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- 2018
- GaN HEMTs
- Power amplifier
- Broadband power amplifier
- SC band
- Power combining
- concentrated capacitive load
- distribution of the complex current at the antenna
- broadband antenna
- standing wave voltage factor
- antenna gain factor
- Electronic Science and Technology
- Oles Honchar Dnipro National University
- University of Tehran
- Gdansk University of Technology
- V. N. Karazin Kharkiv National University
- Reykjavik University
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Nano-plasmonic Bundt Optenna for broadband polarization-insensitive and enhanced infrared detection
摘要： Infrared detection devices are becoming miniature with micro or nano-scale size. The advantages of downsizing come on the expense of insufficient collection of infrared radiation. Therefore, utilizing nano-plasmonic optical antennas becomes mandatory. However, it is desirable to develop antennas with broad bandwidth, polarization insensitivity, wide field-of-view, and reasonable plasmonic losses in order to collect most of incident infrared radiation and enhance power absorption efficiency. Here, an innovative optical antenna (optenna) is proposed and demonstrated for the first time. It has a novel shape of Bundt baking-pan. The gold Bundt is arranged in a periodic array that can be placed on top of a thin-film infrared absorbing layer. The developed optenna can squeeze infrared electric and magnetic fields to 50 nm-wide area in order to enhance material absorption efficiency. It demonstrates polarization insensitivity and ultra-broad bandwidth with a large fractional-bandwidth within the near, shortwave, and midwave infrared bands. It shows a remarkable enhanced power absorption efficiency up to 8 orders of magnitude with a reasonable average power loss of ?3 dB and 80° field-of-view. It can be promising for future applications in solar-cells, telecommunication photodetectors, shortwave cameras, and midwave microbolometers.
关键词： optical antenna,infrared detection,polarization-insensitive,broadband,nano-plasmonic
更新于2025-09-11 14:15:04
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Hysteretic behavior in ion gel-graphene hybrid terahertz modulator
摘要： A polarization-reconfigurable and frequency-tunable mechanism based on an active artificial magnetic conductor (AMC) structure is proposed. The active AMC unit cell consists of a four-corner-cut inner patch and four triangles loaded with four varactors, and it can realize polarization-reconfigurable and frequency-tunable reflection characteristics by adjusting the capacitance of the varactors. By employing it as a ground plane of a pair of linearly-polarized dipole antennas, a multi-functional antenna can be well designed with polarization reconfigurability and frequency-tuning capability. By controlling the DC bias of the varactors accordingly, the three polarization states of right-/left-handed circular polarization (R/LHCP) and linear polarization (LP) can be switched, respectively, while the operating frequency of each polarization can be flexibly tuned. The measured tuning frequency ratio for the LP state (|S11| < ?10dB) can reach 1.56:1, while the ratio for either the LHCP or RHCP state (axial ratio< 3dB) is about 1.28:1. Moreover, a large bandwidth for each polarization state can be obtained, where the bandwidths are up to 17.1% and 8.7%, respectively, for the LP and CP states. Besides, it is more flexible for the CP states since the bandwidth can be adjusted. For a demonstration, one prototype of the proposed antenna is fabricated and measured. The agreement between the theoretical and measured results indicates good performances of the proposed antenna.
关键词： Artificial magnetic conductor (AMC),multi-functional antenna,frequency-tunable,broadband,polarization-reconfigurable
更新于2025-09-11 14:15:04
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A broadband terahertz metamaterial absorber enabled by the simple design of a rectangular-shaped resonator with an elongated slot
摘要： Broadband metamaterial absorbers are of critical importance in practical applications, but their obtainment approaches are quite complex at present. We demonstrate here that a fairly simple structure design formed by a rectangular-shaped resonator having an elongated slot can be utilized to achieve a broadband absorption response at terahertz frequencies. More than 50% absorption in a continuous frequency range of 1.62 THz (with a central frequency of 2.05 THz) can be gained, and its relative absorption bandwidth is 79.02%, which is superior to that of previous broadband absorption devices. The basic principle of the broadband absorption originates from the superposition of four di?erent but narrowly separated resonance peaks that resulted from di?erent response positions of the suggested resonator. Results further reveal that the broadband terahertz absorption performance (or its four resonance peaks) can be controlled by the resonator dimensions. The suggested method can provide a new type of design strategy to realize broadband integrated terahertz absorption devices.
关键词： resonance peaks,rectangular-shaped resonator,elongated slot,broadband metamaterial absorbers,terahertz frequencies
更新于2025-09-11 14:15:04
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Study on Detecting Dielectric Properties of Typical Electrical Insulation Materials by Terahertz Wave Spectroscopy
摘要： The dielectric properties of the electrical insulation materials is of great importance to the safe operation of the power system. As a promising technique in the field of material testing and with the very adaptive physical modeling of wave transmission process, terahertz wave was used to measure the dielectric properties of five commonly used insulation materials by two methods in this paper. When excluding the echo pulse from the reference signal and the sample signal, a better signal-noise ratio and a wider effective frequency band of spectrums can be obtained. Alternatively, the dielectric properties can also be achieved by separating the main pulse and echo pulse from the sample signal. The latter method makes the sampling of reference signal unnecessary. Furthermore, the dielectric properties of materials were also measured on a relative lower frequency band (1Hz-1MHz) by the broadband dielectric spectrometer. Compared with a relatively lower frequency band, due to the polarization, the dielectric constant of the tested insulation materials was lower on the terahertz band while the dielectric loss tangent was generally higher except the epoxy resin.
关键词： Dielectric properties,Terahertz wave,Insulation materials,Broadband dielectric spectrometer
更新于2025-09-11 14:15:04
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Graphene-embedded broadband tunable metamaterial absorber in terahertz band
摘要： Numerous studies have been conducted to design terahertz broadband metamaterial absorbers for various applications such as electromagnetic stealth, photodetection, and broadband communications. And it remains a hot research topic to design metamaterial absorber (MA) to achieve broadband absorption while maintaining a wide range of tunability. Here, we present a novel design of graphene-embedded metamaterial functioning as a broadband tunable absorber based on the field reinforcement effect and plasmon resonance of graphene. With a stacked configuration, the absorptivity of the MA proposed in this paper can be as high as 90% in a wide range of 1.2 THz. By comparative analysis, we exhibit that the MA shows a relatively wider absorption bandwidth than the one without the embedded graphene, which discloses the significance of integrating graphene layer in our design. The detailed numerical calculations of the surface currents and electric field distributions are presented in this paper to better uncover the physical mechanisms of the broadband and multi-band absorption. Moreover, further numerical calculations show that the designed MA also demonstrates several other excellent properties such as tunability, polarization insensitivity, incident angle insensitivity and outstanding structural parameters tolerance. The proposed graphene-embedded MA can be used in various promising applications, like smart sensors, broadband absorber and imaging devices.
关键词： insensitivity,field reinforcement effect,tunability,plasmon resonance,metamaterial absorber,broadband,graphene
更新于2025-09-11 14:15:04
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Broadband γ-graphyne saturable absorber for Q-switched solid-state laser
摘要： γ‐graphyne, as a member of two‐dimensional carbon materials, has attracted much attentions benefitting from its unique characteristics, such as high carriers mobility, high stability, etc. In the present study, a γ‐graphyne saturable absorber (SA) was fabricated and characterized. The linear optical absorption in the spectral range from the visible to mid‐infrared as well as the nonlinear optical character of the SA were investigated. The passively Q‐switched solid‐ state lasers emitting at 639 nm, 1342 nm, 1932 nm were realized by using the γ‐graphyne SA. The results indicate that the γ‐graphyne could be a promising alternative for rare broadband optical modulator.
关键词： broadband optical modulator,saturable absorber,solid‐state laser,Q‐switched,γ‐graphyne
更新于2025-09-11 14:15:04
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Charge Transport Behavior and Ultrasensitive Photoresponse Performance of Exfoliated F <sub/>16</sub> CuPc Nanoflakes
摘要： Air-stable, photosensitive copper hexadecafluorophthalocyanine (F16CuPc) is a promising n-type semiconductor for organic electronics and optoelectronics. However, the performance of F16CuPc-based devices is significantly limited by the poor crystallinity of thin films. Here, the charge transport and electrical contact behavior of F16CuPc nanoflakes, mechanically exfoliated from needle-like bulk single crystals, are probed by analyzing the temperature-dependent carrier mobility and conductance, where the multiple-trap/release- and band-like transport mechanism govern the charge transport at different temperature ranges and carrier densities. F16CuPc nanoflake-based field effect transistors (FETs) exhibit high on-state current and ON/OFF ratio, one-order magnitude higher than those of reported F16CuPc nanowires, thin films, and nanoribbons. Besides, F16CuPc nanoflake-based phototransistors exhibit attractive photoresponse performance in the spectral range of 300–750 nm even at quite low operating source–drain voltage (1 V), with maximum photoresponsivity of 19 A W?1, detectivity of 8 × 1012 Jones, and fast response speed of 36 ms, which is attributed to the single-crystalline characteristic of nanoflakes, and the resultant efficiently exciton diffusion and charge transport. The work demonstrates that 2D organic nanoflakes with single-crystalline feature will be promising candidates for flexible electronic and optoelectronic devices.
关键词： organic phototransistors,broadband photoresponse,charge transport,F16CuPc nanoflakes
更新于2025-09-11 14:15:04
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Nanoplasmonics Enhanced Broadband Ultra-Sensitive Mid-Ir Sensor Array Integrated with Microfluidics
摘要： This paper shows a broadband ultra-sensitive IR sensor with novel folded gold nanoantenna sensing array on CaF2 substrate integrated with microfluidic channel, which will allow, for the first time, continuous monitoring wideband finger print IR absorption of liquid and solution using enhancement of plasmonic nanoantenna. The broadband detection window we achieve is over 10 times larger than single nanorod antenna array, which pave the way to real-time fingerprint monitoring and various molecular recognition.
关键词： broadband IR sensor array,dynamic spectroscopy,nanoantennas,infrared surface-enhanced monitoring,plasmonic
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE MTT-S International Microwave and RF Conference (IMaRC) - Kolkata, India (2018.11.28-2018.11.30)] 2018 IEEE MTT-S International Microwave and RF Conference (IMaRC) - A Graphene Based Metasurface with Wideband Absorption in the Lower Mid Infrared Region
摘要： An ultra-thin (~λ/34) graphene based metasurface exhibiting wide bandwidth in lower mid-infrared region has been discussed in this paper. The unit cell of the structure composes of graphene-based fractal geometry on the top surface depicted over amorphous silicon dioxide (SiO2) whose bottom side is completely graphene deposited. The geometrical dimensions of the deposited graphene pattern are chosen so that broadband absorption is achieved between 1.75 THz and 7.28 THz with more than 90% absorptivity. Two distinct absorption peaks have also been observed at 3 THz and 7 THz in the aforementioned broad absorption spectra. The designed prototype has been observed under different incident angles of the incoming electromagnetic wave for both TE and TM polarizations where bandwidth improved absorption has been observed upto 60o incident angles for both cases. The structure is also found to be polarization independent in nature.
关键词： polarization-insensitive,absorber,Metasurfaces,broadband,graphene
更新于2025-09-11 14:15:04
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High-performance nitrogen doped carbon quantum dots: Facile green synthesis from waste paper and broadband photodetection by coupling with ZnO nanorods
摘要： High-performance N-doped carbon quantum dots (NCQDs) were synthesized by a proposed green route based on hydrothermal treatments using waste paper and urea as C and N sources. The single-crystalline NCQDs demonstrated strong blue-green luminescence with the maximum intensity enhancement of 6.5 times when compared with undoped CQDs under UV and visible light excitations. XPS spectra results suggested that the enhanced photoluminescence might be attributed to pyridinic N, which could be controlled by adjusting hydrothermal temperature, time, and urea concentration. The NCQDs having excellent optoelectronic properties were fabricated into broadband photodetectors by incorporating ZnO nanorod arrays. Owing to the NCQDs, the detectors demonstrated broadband photoresponse with significantly enhanced photoresponsivity, faster response, and better sensitivity in visible range. The work provides a low-cost, environment friendly route to fabricate excellent NCQD-based broadband photodetectors for various technological applications.
关键词： Photodetection,ZnO,Broadband,Nitrogen,Carbon quantum dot
更新于2025-09-11 14:15:04