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In this article, a graphene metamaterial based absorber is proposed for controlling and modulating EM waves at terahertz frequency range. Here, we introduced an absorber that can absorb THz radiation over a wide bandwidth of roughly 2.5 THz. The construction of the proposed absorber contains three different layers. In the proposed construction, a silicon layer is used as a dielectric material that separates the graphene patch from the absorber's bottom golden layer. The bandwidth of the proposed absorber can be improved by varying the chemical potential of the graphene material. Compared with the existing literature, the proposed graphene-based metamaterial structure will find numerous potential applications in THz sensing and detecting applications.

Perovskite solar cells (PSCs) have evolved into a viable potential alternative energy source due to their cost-effectiveness and simple fabrication techniques. Despite the immense research interest attracted by PSCs, their rooftop application remains constrained by their low efficiency and hysteretic nature. To address these issues, in this paper, the introduction of silver metallic nanoparticles (AgNPs) with plasmonic effect was achieved by an experimental approach to stimulate the generation and transport of charge carriers, which subsequently results to minimal hysteresis and broadband-enhanced plasmonic devices. Due to the far-field light scattering effect, AgNPs improve the light-trapping of the devices. As a result, electrical characteristics and light absorption are significantly enhanced, leading to broadband increase in photovoltaic performance. With the introduction of one coating cycle of AgNPs, the highest power conversion efficiency (PCE) of the perovskite solar cells increases from a reference value of 4.543 to 10.856%. The fill factor (FF) of such a device was 0.650, the current density (Jsc) was 18.998 mA/cm2, and voltage (Voc) was 0.879 V. This device shows an improvement of ~139.0% in PCE, ~61.7% in FF, ~43.7% in Jsc and ~2.8% in Voc over the pristine device that lacks AgNPs. The findings of this study contribute to further insight and understanding of plasmonic PSCs by offering useful references and recommendations for PSCs with noble metal NPs incorporation. [ABSTRACT FROM AUTHOR]

A series of Mn2+-doped solid Zn3Ga2GeO8 materials with far-red broad-band emissions is prepared as promising candidates for light emitting diodes (LEDs) for application in indoor plant cultivation. Phosphor exhibits broad far-red emissions, ranging from 600 to 1100 nm which overlap with the absorption range of the phytochrome ( P fr ). In addition, the co-doping with Ca2+ contributes a 1.57-fold increase in the far-red-emission intensity at room temperature. Encapsulating phosphor onto ultraviolet LED chips yields far-red-emitting LED devices, which can be promising candidates for promoting indoor plant cultivation. [ABSTRACT FROM AUTHOR]

This paper reports on the preparation of Er3+/Yb3+/Tm3+, Er3+/Yb3+/Nd3+, and Er3+/Tm3+/Nd3+ triply doped and Er3+-doped SiO2-Ta2O5 glass ceramic nanocomposites and active planar waveguides by the sol–gel process using the dip-coating technique as deposition method. The investigation of their structural, morphological, and luminescent properties using XRD, AFM, and photoluminescence analysis, are reported here. The XRD results showed the presence of L-Ta2O5 nanocrystals dispersed in the SiO2-based amorphous host for all the nanocomposites and films. The rare earth ion (RE3+) doping concentration affected both the crystallinity, and the crystallite sizes of the Ta2O5 dispersed into SiO2-Ta2O5 nanocomposites and waveguides. AFM characterization revealed crack free and smooth surface roughness and differences in viscoelasticity on the Er3+-doped SiO2-Ta2O5 films surface, which allows the identification of Ta2O5 nanocrystals on the SiO2 amorphous host. The Er3+ doped and triply doped SiO2-Ta2O5 nanocomposites displayed broad- and super broadband NIR emissions with a FWHM up to 173 nm achieved in the telecom wavelengths. The lifetime of the 4I13/2 emitting level of the Er3+-doped SiO2-Ta2O5 waveguides is strongly dependent on Er3+ concentration and an emission quenching was negligible up to 0.81 mol%. The structural and luminescent investigations indicated that RE3+-doped SiO2-Ta2O5 glass ceramics are promising candidates for photonic applications in optical devices operating in wide wavelengths at the telecom bands.

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering 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.)

Strong absorption, thin thickness, low density and broad band are ideal characteristics of electromagnetic wave absorption (EWA) materials. In this work, ultralight porous carbon hollow nanoboxes (PCHN), which have low density and high specific surface area, are successfully prepared by the vapor deposition and etching process. Excellent EWA performances are achieved in the filler with only 3 wt%. A minimum reflection loss (RL min)value of −30.46 dB (2.2 mm) along with an efficient absorption bandwidth (EAB) (RL ≤ −10 dB) of 5.44 GHz is achieved. And the EAB (RL ≤ −20 dB, corresponding to 99% absorption) can be tuned in the frequency band of 4.88–17.04 GHz via adjusting the thickness from 6.0 to 1.9 mm. The excellent EWA performance is attributed to conduction loss, interfacial polarization, and good impedance matching. Moreover, the adjacent carbon micro-sheets can provide multiple positions for EW reflection, which prolongs the propagation paths of EW and is conducive to the consumption of EW energy. The light weight, broad band and superior RL min value make the as-prepared PCHN promising candidates for practical EWA applications. [ABSTRACT FROM AUTHOR]

Photodetectors with a broad-band response range are widely used in many fields and are regarded as pivotal components of the modern miniaturized electronics industry. However, commercial broad-band photodetectors composed of traditional bulk semiconductor materials are still limited by complex preparation techniques, high costs, and a lack of mechanical strength and flexibility, which are difficult to satisfy the increasing demand for flexible and wearable optoelectronics. Therefore, researchers have been devoted to finding new strategies to obtain flexible, stable, and high-performance broad-band photodetectors. In this work, a novel self-assembled BiGaSeAs composite superlattice-structured nanowire was developed with a simple chemical vapor deposition method for easy fabrication. After the device assembling, the photodetector showed outstanding performance in terms of obvious I on / I off (13.9), broad-band photoresponse (365-940 nm), excellent responsivity (1007.67 A/W), high detectivity (9.38 × 10 9 Jones), and rapid response (21 and 23 ms). The formation of microheterojunctions among various materials inside the nanowires also contributed to their extended broad-spectrum response and outstanding detection ability. These results indicate that the BiGaSeAs nanowires have potential applications in the field of flexible and wearable electronics.

Broadband sources of near-infrared (NIR) radiation have garnered considerable attention in medical applications and non-destructive analysis. In this work, we have synthesized a lithium zinc stannate phosphor Li1.6Zn1.6Sn2.8O8:Cr3+ (LZSO:Cr) for broadband NIR light sources. The LZSO:Cr phosphor exhibited broadband excitation band matches exceptionally well with the emission of commercial 450-nm blue light-emitting diode (LED) chips. As expected, the broadband emission of infrared radiation from 650 nm to 1200 nm was realized due to the unique crystal field environment, where Cr3+ ions were substituted in two distorted octahedral sites. The broad emission spectrum exhibited peaks around 830 nm and 930 nm with a full width at half maximum (FWHM) of ~190 nm and internal quantum efficiency of 53%. The FWHM could be tuned to ~220 nm by co-doping with Al3+ ions because of the crystal splitting. The luminescence properties including excitation, emission, decay time, and their relationship between the lattice crystal properties have also been investigated. A phosphor-converted LED (pc-LED) was packaged by combining the phosphor with a 450-nm blue LED chip, which proves the feasibility of our design strategy for broadband NIR light sources.

Energy harvesting methods that use functional materials have attracted interest because they can take advantage of an abundant but underutilized energy source. Most vibration energy harvester designs operate most effectively around their resonant frequency. However, in practice, the frequency band for ambient vibrational energy is typically broad. The development of technologies for broadband energy harvesting is therefore desirable. The authors previously proposed an energy harvester, called a flexible piezoelectric device (FPED), that consists of a piezoelectric film (polyvinylidene difluoride) and a soft material, such as silicon rubber or polyethylene terephthalate. The authors also proposed a system based on FPEDs for broadband energy harvesting. The system consisted of cantilevered FPEDs, with each FPED connected via a spring. Simply supported FPEDs also have potential for broadband energy harvesting, and here, a theoretical evaluation method is proposed for such a system. Experiments are conducted to validate the derived model. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic 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.)

In this letter, a broadband high-gain circularly polarized Fabry-Perot resonator antenna (CP-FPRA) with simple array thinning technique is proposed. The proposed antenna consists of a single layer partially reflective surface (PRS) formed by ring frequency selective surface (FSS) and a four sequential rotated sparse primary microstrip patch radiators backed with ground. The inter-spacing of adjacent primary radiator is around 1 λ0, which is larger than the typical value of 0.5 λ0 in microstrip patch array. A prototype antenna operating at 10 GHz is designed. Simulated and experimental results show that a broad common bandwidth for | S11| ≤ −10 dB and gain-drop ≤2 dB and axial ratio ≤3 dB is obtained, in which the good CP radiation properties such as high gain, low side lobe level are also proposed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department 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.)

Electromagnetically induced transparency-like (EIT-like) and electromagnetically induced absorption-like (EIA-like) can be easily generated separately in metastructure (MS), but it is rare to achieve both states simultaneously in a single device, let alone broadband EIT-like and EIA-like. Notably, the responses of the left-handed circularly polarized waves and the right-handed circularly polarized waves to the MS are the same, demonstrating the generation of polarization-insensitive EIT-like and EIA-like. The photosensitive silicon (Si) is chosen to control the state of the device, realizing the mutual conversion between EIT-like and EIA-like. With the incidence of circularly polarized (CP) waves, the broadband EIT-like can be observed between 0.505 THz and 1.403 THz, where the maximum group delay and group index can arrive at 1.57 ps and 7.26, respectively. Besides, the transition from broadband EIT-like to broadband EIA-like can be successfully achieved in the same frequency band when Si is excited by the pump light, where Si-based ladder structure (SBLS) is adapted to enhance absorption efficiency to realize broadband EIA-like. The relative bandwidths of EIT-like and EIA-like have reached 26.5% and 15.2%, respectively. The theoretical RLC (resistance, inductance, and capacitance) equivalent circuit model demonstrates the feasibility of broadband EIT-like and EIA-like implementation. • Transition between EIT-like and EIA-like can be controlled by pump light. • The photosensitive material silicon is utilized in the paper. • The relative bandwidth of both EIT-like and EIA-like behaviors exceeds 15%. • The presented structure adopts circular polarization incidence. • Both EIT-like and EIA-like phenomena are polarization insensitive. [ABSTRACT FROM AUTHOR]

Wide-band circularly polarized multi-input multi-output (MIMO) antenna array with a 2 × 4 feed network was proposed for C-band application. Different unique techniques were utilized in the proposed array to enhance the antenna characteristics, such as gain, 3 dB axial ratio bandwidth (ARBW), impedance tuning, and ruinous mutual coupling effects. A miniaturized dual-feed Tai chi-shaped antenna element with a pair of feeding points and a pair of eyebrow-shaped strips was presented for enhancing circular polarization (CP) purity and impedance matching. For a better improvement of CP features, a 2*4 MIMO sequentially rotated (MIMO-SR) feed network was used to achieve broader 3 dB ARBW. Besides, the MIMO feature of the feed network could control the left- and right-handed CP, respectively. Ultimately, specific forms of slot and slit structures were applied onto the top layer of MIMO feed network that provided a high isolation between the radiating elements and array network. Furthermore, the diversity gain (DG) was studied. The extracted measured results illustrated an impedance bandwidth of 3.5–8.2 GHz at port 1 and 3.5–8.3 GHz at port 2 for VWSR < 2 and 3 dB ARBW of 4.6–7.6 GHz at port 1 and 4.6–7.5 GHz at port 2. The peak gain of 9.9 dBi was at 6 GHz. [ABSTRACT FROM PUBLISHER]

This paper reports a non-resonant, broadband electromagnetic vibration-energy harvester based on self-assembled ferrofluid liquid bearing. Magnet array is suspended by the liquid bearing over a microfabricated multi-layer coil plate such that the energy harvester does not rely on any mechanical resonance, and can harvest vibration energy over a broad frequency range. An analytical model of the non-resonant energy harvester with liquid bearing is developed to predict the frequency responses under various external accelerations. Experimental results show that the electromagnetic energy harvester occupying 1.1 cm3 and weighing 2.5 gram generates an induced electromotive force of \textV\mathrm {rms} =61 to 93.7 mV (delivering 11.6– 27.5~\mu \textW power into 80- $\Omega $ load) from 2-g acceleration at 2–4 Hz. When the energy harvester is placed on the back of a human walking at various speeds, the power output is increased as the walking speed is increased from 0.44 m/s (walking) to 3.56 m/s (running), and reaches 18.1~\mu \text{W} at 3.56 m/s. [2016-0167] [ABSTRACT FROM PUBLISHER]