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Expanding gain bandwidth into the L-band for erbium-doped fiber amplifiers (EDFAs) is a crucial strategy to overcome limitations in prevalent C-band focused commercial silica-based EDFAs, significantly boosting optical network transmission capacity. Herein, we synthesized Er3+-doped broadband near-infrared emission tellurite glasses utilizing the melt quenching process, systematically exploring the impact of ZnCl 2 on the glass structure and optical properties. The 82TeO 2 –3Nb 2 O 5 –15ZnCl 2 –3Er 2 O 3 (TNZ15) glass emerged as a standout candidate for broadband amplifiers around wavelength at 1.55 μm. With escalating ZnCl 2 concentration, a discernible red shift in the emission peak wave lines was observed, accompanied by an expansion of the full width at half maximum (FWHM) from 98 nm to 106 nm. Noteworthy characteristics of all samples included exceptional thermal stability and elevated near-infrared (NIR) transmittance. Application of the Judd-Ofelt (J-O) theory facilitated the calculation of J-O parameter intensity, providing deeper insights into the optical behavior of the materials. Finally, the evaluation of TNZ15 planar optical waveguides, employing the vertical top pumping mode of two 980 nm LEDs, encompassed both the C-band (1530–1565 nm) and the L-band (1565–1625 nm). The results underscore the potential of TNZ15 glass as a promising gain material for broadband optical amplifiers and lasers, offering valuable insights into the development of next-generation optical amplification technologies. [ABSTRACT FROM AUTHOR]

This paper reports a broadband near-infrared emission ranging from 1400 to 1660 nm in Er3+-doped nanocrystal-modified PbO-PbF 2 -Bi 2 O 3 -Ga 2 O 3 glasses. After heat treatment, X-ray diffraction measurements were performed and confirmed that PbBiO 2 F nanocrystals were precipitated in the precursor glasses. As nanocrystals alter the local environment around Er3+ ions, the emission spectrum of the transition 4I 13/2 →4I 15/2 is broadened and enhanced, resulting in a broadband emission and an FWHM wavelength range of 143.4 nm from 1470.1 to 1613.5 nm, which overlaps the S+C+L optical communications windows. In addition, the emission intensity of the 4I 11/2 →4I 13/2 transition is also found to be increased after heat treatment, thus enhancing the λ∼2750 nm emission intensity. Our results indicate that an Er3+-doped nanocrystal-modified PbO-PbF 2 -Bi 2 O 3 -Ga 2 O 3 glass could be a competitive candidate material that can offer improved bandwidths for S+C+L broadband amplifiers used in very high-capacity optical communications systems. [ABSTRACT FROM AUTHOR]

In this work, Tm3+ doped and Tm3+/Ho3+ co-doped germanate glasses with various TiO 2 concentrations have been examined using optical spectroscopy. The broad emission bands corresponding to 3F 4 →3H 6 (1.8 μm) and 5I 7 →5I 8 (2 μm) transitions of thulium and holmium ions were registered, respectively. It was observed that the intensity of near-infrared emission bands significantly changes with increasing titanium oxide content in the glass composition. Furthermore, the energy transfer process from Tm3+ to Ho3+ ions in studied glass systems was confirmed and discussed. The dependence of spectroscopic parameters like full width at half maximum (FWHM) and energy transfer efficiency (η ET) on increased TiO 2 concentration in glass host was established. [ABSTRACT FROM AUTHOR]

Dense wavelength division multiplexing (DWDM) is recognized as one of the leading technologies for resolving the internet data traffic capacity issue. Although the successful development of rare-earth doped fiber amplifiers enables to achieve optical signal amplification in various telecommunication wavebands, their bandwidth is limited by the inherent sharp 4f electronic transition. Here, we propose the clustering engineering strategy in tellurium (Te)-doped glass fiber for broadband optical amplification. The correlation among the glass system, chemical state of Te and the optical response are systematically studied. The active Te-doped phosphate glass with intense and broadband luminescence is successfully achieved by control of the cluster state of the Te atoms. Subsequently, Te-activated phosphate fiber is successfully drawn and the optical response is transferred smoothly. Importantly, the amplified spontaneous emission and broadband optical amplification are achieved for the first time in Te-doped glass fiber. A small signal on-off gain covering an ultra-wide range of O + E + S + C + L bands is observed under excitation at 808 nm. Our results establish a critical step toward advancing Te-based photonic materials for novel broadband fiber amplifiers serviced in telecommunication system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tellurite glass with Tm3+/Ho3+/Er3+ combination was developed by melt-quenching method. • A broad luminescence from 1570 to 2200 nm with 379 nm FWHM was obtained under 808 nm pump. • Energy transfer from Er3+ to Tm3+/Ho3+ enhances broadband luminescence intensity by about 116 %. • There are potential applications in ultrashort pulse lasers and broadband amplifiers. Improving the broadband luminescent properties in ∼2 μm band has always been a serious challenge. This paper proposed a Tm3+, Ho3+ and Er3+ doped combination in tellurite glass, which was synthesized through melt-quenching and characterized by a series of physical and spectral tests. Firstly, tellurite glass of Tm3+–Ho3+ co-doping produced a ∼2 μm broadband luminescence ranging from 1570 to 2200 nm with FWHM (full width at half maximum) of 379 nm under 808 nm pumping. This broadband luminescence originated from 3F 4 to 3H 6 level transition of Tm3+ and 5I 7 to 5I 8 level transition of Ho3+. Furthermore, after adding an appropriate amount of Er3+, the luminescent intensity was improved by 116 %, mainly attributed to the direct or indirect energy transfers from Er3+ to Tm3+ and Ho3+ ions. Calculations of Judd-Ofelt spectroscopic parameters and gain cross-sections supported the results obtained from Tm3+/Ho3+/Er3+ doped tellurite glass in ∼2 μm band. In addition, DSC (differential scanning calorimetry) curves exhibited excellent thermal stability, XRD (X-ray diffraction) patterns and Raman spectra disclosed the non-crystalline and network structural units of the synthesized tellurite glasses. The findings in this work demonstrate that tellurite glass with Tm3+, Ho3+ and Er3+ combination is an efficient strategy which can be applied in ∼2 μm band ultra-short pulse lasers and broadband amplifiers. [ABSTRACT FROM AUTHOR]

This paper proposes a generalized design methodology for extending the bandwidth and output back-off range of an equal-cell Doherty power amplifier (EC-DPA). The parameters of the EC-DPA combiner are derived based on pre-defined asymmetrical voltage and nonlinear current profiles. It is illustrated that the design parameters of the EC-DPA can be expressed as a function of the combining load. Then, the combining load can be optimized to extend the bandwidth of the proposed EC-DPA. As a validation, an 1.4–2.1 GHz EC-DPA with extended output back-off range is implemented in this paper. Under a continuous-wave (CW) signal excitation, the fabricated EC-DPA achieves a maximum output power of 42.6–43.8 dBm, a saturation drain efficiency (DE) of 50.2%–70.2% and a 10 dB back-off DE of 45.2%–53.7% over 1.4–2.1 GHz. Moreover, under the excitation of a 20 MHz modulated signal with a peak-to-average power ratio (PAPR) of 8.0 dB, the measured adjacent channel leakage ratios (ACLRs) of the fabricated EC-DPA changes from −36.2 dBc to −25.5 dBc at the lower band and from −34.6 to −23.8 dBc at the upper band over 1.4–2.1 GHz when the average output power is 35.0 dBm. [ABSTRACT FROM AUTHOR]

This paper presents a broadband power amplifier (PA) implemented in 40-nm CMOS process for low power application. The PA cascades two stages of common-source differential transistors and adopts symmetrical magnetically coupled resonators (MCRs) for impedance matching and single-ended differential conversion. Theoretical analysis elucidates the effect of the resonator Q on the frequency response of the transformer, thus giving the distribution of the poles and their precise locations, and revealing the quantitative relationship between bandwidth and gain ripple. A method for efficiently balancing gain ripple and bandwidth in k , Q space under low-power conditions when the intrinsic Q of the source impedance is high is described in detail. Measurement results demonstrate a 51.6% 3-dB bandwidth from 28 to 47.5 GHz. The PA achieve 10.7 dBm P sat , 8.5 dBm OP 1db and 23% peak PAE at 31 GHz. [ABSTRACT FROM AUTHOR]

• Broadband Bi-doped fiber amplifiers are demonstrated. • Optical gain obtained covers O-, E- and S-bands and part of C-band. • The amplification with a focus on the 1310 nm and 1450 nm bands are investigated. • A comprehensive theoretical model for bismuth-doped fiber amplifiers is presented. Optical telecommunications are experiencing an increasing demand for transmission capacity due to the booming internet industry. Expanding the spectral range of communication systems to broader spectral regions beyond the C-band could increase the capacity for optical data transmission. In addition, the development of optical gain medium in E- and S-band is also a major benefit for near-infrared laser therapy. Here, we investigate the optical amplification performance of bismuth-doped fiber amplifiers with different pumping configurations. A broadband amplification from 1280 nm to 1550 nm (O-, E- S- and part of C-band) were demonstrated using bismuth-doped phosphosilicate fibers and low-germanosilicate fibers. The maximum net gains of 18.7 dB and 23.7 dB were obtained in the 1310 nm and 1450 nm regions, respectively, corresponding to noise figures of 5.1 dB and 6.7 dB. Moreover, a comprehensive theoretical model with rate and power propagation equations for bismuth-doped fiber amplifiers is presented to verify the amplifier performance. [ABSTRACT FROM AUTHOR]

In this paper, we propose and demonstrate a hybrid bismuth-doped fiber approach for broadband amplification in the O + E bands. The bismuth-doped fibers were fabricated by the MCVD process combined with solution doping technique. The amplification performance was investigated by the two pump wavelengths of 1240 nm and 1270 nm combined with different pump configurations. The results show that the maximum gain of 38.2 dB with the NF of 3.7 dB was achieved at 1350 nm by the bi-directional pumping configuration. Furthermore, the hybrid bismuth-doped fiber was demonstrated to improve the gain in E-band and maintain the gain flatness between O-band and E-band. A wide bandwidth of ∼150 nm (1310 nm–1460 nm) was achieved by the hybrid fiber, with a gain >15 dB, gain flatness of 8 dB, and NF of 4.1 dB–5.7 dB. [ABSTRACT FROM AUTHOR]

Pr3+/Tm3+/Er3+ tri-doped tellurite glass was synthesised using a melt-quenching method, and the broadband luminescent properties were measured in the near-infrared band. With an optimal combination of the three ions, a broadband luminescence ranging from 1280 to 1630 nm, located within the optical communication window of silica transmission fibre, was acquired under 808 nm excitation. The broadband luminescence comprises three bands: 1.34 μm (Pr3+), 1.47 μm (Tm3+), and 1.53 μm (Er3+); and the full width at half-maximum was about 248 nm. This valuable result is of great significance for novel broadband fibre amplifiers and ultra-short pulsed lasers. [ABSTRACT FROM AUTHOR]

This paper presents a 20-Gb/s automatic gain control (AGC) amplifier in a 0.18-μm SiGe BiCMOS for high-speed applications. The proposed AGC amplifier compactly consists of a folded Gilbert variable-gain amplifier (VGA), a post amplifier (PA), a 50-Ω output buffer, and AGC loop including an open-loop peak detector (PD), a RC low-pass filter (LPF), and an error amplifier (EA). The AGC amplifier achieves the broadband characteristic by utilizing inductive peaking and capacitive degeneration as well as f T -doubler techniques to overcome the large parasitic capacitances. The proposed AGC circuits together with a linear VGA exhibits a wide gain control range of 45 dB for the received signal strength indication (RSSI). The measured AGC amplifier achieves a maximum gain of 21 dB and a -3-dB bandwidth (BW) of 20.6 GHz, which can support up to 25.4-Gb/s data rate. For the pseudorandom bit sequence (PRBS) length 231–1 with a bit-error rate (BER) of 10−12 at 20 Gb/s, the measured input dynamic range is 26 dB (20–400mV pp) and the peak-to-peak data jitter is less than 8 ps. The AGC amplifier consumes a power of 160 mW from a 3.3-V supply voltage and occupies an area of 850 μm × 850 μm. • The proposed 20-Gb/s AGC amplifier consists of VGA, PA, buffer and AGC loop in 0.18-μm SiGe BiCMOS for high-speed link. • Inductive peaking, capacitive degeneration and f T -doubler are utilized to extend the bandwidth (BW). • The proposed AGC circuits together with a linear VGA exhibits a wide gain control range of 45 dB for RSSI. • The measured results show a max gain of 21 dB and a -3-dB BW of 20.6 GHz, a power of 160 mW and an area of 850 μm × 850 μm. • For PRBS31, BER of 10−12 at 20 Gb/s, the measured input dynamic range is 26 dB and the data jitter is less than 8 ps. [ABSTRACT FROM AUTHOR]

In this paper, we present a broadband low-noise amplifier (LNA), using active-feedforward noise-cancellation and complementary n/pMOS configurations. Based on traditional common-gate (CG) and common-source (CS) noise canceling topology, the applied active feedforward stage reduces the CG's dc current and alleviates its resistive load tradeoff between noise and headroom. Meanwhile, the active feedforward stage follows the same noise cancellation (NC) principle as the CG transistors. A low noise figure is thus obtained. In addition, the complementary n/pMOS configuration is used to cancel second-order distortions and double current efficiency. Two π-type matching networks are utilized to broaden the bandwidth of S 11 and gain. After applying these techniques, an LNA prototype was designed in standard 65 nm CMOS technology. Simulation results display a gain of 14–17 dB and a noise figure (NF) of 2.45–3.45 dB within a bandwidth of 1–12 GHz. The linearity of IIP3 and IIP2 are −2.4 and 23 dBm at 5 GHz. The presented circuit consumes only 7.8 mW of dc power while occupying an area of 0.21 mm2. [ABSTRACT FROM AUTHOR]

We report on a series of Er 3 + / Yb 3 + / P 5 + co-doped silica glass from nanoporous silica glass based on glass phase separation technology. The optical properties of the Er 3 + / Yb 3 + / P 5 + co-doped glasses were investigated. Measurements showed that phosphorus can promote energy transfer from Yb 3 + ions to Er 3 + ions while suppressing the energy transfer from Er 3 + ions to Yb 3 + ions and efficiently suppressing the amplified spontaneous emission (ASE) from Yb 3 + ions at 1030 nm. Additionally, the luminescence of Er 3 + ( I 4 13 / 2 → I 4 15 / 2 ) was greatly extended under 976 nm laser excitation, and the full width at half maximum (FWHM) of Er 3 + ( I 4 13 / 2 → I 4 15 / 2 ) was measured to be up to 72 nm and enables the luminescence peak redshifted. The emission cross section of Er 3 + ( I 4 13 / 2 → I 4 15 / 2 ) was calculated to be 1.6 * 10 − 20 cm 2 , one order higher than that of other silica glasses. It is suggested that the Er 3 + / Yb 3 + / P 5 + co-doped silica glasses based on nanoporous silica glass present great potential for broadband amplification. [ABSTRACT FROM AUTHOR]

In this article, ultra-broadband photoluminescence in near-infrared is achieved in KZnF 3 glass ceramics doped with Er3+and Ni2+ ions. Er3+-Ni2+ co-doped fluorosilicate glass and glass ceramics embedded with perovskite nanocrystals were fabricated and efficient energy transfer (ET) from Er3+ to Ni2+ ions was confirmed by luminescence spectra and decay curves. In the glass ceramic samples, Ni2+ ions were effectively sensitized by Er3+, and ultra-broadband photoluminescence from 1400 to 2300 nm was observed when a 980 nm laser was used as a pump, as shown in Fig. 1. The temperature and humidity stability of the glass ceramic samples was characterized from the measured transmittance. These results demonstrated that Ni2+-Er3+ co-doped glass ceramics have significant potential for application in optical communication and broadband amplifiers. [ABSTRACT FROM AUTHOR]

• We present a broadband nanosecond superfluorescent fiber source (ns-SFS). • The impact of the active fiber' s length on the output spectrum of SFS is investigated theoretically and experimentally. • All-fiberized ns-SFS amplifier with average power of greater than 440 W, pulse energy of 17.6 mJ is achieved. In this work, we demonstrate a broadband nanosecond superfluorescent fiber source (ns-SFS) with an average power of several hundred watts and an adjustable repetition frequency of 25 kHz–100 kHz. To figure out a suitable active fiber length for ns-SFS seed, the impact of active fiber length on the output spectrum of SFS is investigated theoretically and experimentally. The results indicate an evident redshift in the central wavelength of output spectrum with increasing fiber length. By scaling the power of the ns-SFS seed employing three amplifier stages, the maximum average power and pulse energy are obtained with a value of 463 W, 17.6 mJ, respectively. To the best of our knowledge, this work is the first demonstration of a broadband ns-SFS amplifier with output power exceeding hundred watt and pulse energy exceeding 10 mJ. [ABSTRACT FROM AUTHOR]

Octahedral CeO 2 :Er3+ nanocrystals were successfully prepared using a simple hydrothermal method, and the structural and excitation dependent emission properties were investigated in detail. Green (2H 11/2 , 4S 3/2 → 4I 15/2), red (4F 9/2 → 4I 15/2) and NIR (4I 11/2 → 4I 15/2 and 4I 13/2 → 4I 15/2) emission were observed under 980 nm laser diode excitation. The optimal Er3+ doping concentration was 3 mol%, and the effect of Li+ co-dopants with concentration up to 10 mol% on microstructure and emission was investigated. However, for the samples excited under 352 nm down-conversion excitation, the Vis-NIR spectral distribution induced distinct changes related to the excitation mode. Remarkably high enhancement of 1532 nm NIR emission about 12 times was achieved by codoping with Li+ ions, which make CeO 2 :Er3+,Li+ nanocrystal a promising candidate for optical amplifier using broadband UV pumping. The possible mechanism of above up-and down-conversion emission and energy transfer process has also been discussed. [ABSTRACT FROM AUTHOR]

Radiation-level 1D 2 adaptive fluorophosphate glasses (NBFP) have been exhibited and relevant transition emissions of Pr3+ have been quantitatively characterized. Intense visible fluorescence is proved to generate from 1D 2 level principally and the quantum yield (QY) of emissions originating from this level is as high as 7.94% in 500–900 nm, indicating the decisive significance of the 1D 2 level in reddish-orange fluorescence of NBFP glasses. Effective broadband 1.47 μm near-infrared (NIR) emission ascribed to 1D 2 →1G 4 transition has been observed, meanwhile, the full-width at half-maximum is obtained to be 141 nm and the maximum stimulated emission cross-section is derived to be 5.75 × 10−21cm2, suggesting the effectiveness of the NIR emission from the initial level 1D 2 in the specific NBFP glasses. In view of absolute radiation parameters and fluorescence branch ratios, net emission photon number of the attractive NIR emission is expected to be 4.5 × 1014cps under 453 nm laser pumping with 82.05 mW power, and corresponding QY is anticipated to be 2.0%. High shortwave transparency and moderate phonon energy are confirmed to be two important indicators for exploring suitable host materials in achieving effective radiations from 1D 2 level of Pr3+, revealing the forward-looking applications of fluorophosphate glasses as broadband NIR amplifiers and irradiative luminescence sources. Image 1 [ABSTRACT FROM AUTHOR]

Abstract A system of zinc fluoride glasses were synthesized to analyse the sensitization mechanism between doped Ln3+ ions under 808 or 980 nm excitation. Differential scanning calorimetry (DSC) curve and Raman spectra indicate the favourable thermal stability and a low maximum phonon energy of the host. Judd-Ofelt (J-O) theory together with the absorption spectra were utilized to compute the Ω t for predicting radiative features of each sample which coincide with the later measured emission spectra. Broadband emission ranging from 2400 to 3300 nm with a half-width of 361 nm in Er3+/Dy3+ codoped zinc fluoride glasses under 980 nm pumping has been investigated, which may be applicated in mid-infrared fiber amplifier and broadband tunable lasers field. On the other hand, the efficient sensitization effect mechanism between Er3+ and Dy3+ around 3 μm band with an extremely high energy transfer efficiency Ƞ (96.1%) of Er3+:4I 13/2 →Dy:6H 11/2 has been researched under 808 nm excitation. Hence, Er3+ and Dy3+ doped zinc fluoride glasses may be potential optical candidates of great development foreground in the fields of mid-infrared applications. [ABSTRACT FROM AUTHOR]

This paper propose an inverted sequential load-modulated balanced amplifier (ISLMBA) for extending the dynamic power range of a power amplifier (PA) over a wide bandwidth. The proposed ISLMBA consists of a control amplifier (CA) and a balanced PA (BPA) pair. A composited impedance inverter is inserted between each BPA transistor and the output coupler. The composited impedance inverter is composed by the intrinsic elements and output matching network (OMN) of the BPA transistor. In this way, the intrinsic elements can be fully absorbed into the impedance inverter over a wide bandwidth. Meanwhile, the load modulation trajectories of the BPA transistors can be optimized over a wide bandwidth by tuning the characteristic impedance of the impedance inverter. The theoretical current, voltage and load-modulation profiles of the ISLMBA are comprehensively analyzed. It is illustrated that the proposed ISLMBA could maintain high efficiency at deep output back-off power level over a wide bandwidth. Moreover, this work designs and fabricates an ISLMBA operating over 1.3–2.55 GHz to verify the proposed PA architecture. The fabricated ISLMBA exhibits a saturation drain efficiency (DE) of 54.5%–73.8% and a saturation output power of 42.9–45.9 dBm. At the same time, the fabricated ISLMBA achieves a 10 dB back-off DE of 42.1%–63.9% over the frequency band of interest. When the fabricated ISLMBA is stimulated by a 20 MHz wideband signal with a peak-to-average power ratio (PAPR) of 10.2 dB at 2.0 GHz, the measured adjacent channel leakage ratios (after predistortion) are −47.7 and −48.8 dBc at the lower and upper bands, respectively. [ABSTRACT FROM AUTHOR]

In this study, Er3+-doped sulfophosphate glasses containing titanium nanoparticles (TiO 2 NPs) with 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05 mol% of silver (Ag) nanoparticles (AgNPs) were synthesized using the melt-quenching technique. The impact of AgNPs on the physical and structural characteristics, optical absorption and emission features, and photocatalytic activity of the glasses were investigated. The density and molar volume of the glasses were determined. Transmission electron microscopy (TEM) was used to study the existence of both AgNPs and TiO 2 NPs in the glass matrix. The absorption spectra of the glasses revealed several bands of absorption in the UV–Vis–NIR region, with peaks at 1534, 977, 795, 650, 544, 520, 487, 450, 406, 378, and 364 nm. The SPR peaks of silver were observed at 553 and 588 nm, while those of TiO 2 NPs were located around 409 and 849 nm. The intensity of emission was found to be enhanced by increasing the concentration of AgNPs. According to the findings of Judd-Ofelt theory, the system containing of 0.04 mol% of AgNPs has also the optimal performance which can be applied to the function of a broadband amplifier by having a high emission cross section of 70.18 × 10−22 cm2. Finally, the photocatalytic performance of the glasses was evaluated by conducting a degradation experiment with methylene blue (MB). The results validated their light-activated self-cleaning properties in the presence of Ag/TiO 2 NPs. • Er3+-sulfophosphate glasses co-embedded with silver and titania nanoparticles were prepared with varying concentrations of silver nanoparticles. • An optimum emission enhancement was observed for the sample containing 0.04 mol% of AgNPs compared to one without. • Spectra of absorption and emission were measured and the J-O theory was applied. • PMZET0.04Ag (70.18 × 10−22 cm2) exhibited the highest emission cross-section associated with the 4F 9/2 → 4I 15/2 transition. [ABSTRACT FROM AUTHOR]

Abstract The peculiarities of transmission and angular non-reciprocity in magneto-photonic crystals (MPC) are investigated. The problem of light transmission through magneto-photonic crystal is solved by Ambartsumian's modified layer addition method. It is shown that the system under consideration can work as a wide band ideal optical diode for orthogonal circular polarizations and as a narrow band ideal optical diode for orthogonal linear polarizations. The influence of the magnitude of external static magnetic field, its direction, and the angle of incidence on the diode properties are investigated. [ABSTRACT FROM AUTHOR]

Abstract A persistent challenge for telecommunications policy is the determination of broadband provision footprints in both space and time. In the United States, Form 477 data from the Federal Communications Commission (FCC) provide a valuable snapshot of broadband provision at the block level, but there are often inconsistencies with the underlying data. These inconsistencies include overly-optimistic self-reports from providers, requirements to report broadband provision within inflexible census administrative units, and a modest temporal reporting schedule (biannual) with a significant, one year temporal lag. These uncertainties are often compounded by telecommunications providers refusing to disclose any information on service footprints, geographic expansion plans or the characteristics of populations served by broadband. This type of obfuscation drastically limits the ability of policy analysts to evaluate outcomes (both positive and negative) associated with service provision and the digital divide, more generally. With the recent entry of Google Fiber to several metropolitan markets in the United States, many of the broadband reporting and evaluation challenges have re-emerged. The purpose of this paper is to leverage basic data mining techniques, a scale agnostic geographic framework and exploratory spatial data analysis (ESDA), to uncover the geographic intricacies of Google Fiber (Fiber) service for both Provo, Utah and Austin, Texas and compare them to Form 477 reports. In addition, we use basic statistical approaches to explore issues of broadband access and equity, accounting for the differences in socio-economic and demographic status of the populace served/not served for both cities, as well as basic pricing within and between communities. Highlights • Information asymmetries for broadband provision data are detailed. • Novel data mining technique is applied to determine the spatial footprint of Google Fiber. • Derived data are compared to FCC Form 477 data. • Google Fiber favors neighborhoods with more renters and impoverished households. • Policy development implications are discussed, focused on closing information asymmetries. [ABSTRACT FROM AUTHOR]

In this work, the near-infrared band photoluminescence properties around 1.0 µm in Pr 3+ /Er 3+ co-doped tellurite glass was investigated. The doped tellurite glass with composition TeO 2 -WO 3 -ZnO-La 2 O 3 was synthesized using melt-quenching technique and characterized by UV/Vis/NIR absorption spectrum, near-infrared emission spectrum, X-ray diffraction (XRD) pattern and Raman spectrum. Under the excitation of 488 nm laser, a broad 1.0 µm band luminescence ranging from 950 to 1100 nm with a full width at half maximum (FWHM) up to 94 nm was observed, nearly two times compared to that in Pr 3+ or Er 3+ single-doped case. This broadband near-infrared luminescence was contributed by the Er 3+ : 4 I 11/2 → 4 I 15/2 and Pr 3+ : 1 D 2 → 3 F 4 radiative transitions which lead to two emissions located at 980 and 1040 nm, respectively. The structural analysis of XRD pattern and Raman spectrum proved the long-range structural disorder in synthesized glasses, and based on the absorption spectrum, some important spectroscopic parameters such as the Judd-Ofelt intensity parameter, spontaneous radiative transition probability, fluorescence branching ratio, absorption and emission cross-sections, and gain coefficient spectrum were calculated to reveal the radiative properties of doped tellurite glass. The obtained results indicate that Pr 3+ /Er 3+ co-doped tellurite glass is a promising candidate to fabricate a broadband near-infrared luminescent source for telecommunication and other applications such as medical imaging system. [ABSTRACT FROM AUTHOR]

Full scale measurement, model testing and a hybrid CFD method were used to characterize the Underwater Radiated Noise (URN) of a ship at design speed. The CFD method consists of a multiphase Delayed Detached Eddy Simulation and the Ffowcs-Williams Hawkings acoustic analogy. The paper discusses the correlation of the noise spectra with the observed cavitation behavior and compares the measured full scale data with those predicted by the model testing and the CFD method. The comparison shows that the sheet cavity and Tip Vortex Cavitation (TVC) predicted by the model testing are in reasonably good agreement with the full scale observations. The pressure pulses are somewhat higher than the full-scale data. Overall, the predicted URN has a good correlation with the noise spectra obtained from the sea trial. The CFD method shows the potential to resolve turbulence eddy structures in the wake. It captures the dynamic development of sheet cavitation and the collapse and rebound of TVC as observed in the model test and the sea trial, but under-predicts the extent of TVC. The pressure pulses and tonal noise are in close agreement with the respective measured data for the first five orders of blade passing frequency. The method underestimates the broadband noise level in the frequency range 50–112 Hz where the TVC is expected to have an important contribution. The maximum under-prediction in this range is about 28 dB at 72 Hz. At frequencies above 200 Hz, the broadband noise becomes more and more under-predicted with increasing frequency. [ABSTRACT FROM AUTHOR]

In this paper, the vibro-acoustic response of a passive earmuff in a broadband frequency range (100 Hz to 5 kHz) is investigated using a finite element analysis. Firstly, the study focuses on the vibro-acoustic response of the cup and the back-plate regardless of the comfort cushion contribution. Secondly, emphasis is put on the foam-filled comfort cushion which is the trickiest component to model because of its physical complexity. This multiphasic cushion is modeled in a simplified way as an equivalent solid, either isotropic or transverse isotropic in order to take into account the added transverse stiffness due to the bulging of the cushion polymeric sheath. The accuracy of these models is investigated by comparing the simulated insertion loss (IL) to measurement data. The IL predicted with the isotropic cushion model is highly underestimated between 500 Hz and 2.5 kHz due to the presence of an unrealistic mode of transverse deformation. It is found that (i) neglecting the acoustic excitation on the cushion’ external flanks of the isotropic model or (ii) using the transverse isotropic cushion model significantly improves the simulated IL. [ABSTRACT FROM AUTHOR]

Er3+-doped Al-Ba-Li phosphate glasses were produced using a melt-quenching method. In the current study, the effect of doping Er3+ ion concentration for photoluminescence efficiency and developing compact optical amplifiers operating at 1.53 μ m was investigated. The optical absorption study reveals that ten absorption peaks, showing highest intensity at 522 nm and 980 nm in UV-Vis and NIR regions, respectively. Mc-Cumber theory was used to conduct and analyse the optical absorption measurements obtained. The maximum intensity was observed at 4I 13/2 → 4I 15/2 transition in the wavelength range of 1400–1700 nm, which is monitored using 980 nm. The highest emission intensity was observed for 1.5 mol% of Er3+ ions doped glass in the NIR emission spectra. The McCumber theory was applied to evaluate the emission cross-sections; for 1.5 mol% of Er3+ ions, the emission cross-section and gain bandwidth value show 9.02 10−21 cm2 and 1.16 1025 cm3 respectively. When the concentration of Er3+ ions increased from 0.1, 0.5, 1.0, 1.5, and 2.0 mol%, respectively, the lifetime () of the 4I 13/2 level reduced from 1.45, 1.19, 0.93, 0.72, and 0.63 ms. The population inversion values show larger than 0.4, suggesting their potential suitability in broadband amplifiers used in C-band communication for a typical population inversion of more than 40%. Phosphate glass doped with Er3+ ions at a concentration of 1.5 mol% doped glass being potential candidate for solid-state optical amplifying devices. [ABSTRACT FROM AUTHOR]

We demonstrate an upscalable approach to increase outcoupling in organic light-emitting diodes (OLEDs) fabricated on flexible substrates. The outcoupling enhancement is enabled by introducing a thin film of microporous polyimide on the backside of silver nanowire (AgNW) electrodes embedded in neat colorless polyimide. This porous polyimide film, prepared by immersion precipitation, utilizes a large index contrast between the polyimide host and randomly distributed air voids, resulting in broadband haze (>75%). In addition, the composite polyimide/AgNW scattering substrate inherits the high thermal (>360 °C), chemical, and mechanical stability of polyimides. The outcoupling efficiency of the composite scattering substrate is studied via optical characterization of the composite substrate and electron microscopy of the scattering film. The flexible scattering substrates compared to glass/indium tin oxide (ITO) allows for a 74% enhancement in external quantum efficiency (EQE) for a phosphorescent green OLED, and 68% EQE enhancement for a phosphorescent white OLED. The outcoupling enhancement remains unharmed after 5000 bending cycles at a 2 mm bending radius. Moreover, the color uniformity over viewing angles is improved, an important feature for lighting applications. [ABSTRACT FROM AUTHOR]

• Nd3+/Tm3+/Er3+ doped tellurite glass was developed using melt-quenching method. • Ultra-broadband flat luminescence of 1300–1630 nm (FWHM = 251 nm) band was obtained. • Ultra-broadband luminescence mechanism and interactions among rare-earth ions were investigated. • The prepared tellurite glass has good thermal stability with Δ T = T x − T g as high as 138 °C. Tellurite glasses doped with Nd3+, Tm3+ and Er3+ ions were synthesized by the melt-quenching technology, and the luminescence property in near-infrared (NIR) band for potential broadband optical communication application was investigated. Pumped at 808 nm laser, an ultra-broadband luminescence between 1300 and 1630 nm, locating at low-loss zone of silica transmission fibers applied in systems of wavelength division multiplexing (WDM), was acquired in the tellurite glass tri-doping of Nd3+/Tm3+/Er3+, which was contributed by the 1.34 µm band of Nd3+, 1.48 µm band of Tm3+ and 1.53 µm band of Er3+. The full width at half maximum (FWHM) of broadband luminescence reaches about 251 nm under the optimal combination of concentrations with 0.025 mol% Nd 2 O 3 , 0.8 mol% Tm 2 O 3 and 0.12 mol% Er 2 O 3. In addition, the difference between the crystallization onset temperature and transition temperature of the studied tellurite glass was approximately 138 °C. The fluorescence decay behavior, spectroscopic and structural characteristics were examined for better understanding the ultra-broadband luminescence. The findings indicates that the tellurite glass tri-doped with Nd3+, Tm3+, and Er3+ ions with good thermal stability is a prospective candidate for tunable fiber lasers and new broadband fiber amplifiers. [ABSTRACT FROM AUTHOR]

• Fine tailoring the surrounding environment of Ni2+ ions to achieve tunable NIR emission. • The value of FWHM of composite exceeds 280 nm, which is a nice result. • This high-performance solid possesses good stability and repeatability. • High level emission and long life make it an excellent candidate material for infrared light sources. ZnGa/AlO 4 provides an octahedral coordination field in which Ni2+ serves as the luminescent center and combines with highly attractive transparent glass ceramics, playing a crucial role in achieving broadband near-infrared (NIR) emission. Transparent glass-ceramics embedded with ZnGa/AlO 4 :Ni2+ mixed crystals prepared by secondary high-temperature melting methods retain the structural characteristics of the dual-phase crystal, which was confirmed by a series of structural and morphological characterization. Through fine tailoring, the surrounding Ni2+ ligand field environment was transformed, realizing special composite NIR emission characteristics with a half-maximum width (FWHM) exceeding 280 nm, which achieved the best results for now in kinds of similar materials. The results show that the NIR emission of ZnGa/AlO 4 :Ni2+-doped transparent glass-ceramics is significantly broadened while maintaining a high level and a long lifetime, which makes it an excellent candidate material for IR light sources and broadband fiber amplifiers. [ABSTRACT FROM AUTHOR]

• A Yb-doped fiber amplifier based on a nonlinear amplifying loop mirror for broadband passive noise suppression and signal amplification. • All polarization-maintaining fiber structure, alignment-free, compact low-noise ultrafast laser amplifier. • The fiber laser system suppressed the amplitude noises from the signal pulses and amplification pump, achieving suppression ratios exceeding 12.7 and 23.0 dB, respectively, with a simultaneous signal amplification ratio reaching 10.0 dB. • The intensity jitter decreased from 0.1 % to 0.03 % (10 Hz–1 MHz) and the phase jitter can be suppressed from 63 to 46 μrad (1 kHz–1 MHz). We investigated the frequency-dependent transfer function of amplitude noise in an all-polarization-maintaining Yb-doped fiber amplifier based on nonlinear amplifying loop mirror (NALM). We generated artificially designed amplitude noise in laser by adding weak sinusoidal modulation into the seed pulses and pump. After transmitting through the NALM-based amplifier, we obtained the amplitude-frequency and phase-frequency responses of the amplitude noise at different gains. Systematic measurements indicate that pump power optimization in the NALM-based amplifier suppresses the amplitude noises from the signal pulses and amplification pump, achieving suppression ratios exceeding 12.7 and 23.0 dB, respectively, with a simultaneous signal amplification ratio reaching 10.0 dB. Moreover, the output noise characteristics confirm that the NALM-based amplifier exhibits broadband amplitude noise and phase noise suppression. Clarifying the mechanism and bandwidth of this amplifier is necessary for low-noise laser generation because it provides insight into the nonlinear laser dynamics of broadband passive noise suppression and signal amplification. [ABSTRACT FROM AUTHOR]

A low-noise (⩽4 fA/√Hz), broadband (⩾100 kHz) compact architecture and related operation solutions are proposed for portable and low-cost time-domain acquisition of currents with effective resolution in the order of 1 pA and below. The front-end architecture is based on an integrating-differentiating scheme to achieve the optimal performance in terms of input-referred equivalent noise, but it overcomes the typical noise/bandwidth trade-off by making the sampling frequency of the A/D conversion independent from the rate at which the analog front-end is reset. In order to strongly mitigate the main drawback, i.e., the introduction in the system of an inherent time-variance, a Track-and-Hold circuit synchronized with the reset is exploited. For validation purposes, a dual-channel prototype was implemented in a low-cost CMOS technology. The prototype is characterized by standard figures of merit and is experimentally validated by two simple case studies, which are typical of practical applications. [ABSTRACT FROM AUTHOR]

In this article, a few-layered graphene-dielectric multilayer (metamaterial) electro-optic modulator has been proposed in the mid and far infrared range that works on electro-absorption mechanism. Graphene, both mono layer and few layer, is an actively tunable optical material that allows control of inter-band and intra-band transition by tuning its chemical potential. Utilizing this unique feature of graphene, we propose a multilayer graphene dielectric stack where few layer graphene is preferred over mono layer graphene. Although the total thickness of the stack still remains in the nanometer range, this device can exhibit superior performances in terms of (i) high modulation depth, (ii) ultra-broadband performance, (iii) ultra-low insertion loss due to inherent metamaterial properties, (iv)nano-scale footprint, (v) polarization independence and (vi) capability of being integrated to a silicon waveguide. Interestingly, these superior performances, achievable by using few layer graphene with carefully designed metamaterial, may not be possible with mono layer graphene. Our proposals have been validated by both the effective medium theory and general transfer matrix method. [ABSTRACT FROM AUTHOR]

An automatic mode low-jitter pulsewidth control loop (PWCL) with enhanced operation frequency is presented in this paper. Using the automatic mode selector (AMS), the proposed PWCL can operate between pulsewidth modulating mode and tracking mode adaptively, avoiding extra power dissipation when a 50% duty cycle input clock is added. Based on the analysis of the delay time between the fixed falling edge and the rising edge generated by PWCL cycle, an auto delay time adjusting delay stage (ADTDS) is proposed to expand the locking frequency range of PWCL. Moreover, an improved charge pump and a novel delay stage are utilized to decrease the supply-induced jitter. The experimental results demonstrate that the proposed PWCL can lock the clock duty cycles for no more than 50±1% with 10–90% input duty cycle from 5 MHz to 750 MHz. At pulsewidth modulating mode, the measurement power dissipation and peak-to-peak jitter are 9.52 mW and 7.72 ps (rising edge) and 9.45 ps (falling edge), respectively, while at tracking mode, 0.6 mW and 10.1 ps achieved with an operating frequency of 750 MHz. The core area of chip is 220 µm×310 µm 2 . [ABSTRACT FROM AUTHOR]

A new type of silver nanoparticles, silver-SiO 2 core-shell nanocubes (Ag NCs@SiO 2 ), is developed for simultaneous broadband absorption and efficient charge collection enhancements in organic solar cells (OSCs), thereby improving short-circuit current density and power conversion efficiency (PCE). The effect of Ag NCs@SiO 2 , present at the bottom of active layer (PTB7:PC 70 BM), on the performance of OSCs were analyzed systematically. The results indicate that the broadband absorption enhancement in the OSCs is realized mainly due to the excitation of the strong localized surface plasmon resonance surrounding the Ag NCs@SiO 2 , supported by the theoretical simulation. While the efficient charge collection efficiency is attributed primarily to the improvement in vertical phase separation of donor/acceptor in the active layer, associated with the process integration of Ag NCs@SiO 2 in the cell fabrication. The use of Ag NCs@SiO 2 benefits the absorption enhancement and also prevents the exciton quenching and carrier charge recombination loss that would occur in cells with pure Ag NCs. The combination of these advantages results in an average PCE of 7.84% for cells with Ag NCs@SiO 2 , corresponding to a 13.6% increase in the efficiency as compared to that of the structurally identical control cell without Ag NCs@SiO 2 . [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) high-index contrast grating (HCG) is proposed as a two-way reflector on Silicon-on-insulator (SOI). The proposed reflector provides high reflectivity over two (practically important) sets of angles of incidence- normal ( θ = 0 ° ) and oblique/grazing ( θ = 80 ° − 85 ° / 90 ° ). Analytical model of 2D HCG is presented using improved Fourier modal method. The vertical incidence is useful for application in VCSEL while oblique/grazing incidence can be utilized in high confinement (HCG mirrors based) hollow waveguides and Bragg reflectors. The proposed two-way reflector also exhibits a large reflection bandwidth (around telecom wavelength) which is an advantage for broadband photonic devices. [ABSTRACT FROM AUTHOR]

The High Luminosity LHC project is aimed at increasing the LHC luminosity by an order of magnitude. One of the key ingredients to achieve the luminosity goal is the beam intensity increase. In order to keep beam instabilities under control and to avoid excessive power losses a careful design of new vacuum chamber components and an improvement of the present LHC impedance model are required. Collimators are among the major impedance contributors. Measurements with beam have revealed that the betatron coherent tune shifts were higher by about a factor of 2 with respect to the theoretical predictions based on the LHC impedance model up to 2012. In that model the resistive wall impedance has been considered as the dominating impedance contribution for collimators. By carefully simulating also their geometric impedance we have contributed to the update of the LHC impedance model, reaching also a better agreement between the measured and simulated betatron tune shifts. During the just ended LHC Long Shutdown I (LSI), TCS/TCT collimators were replaced by new devices embedding BPMs and TT2-111R ferrite blocks. We present here preliminary estimations of their broad-band impedance, showing that an increase of about 20% is expected in the kick factors with respect to previous collimators without BPMs. [ABSTRACT FROM AUTHOR]

Our proposed Optical CDMA network is implemented by spectral-coding of incoherent broadband optical sources. We have utilized the transmissive spectrum characteristics of FBG (Fiber Bragg Grating) to design FBG encoder/decoder. In our design, we have not used any circulator; thereby reducing the cost as well as power loss issue is resolved to a great extent. Signal at the receiver is separated with acceptable bit-error rate ≤10 −9 . The coding and decoding method is based on spectral-amplitude coding of FBG. Here FBG are used to control and modify the amplitude and phase spectrum of broadband incoherent optical signal. The effect of FWM (four wave mixing) is avoided to a larger extent by using this optical CDMA coding technique. Simulation results too confirmed better results in terms of Q factor, SNR and bit error rate in favor of NRZ modulation format compared to other formats. [ABSTRACT FROM AUTHOR]

In this paper, the analytical study of the performance characteristics like group delay, effective mode field diameter (MFD) and dispersion curves of an optical fiber having various cladding layers are presented. The proposed six structures of optical fiber have three parts, namely core with highest refractive index dielectric material, inner claddings and outer cladding. The group delay, MFD and dispersion depend on the number of cladding in optical fiber. The zero dispersion wavelengths vary with number of cladding increases or decreases. The guided modes and propagation wave vectors can be evaluated by using a determinant which is constructed by the boundary matched method. The cutoff conditions of modes for varying number of inner claddings are compared. The analysis shows that the propagation property can be controlled of an optical fiber by increasing the number of inner claddings and diameter of the core. These claddings provide a degree of freedom to control the modes and other characteristics of the fiber. [ABSTRACT FROM AUTHOR]

A compact broadband monolithic microwave integrated circuit (MMIC) sub-harmonic mixer using an OMMIC 70 nm GaAs mHEMT technology is demonstrated for 60 GHz down-converter applications. The present mixer employs an anti-parallel diode pair (APDP) to fulfill a sub-harmonic mixing mechanism. Quasi-lumped components are employed to broaden the operational bandwidth and minimize the chip size to 1.5×0.77 mm 2 . The conversion gain is optimized by a quasi-lumped 90° phase shift stub. Experimental results show that from 50 GHz to 70 GHz, the conversion gain varies between −12.1 dB and −15.2 dB with a LO power level of 10 dBm and 1 GHz IF. The LO-to-RF, LO-to-IF and RF-to-IF isolations are found to be greater than 19.5 dB, 21.3 dB and 25.8 dB, respectively. The second harmonic component of the LO signal is suppressed. The proposed mixer has an input 1 dB compression point of -2 dBm and exhibits outstanding figure-of-merits. [ABSTRACT FROM AUTHOR]

This paper describes the design and analysis of broadband transimpedance amplifiers (TIAs) based on Regulated Cascode (RGC) configuration. The focus is to deal with bandwidth restriction occurring in optical receivers coming from TIA input parasitic capacitances. Despite the conventional method for broadband RGC TIA design that a ladder matching network is employed to isolate the input capacitance of TIA and the photodiode capacitance, the proposed TIA eliminates the effects of these parasitic components by absorbing them in a T-matching network. The conventional broadband RGC TIA is analyzed and the disadvantages of the ladder matching network is demonstrated in a TIA design example. The proposed RGC TIA is simulated on 0.18-μm standard RF CMOS process. The simulation results presented show that the Gain-Bandwidth product (GBW) is extended by a larger factor compared to that of the conventional broadband RGC TIA while the biasing conditions and the value of the photodiode capacitance are considered the same. [ABSTRACT FROM AUTHOR]

Spectroscopic parameters of a novel Nd 3+ -activated barium borate (BBONd) glass have been analyzed for broadband laser amplification. The Judd–Ofelt (JO) intensity parameters were determined through a systematic analysis of the absorption spectrum of Nd 3+ ions in the BBONd glass. High values of the JO intensity parameters reveal a great centro-symmetrical loss of the Nd 3+ sites and high covalency degree of the ligand field. The very high Ω 6 intensity parameter value makes evident both a great structural distortion of the Nd 3+ sites and a strong electron–phonon coupling between Nd 3+ and free OH − ions, which is consistent with the phonon energy maximum (3442.1 cm −1 ) recorded by Raman spectroscopy. This strong electron–phonon coupling favors high effective bandwidth and gain bandwidth values of the laser emission ( 4 F 3/2 → 4 I 11/2 ) of Nd 3+ ions. The electric-dipole oscillator strengths of all the Nd 3+ absorption transitions, and in particular that of the hypersensitive transition ( 4 I 9/2 → 4 G 5/2 ), are enhanced by this great structural distortion of the host. Broadband laser amplification of the 4 F 3/2 → 4 I 11/2 emission (1062 nm) of Nd 3+ ions in the BBONd glass pumped at 805 nm ( 4 I 9/2 → 4 F 5/2 + 2 H 9/2 ) is evaluated through the main fluorescent parameters in competition with non-radiative processes. In general, the BBONd glass exhibits spectroscopic parameters comparable with those reported in the literature for broadband laser amplification into the IR region. [ABSTRACT FROM AUTHOR]

A novel broadband mid-infrared (mid-IR) difference frequency generation (DFG) scheme in a uniform grating periodically poled lithium niobate (PPLN) on the basis of gradient temperature control technique is proposed. Our theoretical results show that the quasi-phase matching bandwidth (BW) for the idler is <10 nm under a fixed crystal temperature condition for two fundamental lights operating in the 1060 and 1550 nm regions. The BW for the idler is remarkably enhanced with increasing temperature gradient across the crystal. When the pump wavelength is fixed at 1.08 μm, the BW for the idler is increased to 18, 40, and 102 nm at 20, 40, and 60 °C, respectively. However, when the signal wavelength is fixed at 1.58 μm, two idler QPM bands for each crystal temperature are achieved. These bands can be simultaneously broadened (in nanometers) to 21 and 14, 54 and 64, and 158 and 161, at 20, 40, and 60 °C, respectively. The broadened idler QPM bands can also be moved over a wide range by adjusting the temperatures at both endfaces of the crystal while maintaining a certain temperature gradient. This scenario is quite useful for further enhancing the mid-IR wavelength coverage. [ABSTRACT FROM AUTHOR]

• Tellurite glass with Er3+/Tm3+/Ag NPs was prepared by melt-quenching method. • Metallic Ag NPs with average size 20 nm were uniformly deposited in glass. • Broadband flat 1350–1650 nm luminescence with FWHM 148 nm was obtained. • Luminescence intensity increased by 81% compared with glass free of Ag NPs. In this study, tellurite glasses co-doped with Er3+/Tm3+ were synthesized through the melt-quenching technique. Under 808 nm excitation, the spectral overlap of 1.53 µm band fluorescence generated by the transition of Er3+:4I 13/2 →4I 15/2 and 1.47 µm band fluorescence generated by the transition of Tm3+:3H 4 →3F 4 achieved the near-infrared (NIR) broadband flat fluorescence emission in the range of 1350–1650 nm, in which the most flat fluorescence emission was achieved when the doping amount of Er 2 O 3 and Tm 2 O 3 was 0.1 and 0.8 mol%, respectively, and the full width at half maximum (FWHM) reached 161 nm. Subsequently, the NIR fluorescence intensity was enhanced by introducing silver nanoparticles (Ag NPs) based on broadband flat fluorescence emission. The optimal conditions conducive to broadband fluorescence enhancement were explored by changing the heat-treated time that could affect the formation and growth of Ag NPs. When the amount of AgCl is 0.5 mol%, tellurite glass co-doped with Er3+/Tm3+ ions heat-treated at temperature 410 ℃ for 6 h has the best enhancement effect of 81 %. After transmission electron microscopy (TEM) measurement, the introduced Ag NPs' diameter at this time is about 18 nm. Some important spectral parameters of Er3+ and Tm3+ ions, for instance the radiative transition probability together with radiative lifetime were calculated from the absorption spectra according to the Judd-Ofelt theory. Structural characteristics based on X-ray diffraction analysis and thermal stability based on differential scanning calorimeter analysis was presented. Based on the above research, the enhanced broadband and flat fluorescence in the 1350–1650 nm range is of great significance for the application of broadband optical amplifiers in modern WDM networks. [ABSTRACT FROM AUTHOR]

• With the introduction of Tm3+, Dy3+ can achieve broadband emission between 2600 and 3400 nm. • The mid-infrared fluorescence intensity enhanced with the increase of Tm3+ due to the energy transfer process between Dy3+ and Tm3+. • Larger absorption and emission cross-sections the glass owned, the gain coefficient was also greatly improved. • The fluorescence lifetime at 2.9 μm were prolonged with the addition of Tm3+. We report the 2600–3400 nm strong mid-infrared (MIR) fluorescence emission with the full width at half maximum (FWHM) of 355 nm in the zirconium fluoride glass incorporated with Dy3+, Tm3+ ions. In this paper, Dy3+, Tm3+ ions co-doped ZrF 4 -BaF 2 -LaF 3 -AlF 3 -YF 3 zirconium fluoride glasses are synthesized by high temperature melting method. Structure information is obtained by raman spectroscopy, and the maximum phonon energy of the synthesized glass is 575 cm−1. Optical performance is mainly characterized by transmission spectrum, absorption spectrum and emission spectrum, theoretical analysis is described by Judd-Ofelt (J-O) theory, cross sections and gain coefficient. Under the 808 nm Laser Diode (LD), the 2.9 μm mid-infrared emission intensity is significantly enhanced with the introduction of Tm3+, and the fluorescence lifetime is prolonged 1.85 ms, the relevant energy transfer mechanism has been further analyzed. All results show that the new glass material may be a potential medium for mid-infrared broadband fiber amplifiers and lasers. [ABSTRACT FROM AUTHOR]

Abstract: Because microperforated panels (MPPs) can provide wide-band sound absorption without fibrous and porous materials, they are recognized as next-generation absorption materials. The fundamental absorbing mechanism is Helmholtz-resonance absorption due to the perforations and air-back cavity. Consequently, MPPs are usually placed in front of rigid-back walls. However, one of the authors has proposed MPP space sound absorbers without backing structures. Among these space absorbers, cylindrical MPP space absorbers and rectangular MPP space absorbers are advantageous due to their design flexibility and easy-to-use properties. Although their performances have been investigated experimentally, it is necessary to predict their absorption characteristics to develop improved shapes and efficient designs. Herein their absorption characteristics are numerically predicted using the two-dimensional boundary element method, and the applicability of a numerical method as a design tool to sufficiently predict the performance of MPP space absorbers is discussed. [Copyright &y& Elsevier]

Abstract: In this paper, the design and implementation of the broadband, Doherty power amplifier (DPA) with 2nd and 3rd harmonics suppression, with theoretical analysis is presented. In the proposed structure a novel harmonic suppressed Wilkinson power divider used in DPA, which results in harmonic suppression with high level of attenuation. Moreover the proposed DPA has major advantages in terms of the linearity and works on a wideband frequency range (2.1–2.7GHz) with minimum 40% drain efficiency (DE). The linearity of the proposed DPA is increased extremely, which significant improvement (7dBm) is achieved from the main amplifier. In the proposed DPA, the main and the auxiliary amplifiers are implemented using Class-AB and Class-C topology respectively with equal MRF6S27015N MOTOROLA transistors in LDMOS technology. [Copyright &y& Elsevier]

Er3+-doped BaNaB glasses with 0.5, 1.0, 2.0, 3.0 and 4.0 mol% of Er3+ were prepared by melt-quenching technique for study their luminescence properties in NIR and visible regions. The absorption spectra showed the absorption bands at 381, 406, 451, 488, 522, 545, 653, 804, 977 and 1532 nm in UV-Vis-NIR region. The NIR emission spectra, excited with 977 nm, show the broad band centered at 1540 nm in the range of 1460–1625 nm covers the S, C and L bands that have low transmission loss region in fiber-optic communication. The glass sample with 3.0 mol% of Er3+ provides the highest intensity of NIR emission. From the Judd-Ofelt analysis and McCumber theory, the glass sample with 4.0 mol% of Er3+ show the best performance for use as a broadband amplifier with the high gain bandwidth at 633.64 × 10−28 cm3 and the high emission cross section at 7.51 × 10−21 cm2. For the emission in visible region, when excited with 349 nm, the glass sample with 3.0 mol% of Er3+ provides the most intense emission in yellow-green region, when excited with 402 nm, the glass sample with 4.0 mol% of Er3+ provides the most intense emission in green region. The results from the McCumber theory and gain efficiency show good agreement of the glass sample with 4.0 mol% of Er3+ for use as broadband amplifier in C and L communication windows when the population inversion is more than 50%. [ABSTRACT FROM AUTHOR]

• Erbium (Er3+) doped Sb 2 O 3 -Na 2 O-WO 3 glasses have been synthesized. • Judd-Ofelt analysis has been used to calculate the radiative transition probabilities (A rad), radiative lifetimes (τ rad), and branching ratios (β). • Broadband emission at 1.53 μm has been obtained under 980 nm laser excitation. • SN0.2WE glass has a minimum W NR value (78.14 s - 1 ) and a maximum quantum efficiency of η = 82.42 % , which is very good compared to other glass hosts. • The emission cross-section and the gain parameter (σ e m a n d F W H M × σ e m ) have considerable bandwidth characteristics higher than other glass hosts. Glasses with compositions (0.8-x)Sb 2 O 3 −0.2Na 2 O-(x)WO 3 -(0.0025) Er 2 O 3 , (0 ≤ x ≤ 0.4 mol) has been synthesized by the melt-quenching technique. Physical, optical characteristics and spectroscopy have been identified and investigated. As the glass composition changes, definite variations in physio-optical properties can be observed as well as the temperature of the glass transition (T g), the density (ρ) , molar volume (V m) , bandgap energy (Eg), and the refractive index (n). The Judd-Ofelt theory has been performed using a UV–VIS-NIR absorption spectrum to examine the compositional effect on Er3+ spectroscopic properties. Some basic spectroscopic parameters including electric dipole line strengths, Judd-Ofelt parameters, the rate of radiative probability, and the lifetime of radiative levels, are determined. A high NIR emission at 1.53 μm was observed when exciting glasses at 980 nm. The FWHM, the effective line-width (Δλ eff), the emission cross-section (σ em), and the gain bandwidth values were calculated using the theory of Füchtbauer–Ladenburg, and the findings were critically analyzed. the decay of fluorescence spectra for the 4I 13/2 level was registered, and the lifetime for the studied glasses was calculated. Upconversion luminescence was observed in the green and red regions under 980 nm excitation, with a relative increase in emission intensity due to the added tungsten content. Based on the results obtained, the studied glasses are favorable materials for broadband amplifiers in WDM systems and optical devices. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic relationship between ICT, income inequality and economic growth in sub-Saharan African (SSA) countries is examined during the period 2004–2014. Three ICT and three income inequality indicators were used to examine this linkage. The ICT indicators used include internet penetration, mobile phone penetration and fixed broadband subscription, while the income inequality indicators include the Gini coefficient, the Atkinson index and the Palma ratio. Using the Generalised Method of Moments (GMM) estimation technique, the study found that, on the whole, an increase in ICT development unconditionally leads to an increase in economic growth in the countries under study. The study also found that the threshold level of income inequality, which should not be exceeded in order for the positive impact of ICT on economic growth to be sustained, depends on the ICT proxy used and the income inequality indicator. Specifically, the study found that for ICT to have a sustained positive impact on economic growth, i) the Gini coefficient in the mobile penetration specification should not exceed 0.520; ii) the Gini coefficient and Atkinson index in the internet penetration specification should not exceed 0.531 and 0.560, respectively; and iii) the Gini coefficient, Atkinson index and Palma ratio in the fixed broadband subscriptions should not exceed 0.551, 0.633 and 4.664, respectively. Policy implications are discussed. • The paper examines the dynamic relationship between ICT, income inequality and economic growth in sub-Saharan African (SSA). • Three ICT and three income inequality indicators were used. • The ICT indicators used include internet penetration, mobile phone penetration and fixed broadband subscription, while the income inequality indicators include the Gini coefficient, the Atkinson index and the Palma ratio. • The study used the Generalised Method of Moments (GMM) to examine this linkage. • The results show that, on the whole, an increase in ICT development unconditionally leads to an increase in economic growth in the countries under study. • The results also show threshold levels of income inequality, which should not be exceeded by the studied countries. [ABSTRACT FROM AUTHOR]