were seen in the transmission spectrum. Nonproportionality was also reduced after irradiation, shifting from 87% to 101% of the theoretical light yield at 32.1 keV, while the 4.7 keV peak decreased 40% closer to its theoretical value. We propose a novel method of altering the nonproportionality of scintillators, using radiation-induced F-centers in place of co-dopants. [ABSTRACT FROM AUTHOR]

Morphologic and thermo-optical properties of liquid crystalline material exhibiting multiple phase transitions were investigated in this work. Investigations were carried out for both the direct (by heating) and the reverse (by cooling) phase transitions. Thermo-morphologic properties of the heterophase regions of phase transitions were investigated. Temperature dependences of the optical transmission were studied, the mean optical density of crystalline state, smectic C, smectic A and nematic mesophases was estimated, temperature widths of the heterophase regions of crystal ↔ smectic C, smectic C ↔ smectic A, smectic A ↔ nematic and nematic ↔ isotropic liquid phase transitions were determined with high accuracy. [ABSTRACT FROM AUTHOR]

Nanocomposite films containing silver nanowires (Ag NWs) and graphene-oxide nanoplatelets (GONPs) were formed on glass, and the nanocomposite films were then transferred to poly(methylmethacrylate) (PMMA) films. Scanning electron microscopy images showed that Ag NWs with a length of 20 μm and a width of 80 nm, together with GONPs with a size of 15 μm, had been formed on the PMMA film and that the Ag NWs on the PMMA film were partially covered with the GONPs. While the transmittance of the PMMA film with the Ag NWs and the GONPs was almost the same as that of the PMMA film with the Ag NWs alone, the corresponding sheet resistance was decreased due to the generation of quaternary nitrogen in the GONPs, which the results of X-ray photoelectron spectroscopy and Raman spectroscopy confirmed. The transmittance and the sheet resistance of the PMMA film containing Ag NWs and GONPs were approximately 90% at 550 nm and 24 Ohm/sq, respectively. [ABSTRACT FROM AUTHOR]

Ultra-high-speed, ultra-large-capacity and ultra-long-haul (3U) are the forever pursuit of optical communication. As a new mode of optical communication, 3U transmission can greatly promote next generation optical internet and broadband mobile communication network development and technological progress, therefore it has become the focus of international high-tech intellectual property competition ground. This paper introduces the scientific problems, key technologies and important achievements in 3U transmission research. [ABSTRACT FROM AUTHOR]

This paper focuses on upstream signaling in TWDM-PON (one of the two systems specified in the new series of ITU-T G.989.x Recommendations for NG-PON2), for what concerns the discovery phase of a new ONU. The key idea is that a new ONU, that needs to be discovered by the OLT, would send a low bit rate signal that is set to a sufficiently low-power level to not affect significantly the upstream transmission performance of already active ONUs. We properly dimension the key physical layer parameters of this technique and demonstrate it experimentally. We named this proposal as “photon ranging” due to its ultralow-power transmission and we experimentally demonstrate its feasibility. As a “side effect” of this study, we had to deeply revise the power penalty generated by the optical interferometric crosstalk, the main impairment that impacts the proposed setup, obtaining new results that may be of interest also in areas not directly related to the specific framework of TWDM-PON. [ABSTRACT FROM PUBLISHER]

In this Letter, the authors report on the design, optimisation and electrical measurements of a new fully integrated multiplexing selector fabricated in 0.7‐µm indium phosphide (InP) double‐heterojunction bipolar transistor technology. All parts of the circuit were optimised to obtain 200‐Gbit/s class of operation. They present electrical performances at 140 and to a record speed of 212 Gbit/s, highlighting their respective measurement challenges. The power consumption of the circuit is 0.5 and 0.8 W for a differential output amplitude of 240 and 730 mV, respectively. This selector has been successfully used as modulator driver in optical transmission experiments up to 204 Gbit/s. [ABSTRACT FROM AUTHOR]

The principal difference in the origin of high-order optical nonlinearities caused by metallic nanoparticles embedded destructively in oxide- and chalcogenide-type glassy matrices is justified from the viewpoint of a chemical-bond approach. The numerical χ-criterion is introduced to describe this difference in terms of energetic barrier between the mean molar bond energies character for inner chemical interaction of destructed components of a host glassy matrix and guest implanted atoms such as Cu, Ag, and Au. It is confirmed that destructive clustering of metallic nanoparticles is possible in hard dielectric media like oxide glasses possessing a strong negative χ-criterion. [ABSTRACT FROM AUTHOR]

This paper deals with optical bistability and transmission of a nano Fabry-Perot (FP)-resonator which includes two reflectors consisting of one dimensional periodic slabs with negative and positive index materials, and a nanocavity sandwiched between the reflectors. At first, we analyze transmission of the linear FP-resonator with transfer matrix method in optical regime and then, we incorporate gain in nanocavity and investigate the influence of it on transmission. Finally, we study optical bistability in this structure compared to the case with conventional media and the effect of frequency on its hysteresis. According to the results, this structure can be used as an optical switching device and also can be utilize for nanolasers. [ABSTRACT FROM AUTHOR]

It is proposed that using Ethernet in the fronthaul, between base station baseband unit (BBU) pools and remote radio heads (RRHs), can bring a number of advantages, from use of lower-cost equipment, shared use of infrastructure with fixed access networks, to obtaining statistical multiplexing and optimised performance through probe-based monitoring and software-defined networking. However, a number of challenges exist: ultra-high-bit-rate requirements from the transport of increased bandwidth radio streams for multiple antennas in future mobile networks, and low latency and jitter to meet delay requirements and the demands of joint processing. A new fronthaul functional division is proposed which can alleviate the most demanding bit-rate requirements by transport of baseband signals instead of sampled radio waveforms, and enable statistical multiplexing gains. Delay and synchronisation issues remain to be solved. [ABSTRACT FROM AUTHOR]

Sulfide and oxysulfide bulk glasses Ga-La-S-O, Ge-Ga-S and Ge-Ga-As-S doped, or co-doped, with various rare-earth (RE 3+ ) ions are investigated for their room temperature transmission and low-temperature photoluminescence. Photoluminescence spectra are collected by using external excitation into the Urbach tail of the fundamental absorption edge of the host-glass. The low-temperature photoluminescence spectra are dominated by the broad-band luminescence of the host glass, with superimposed relatively sharp emission bands due to radiative transitions within 4f shells of RE 3+ ions. In addition, the dips in the host-glass luminescence due to 4f-4f up-transitions of RE 3+ ions are observed in the Ge-Ga-S and Ge-Ga-As-S systems. These superimposed narrow effects provide a direct experimental evidence of energy transfer between the host glass and respective RE 3+ dopants. [ABSTRACT FROM AUTHOR]

Structural and optical properties of two series of hydrogenated silicon films prepared by reactive radiofrequency magnetron sputtering technique at low substrate temperature, and with applied rf-powers of 150 W (series A) and 300 W (series B) were investigated. The Fourier transform infrared spectroscopic analysis showed changes in the nature of SiH bonding absorption spectra for both wagging and stretching vibration modes between the two series films. By varying the electrode gap spacing, D, (D = 5, 6 and 7 cm) and keeping all the parameters of the plasma constant, a gradual change in the hydrogen-bonding configurations was also observed. The effects of this change, on the structural and the optical properties of the material, were studied by means of Raman spectroscopy and spectroscopic ellipsometry (1.5–5 eV) measurements, complemented with standard optical transmission. The results of this investigation clearly show that the films of the series A present a completely amorphous structure whatever are the D value, with a constant band gap E T of 1.68 eV, typical of hydrogenated amorphous silicon (a-Si:H) films; the decrease in D leads only to an increase in the film compactness. However, the films of the series B are well crystallized, and exhibit a mixture of small and large Si crystallite sizes. Both the volume fractions of these crystallites, F c , increase with decreasing in D. The optical gap shows decreasing trend, with constant hydrogen content, as F c increases. The values of E T lie between those of a-Si:H and c-Si materials, and consequently they have been attributed to the increase in F c values. It is suggested that ion bombardment plays a crucial role in increasing the compactness of the films and one or more specific properties. [ABSTRACT FROM AUTHOR]

The current standard material used for transparent electrodes in displays, touch screens and solar cells is indium tin oxide (ITO) which has low sheet resistance (10 Ω/□), high optical transmission in the visible wavelength (85%) and does not suffer of optical haze. However, ITO is mechanically rigid and incompatible with future demands for flexible applications. Graphene materials share many of the properties desirable for flexible transparent conductors, including high optical transparency, high mechanical flexibility and strength. Whilst pristine graphene is not a good transparent conductor, functionalised graphene is at least 1000 times a better conductor than its pristine counterpart and it outperforms ITO. Here the authors review recent work on a novel graphene‐based conductor with sheet resistance as low as 8.8 Ω/□ and 84% optical transmission. This material is obtained by ferric chloride (FeCl3) intercalation into few‐layer‐graphene (FLG), giving rise to a new system which is the best known flexible and transparent electricity conductor. FeCl3‐FLG shows no significant changes in the electrical and structural properties for a long exposure to air, to high levels of humidity and at temperatures of up to 150°C in atmosphere. These properties position FeCl3‐FLG as a viable and attractive replacement to ITO. [ABSTRACT FROM AUTHOR]

CaF 2 nanoparticles doped with different Er concentrations were synthesized by a co-precipitation method. The phase compositions and morphology of the obtained Er:CaF 2 nanoparticles were characterized by X-ray diffraction and transmission electron microscopy analysis. It was found that the size and shape of obtained CaF 2 nanoparticles were modified through Er 3+ doping. High quality Er:CaF 2 transparent ceramics were fabricated by hot-pressed sintering method in a vacuum environment. The influence of Er 3+ doping concentrations and sintering temperatures on optical transmission and microstructure of Er:CaF 2 transparent ceramics were investigated. When doped with 5 mol% Er 3+ , the CaF 2 ceramic sintered at 800 °C showed the best optical transmission, and for the 2 mm thickness sample, the optical transmission reached about 90% in the near-infrared spectral region. [ABSTRACT FROM AUTHOR]