Response Bandwidth Research Articles

Black Arsenic Phosphorus Mid-Wave Infrared Barrier Detector with High Detectivity at Room Temperature.

The barrier structure is designed to enhance the operating temperature of the infrared detector, thereby improving the efficiency of collecting photogenerated carriers and reducing dark current generation, without suppressing the photocurrent. However, the development of barrier detectors using conventional materials is limited due to the strict requirements for lattice and band matching. In this study, a high-performance unipolar barrier detector is designed utilizing a black arsenic phosphorus/molybdenum disulfide/black phosphorus van der Waals heterojunction. The device exhibits a broad response bandwidth ranging from visible light to mid-wave infrared (520nm to 4.6 µm), with a blackbody detectivity of 2.7× 1010 cmHz-1/2 W-1 in the mid-wave infrared range at room temperature. Moreover, the optical absorption anisotropy of black arsenic phosphorus enables polarization resolution detection, achieving a polarization extinction ratio of 35.5 at 4.6 µm. Mid-wave infrared imaging of the device is successfully demonstrated at room temperature, highlighting the significant potential of barrier devices based on van der Waals heterojunctions in mid-wave infrared detection.

Giant electric field-induced second harmonic generation in polar skyrmions

Electric field-induced second harmonic generation allows electrically controlling nonlinear light-matter interactions crucial for emerging integrated photonics applications. Despite its wide presence in materials, the figures-of-merit of electric field-induced second harmonic generation are yet to be elevated to enable novel device functionalities. Here, we show that the polar skyrmions, a topological phase spontaneously formed in PbTiO3/SrTiO3 ferroelectric superlattices, exhibit a high comprehensive electric field-induced second harmonic generation performance. The second-order nonlinear susceptibility and modulation depth, measured under non-resonant 800 nm excitation, reach ~54.2 pm V−1 and ~664% V−1, respectively, and high response bandwidth (higher than 10 MHz), wide operating temperature range (up to ~400 K) and good fatigue resistance (>1010 cycles) are also demonstrated. Through combined in-situ experiments and phase-field simulations, we establish the microscopic links between the exotic polarization configuration and field-induced transition paths of the skyrmions and their electric field-induced second harmonic generation response. Our study not only presents a highly competitive thin-film material ready for constructing on-chip devices, but opens up new avenues of utilizing topological polar structures in the fields of photonics and optoelectronics.

Iontronic Dynamic Sensor with Broad Bandwidth and Flat Frequency Response Using Controlled Preloading Strategy.

Rapid advancements in human-machine interaction and voice biometrics impose desirability on soft mechanical sensors for sensing complex dynamic signals. However, existing soft mechanical sensors mainly concern quasi-static signals such as pressure and pulsation for health monitoring, limiting their applications in emerging wearable electronics. Here, we propose a hydrogel-based soft mechanical sensor that enables recording a wide range of dynamic signals relevant to humans by combining a preloading design strategy and iontronic sensing mechanism. The proposed sensor offers a two-orders-of-magnitude larger working bandwidth (up to 1000 Hz) than most of the reported soft mechanical sensors and meanwhile provides a high sensitivity (-23 dB) that surpasses the common commercial microphone. The amplitude-frequency characteristic of the proposed sensor can be precisely tuned to meet the desired requirement by adjusting the preloads and the parameters of the microstructured hydrogel. The sensor is capable of recording instrumental sounds with high fidelity from simple pure tones to melodic songs. Demonstration of a skin-mountable sensor used for human-voice-based remote control of a toy car shows great potential for applications in the voice user interface of human-machine interactions.

Operation of kinetic-inductance travelling wave parametric amplifiers at millimetre wavelengths

It is expected that the operation of microwave kinetic inductance travelling wave parametric amplifiers (KITWPAs) can be extended to the millimetre (mm) and the sub-mm wavelength range as long as the frequency is below the gap frequency of the superconducting film. This paper presents possible mm-wave designs for KITWPAs based on microstrip transmission lines. Our device is designed based on the BCS (Bardeen–Cooper–Schrieffer) model which successfully reproduces the measured transmission profile, gain, bandwidth, and nonlinear response of a fabricated KITWPA operating in the Ka-band, and includes the millimetre-wave dielectric loss determined by fitting the quality factor of a W-band microstrip resonator. We suggest a layout for a KITWPA operating near 220 GHz that can be fabricated using the same superconducting properties as the Ka-band device and can be coupled to a waveguide system. We conclude the paper by extending the 220 GHz design to higher frequency regimes approaching 1 THz.

Observation of Wide Bandwidth and Giant Chiroptical Response Empowered by Core–Shell Micro‐Helixes

Helical microstructures exhibit unprecedented chiroptical responses particularly interesting for emerging applications such as broadband photonic components. To explore their chiral behaviors, the micro‐helixes composed of polymer cores and platinum shells are proposed and realized via a two‐step process combining two‐photon polymerizations and sputter coating. Thanks to the core–shell multi‐material configurations, the micro‐helixes packed in a dense array generate an ideal chiral lineshape. Overspanning a wide range from 3 to 7 μm, the reflection‐based g factors approach the upper amplitude limits. Numerical modeling reveals that polarization‐induced spectra result from overlapping modes similar to the previously reported solid metal helixes. The further chiral spectrum comparisons confirm that the core–shell spirals exhibit a 25% bandwidth increase compared to solid platinum helixes of same sizes. Interestingly, the asymmetrically distributed platinum shell may further expand the operational band. Overall, comprehensive studies are performed on multi‐material micro‐helixes, which could provide additional flexibility to tailor their chiroptical properties, enabling the production of high‐performance chiral microstructures for diverse applications.

Polarization-independent wideband meta-material absorber based on resistor-loaded hexagonal ring resonators

A polarization-independent meta-material-based absorber with wideband response is presented in this study. The proposed absorber’s unit cell consists of a resistance-loaded metallic hexagonal ring and four rectangular metal strips placed inside the hexagonal ring patterned on the upper surface of a dielectric substrate. The absorber exhibits wideband absorption with absorptivity more than 90% in the frequency range 7.14 to 13.68 GHz. The Full-Width Half Maxima (FWHM) of the absorber is 8.8 GHz (5.2–14 GHz). The four-fold symmetrical structure of the absorber confirms polarization-insensitive behaviour. The absorber performance is also validated with fabrication and measurement. There is a fair degree of agreement between simulated and measured results. The novelty of the proposed absorber is having wideband absorption with high packing density due to its hexagonal shape. The metamaterial absorber finds its use in defence-related applications such as radar surveillance, stealth technology, terrestrial communications, and satellite communication.

Compact designs of circular microstrip antennas employing modified ground plane for wideband response

Wideband Compact designs of circular microstrip antennas by employing modified ground plane profile are proposed. Ground plane slots reduces patch fundamental mode frequency and Bow-tie shape of the same yields wider bandwidth on thinner substrate, thus achieving wider bandwidth with a smaller antenna volume. Optimum results are achieved using three rectangular slots cut Bow-tie shape ground plane. Against the conventional ground plane design, modified ground plane antenna yields 25% bandwidth increment, 0.03λg reduction in substrate thickness, 35.12% reduction in the resonance frequency, 66% reduction in the patch area with a broadside peak gain of 5.5 dBi. Reported wideband configurations do not provide bandwidth enhancement with a patch size reduction, and thus this is the novelty in the proposed work. Simulated results are have been experimentally verified that shows close agreement.

Single-wideband and dual-band bandpass filters based on compact quadruple-mode resonator

A stub-loaded U-shaped microstrip resonator (U-SLR) exciting two odd-modes and two even-modes and its applications to single-wideband and dual-band bandpass filter (DB-BPF) are introduced. The parallel-coupled lines (PCLs) at input/output (I/O) ports can provide a wideband response by exciting two additional modes in the passband, so-called PCLs modes. In addition to the transmission poles (TPs) in the passband, two transmission zeros (TZs) in the lower and upper stopbands can be created by the loaded stubs. A compact size, high-selectivity, and low insertion loss WB-BPF is designed, fabricated, and tested. Moreover, a compact and low loss DB-BPF with closely spaced passbands is designed and tested. TZ-shifting method is used to design a DB-BPF by splitting the wideband. To achieve this, it is sufficient to change the length of only one of the loaded stubs. The calculated, simulated and measured frequency responses for both single-wideband and DB-BPFs are in very good agreement.

Light-Emitting Plasmonic Tunneling Junctions: Current Status and Perspectives.

Quantum tunneling, in which electrons can tunnel through a finite potential barrier while simultaneously interacting with other matter excitation, is one of the most fascinating phenomena without classical correspondence. In an extremely thin metallic nanogap, the deep-subwavelength-confined plasmon modes can be directly excited by the inelastically tunneling electrons driven by an externally applied voltage. Light emission via inelastic tunneling possesses a great potential application for next-generation light sources, with great superiority of ultracompact integration, large bandwidth, and ultrafast response. In this Perspective, we first briefly introduce the mechanism of plasmon generation in the inelastic electron tunneling process. Then the state of the art in plasmonic tunneling junctions will be reviewed, particularly emphasizing efficiency improvement, precise construction, active control, and electrically driven optical antenna integration. Ultimately, we forecast some promising and critical prospects that require further investigation.

Reconfigurable Designs of Sectoral Microstrip Antennas for Wideband and Circularly Polarized Response

Reconfigurable Designs of Sectoral Microstrip Antennas for Wideband and Circularly Polarized Response

Double-cliff-layer uni-traveling-carrier photodiode with high responsivity and ultra-broad bandwidth

Double-cliff-layer uni-traveling-carrier photodiode with high responsivity and ultra-broad bandwidth

Multi Resonant Gap-coupled Designs of E-shape Microstrip Antenna for Wideband Response

Multi Resonant Gap-coupled Designs of E-shape Microstrip Antenna for Wideband Response

Integrated Distributed Sensing and Quantum Communication Networks.

The integration of sensing and communication can achieve ubiquitous sensing while enabling ubiquitous communication. Within the gradually improving global communication, the integrated sensing and communication system based on optical fibers can accomplish various functionalities, such as urban structure imaging, seismic wave detection, and pipeline safety monitoring. With the development of quantum communication, quantum networks based on optical fiber are gradually being established. In this paper, we propose an integrated sensing and quantum network (ISAQN) scheme, which can achieve secure key distribution among multiple nodes and distributed sensing under the standard quantum limit. The continuous variables quantum key distribution protocol and the round-trip multiband structure are adopted to achieve the multinode secure key distribution. Meanwhile, the spectrum phase monitoring protocol is proposed to realize distributed sensing. It determines which node is vibrating by monitoring the frequency spectrum and restores the vibration waveform by monitoring the phase change. The scheme is experimentally demonstrated by simulating the vibration in a star structure network. Experimental results indicate that this multiuser quantum network can achieve a secret key rate of approximately 0.7 Mbits/s for each user under 10-km standard fiber transmission, and its network capacity is 8. In terms of distributed sensing, it can achieve a vibration response bandwidth ranging from 1 Hz to 2 kHz, a strain resolution of 0.50 , and a spatial resolution of 0.20 m under shot-noise-limited detection. The proposed ISAQN scheme enables simultaneous quantum communication and distributed sensing in a multipoint network, laying a foundation for future large-scale quantum networks and high-precision sensing networks.

Measurement of low-frequency electric field waveform by Rydberg atom-based sensor

The high polarizability of Rydberg atoms enables the multi-parameters measurement of electromagnetic fields. In this paper, we report on an atomic antenna based on Rydberg atoms in a room temperature vapor cell. The EIT is a destructive interference spectroscopy with a narrow linewidth and can be used to detect small electric fields through Autler-Townes splitting or Stark shifts. In our experiments, we employ cascade-type two-photon excitation electromagnetically induced transparency (EIT) spectroscopy to measure the shift of the Rydberg energy level. We introduce a low-frequency electric field (~kHz frequency) using a built-in electrode technique in the cesium cell. The interaction between the Rydberg atom and electric field induces the Stark shifts, where the amplitude of the electric field is converted into corresponding two-photon detuning by the EIT effect. Furthermore, the amplitude of the low-frequency electric field is converted into an intensity signal of EIT probe beam. Under weak field conditions, it is an approximate linear relationship between EIT transmission signal and input electric field amplitude, enabling measurement of waveform, amplitude, and frequency. We have demonstrated optical measurements of low-frequency electric field using Rydberg atoms. By increasing the power of probe beam and coupling beam, the EIT can increase the response bandwidth from ~MHz to hundreds of MHz. This provides a scalable approach for measuring high-frequency electric fields.

Embedding parametric resonance in a 2:1 wave energy converter to get a broader bandwidth

The effort to increase the converted power is a common challenge to players in the field of wave energy conversion, both academic and industrial. In the case devices are found to be prone to parametric resonance, it typically has a negative impact on power harvesting and may jeopardize the reliability of the device. This paper makes the case that parametric resonance is not a danger that should be avoided, but rather a chance to achieve a broader system response bandwidth and ultimately increase the amount of power available at the power take-off. Since a time-varying wetted surface causes the highly nonlinear phenomenon of parametric resonance, linear models are unable to fully capture this instability. As a result, nonlinear Froude–Krylov forces are herein implemented via a computationally effective method for prismatic floaters that is compatible with both exhaustive simulation methods and real-time computing, as the whole simulations runs up to 50 times faster than real-time. A novel pendulum-based device is intentionally defined to exhibit a 2:1 ratio between heave and pitch natural frequencies, causing parametric instability. Results demonstrate that linear models predict a single zone of meaningful potential power extraction around the pitch natural frequency, as expected; however, by using the designed attitude to develop parametric instability, a second additional region develops near the heave natural period. As a result, the free response bandwidth is in fact increased, making more energy available at the power take-off axis thanks to the nonlinear instability embedded in the wave energy converter.

Fog Computing for Control of Cyber-Physical Systems in Industry Using BCI.

Brain-computer interfaces use signals from the brain, such as EEG, to determine brain states, which in turn can be used to issue commands, for example, to control industrial machinery. While Cloud computing can aid in the creation and operation of industrial multi-user BCI systems, the vast amount of data generated from EEG signals can lead to slow response time and bandwidth problems. Fog computing reduces latency in high-demand computation networks. Hence, this paper introduces a fog computing solution for BCI processing. The solution consists in using fog nodes that incorporate machine learning algorithms to convert EEG signals into commands to control a cyber-physical system. The machine learning module uses a deep learning encoder to generate feature images from EEG signals that are subsequently classified into commands by a random forest. The classification scheme is compared using various classifiers, being the random forest the one that obtained the best performance. Additionally, a comparison was made between the fog computing approach and using only cloud computing through the use of a fog computing simulator. The results indicate that the fog computing method resulted in less latency compared to the solely cloud computing approach.

Array Study of VLF Thin-Film Magnetoelectric Antenna with a Microbridge Structure.

Recently, magnetoelectric (ME) antennas have become a hot topic in the field of antenna miniaturization in the very-low-frequency (VLF) band because their size can be reduced to one-ten-thousandth of the size of conventional electric antennas. However, they still suffer from narrow transmission/reception bandwidth and weak radiation intensity. To address these issues, VLF thin-film ME antennas with a microbridge structure are designed, and the method of array connection is used. Test results show that the detection limit of the ME antenna unit is 636 pT/√Hz at 23 kHz and the radiant magnetic field intensity at 0.12 m is 0.87 nT (input power of 10 mW). By series-connecting three ME antenna units with the same resonance frequency, the output response has been increased to 1.72 times and the EM wave radiation intensity is increased to 1.9 times compared to a single unit. By parallel-connecting two ME antenna units with different resonance frequencies, the output response bandwidth has been expanded to 1.56 times compared to a single unit, and the signal radiation bandwidth has been expanded to 1.47 times. This work provides a valuable reference for the future larger-scale arraying of ME antennas.

A Compact 16-Port Fractal Shaped Slot Antenna Array for 5G Smart Phone Communications

In this manuscript, a 16-port compact multi-antenna array for fifth generation (5G) communications is presented. The proposed antenna offers high data rate communication, by using MIMO (multiple-input-multiple-output) wireless technology. Efficient bandwidth enhancement techniques are used to achieve wider bandwidth response i.e., 3.4-3.8 GHz within sub-6GHz. This system is realized over low-cost FR-4 laminate having dimensions of 64mm × 131mm. The fractal shape slotted radiators and open-ended square ring (OESR) isolating structures achieves at least 25dB isolations among antenna pairs while maintaining wideband response. The optimum isolation, low-cost design profile, matched scattering parameters without compromising compactness and acceptable specific absorption rate (SAR) makes this system a suitable candidate for 5G smart phone communications.

Dual-band transmissive linear to circular polarization converter with angular-stable and orthogonal polarizations

Abstract A dual-band angular-stable transmissive linear to circular polarization converter based on metasurface is proposed and demonstrated in this work. The converter consists of three layers. The top and bottom layers are formed by an array of double split-ring layers. The unit cell of the central layer contains a square loop nesting a slant dipole. The split-rings create two resonances, enabling dual-band operation. The slant dipole and square loop are useful for improving the quality of circular polarization conversion. It is shown that the proposed polarization converter converts the incident linearly polarized wave into circularly polarized wave with opposite polarization modes over the frequency ranges of 8.77–10.58 and 17.59–19.88 GHz. The angular stability is up to 60° for 3 dB axial ratio. Moreover, the thickness of unit cell has a wavelength below 0.06 at the lower band. Compared with other designs in the literature, the structure bears merits of wideband response, high angular stability, and low-profile property within dual-band operational region. To validate the design, a sample prototype was designed, fabricated, and measured. The measured results are in good agreement with the simulated ones.

Matched impedance amplifier design for shear-force acoustic near-field microscopy

Efficient detection of the acoustic signal constitutes the most critical aspect in Shear-force Acoustic Near-field Microscopy, for reliably characterize the dynamic response of confined fluids under shear stress. The near-field acoustic emission from the fluid is monitored as the probe gradually approaches to, and subsequently retracts from, the substrate. Herein we report a 7dB improvement in signal-to-noise sensitivity in detecting the acoustic emission from the fluid trapped between a flat sample and the apex of a tapered probe (the latter attached to a quartz tuning fork of 32 kHz resonance frequency). The new design capitalizes on the inherent capacitance of the SANM acoustic sensor (comprising a pile of piezoelectric plates) and a proper matching inductor/capacitance combination to, altogether connected in a tank-circuit fashion, optimize the sensor’s response at 32 kHz. A detailed construction of the circuit amplifier, as well as detailed frequency response bandwidth and noise characterization, is included herein.