Asymmetric Resonance Research Articles

A balanced tri-band BPF with high selectivity based on ASSLR

Abstract In this paper, a balanced second-order tri-band bandpass filter (BPF) with high selectivity is proposed. Three differential-mode (DM) passbands are formed by applying one pair of asymmetric short stub-loaded resonators (ASSLRs) and uniform impedance resonators (UIRs) into the design. Meanwhile, the frequencies and bandwidths of the DM passbands can be quasi-independently controlled by the lengths of resonators and the gaps between them. In addition, broadband common-mode (CM) suppression is achieved intrinsically without affecting the DM parts based on the U-type balanced stepped-impedance microstrip-slotline transition (BSIMST) structures, thereby simplifying the design procedure significantly. In order to validate the practicability, a balanced tri-band BPF operating at 1.8, 3.5 and 4.45 GHz is fabricated and designed. A good agreement between the simulated and measured results is observed.

Design of a novel stub loaded asymmetric rectangular ring resonator based ultra-wide notched-band bandpass filter

This paper establishes a novel method to generate an ultra-wideband (UWB) bandpass filter (BPF) with four notches. Initially, this method employs a stub-loaded rectangular ring resonator (SLRRR) based compact structure to develop a UWB bandpass filter. Upgradation of the SLRRR structure into a stub-loaded asymmetric rectangular ring resonator (SLARRR) based structure in the next move facilitates the prospective filter with four notches at 4.34 GHz (S-band radar), 5.48 GHz (WLAN), 6 GHz (Wi-Fi 6E), and 9.3 GHz (X band radar) respectively possessing high rejection ability. This compact-sized (1.14λg × 0.29λg) proposed filter is characterized by a wide passband extending from 3.3 to 10.84 GHz with low insertion loss of <−0.69 dB, good selectivity of 0.8, and a 4.6 GHz wide upper stopband with −20 dB high rejection level. Structures are fabricated, measured, and compared with the obtained simulation outcomes. The resemblance between the compared results corroborates the applicability of such compact structure.

Carbon nanotube resonator enhancement of Majorana fermions induced slow light in a hybrid semiconductor/superconductor device

We theoretically investigate the Rabi-like splitting in the absorption spectrum of a single electron spin mediated by Majorana fermions in a hybrid semiconducting nanowire/superconductor system. The absorption spectra can display the symmetrical splitting phenomenon, and their related optical propagation such as fast light and slow light are investigated in different parametric regimes. When we consider implanting a spin into the carbon nanotube (CNT) resonator, the Rabi-like splitting in the absorption spectrum changes into asymmetric Fano resonance, which is accompanied by the rapid steep dispersion promising the slow- or fast-light effect, and even reaching tunable fast-to-slow light propagation (or vice versa) with controlling different parameter regimes. Moreover, we also investigate the role of the CNT resonator, which behaves as a phonon cavity enhancing the fast and slow light effect.

A novel coupled two-dimensional unsaturated asymmetric bistable stochastic resonance system for bearing fault detection

A novel coupled two-dimensional unsaturated asymmetric bistable stochastic resonance (NCTUABSR) method is proposed in this paper, which is formed by coupling a new asymmetric bistable controlled system with a monostable control system, and significantly solves the serious output saturation problem of traditional two-dimensional bistable system. Based on the SPD and MFPT, it is found that with the increase of coupling, the depth and distance of double potential wells in two-dimensional space will decrease, which makes the particles more prone to inter-well transition. Combined with SNR, the performance characteristics of NCTUABSR under the influence of different parameters are deeply analyzed. NCTUABSR is applied to different types of bearings for fault signal detection, and adaptive genetic algorithm is used to optimize the parameters. Compared with different coupling systems, it is found that the detection performance of NCTUABSR has the most advantages, indicating that the system has obvious feasibility in practical engineering applications.

Active Fano resonance switch using dual-layer graphene in an embedded dielectric metasurface.

We propose an active optical Fano switch (OFS) based on an embedded dielectric metasurface (EDM) including dual-layer graphene (DLG). An EDM is a dielectric grating overlapped by two cladding layers, and it excites a Fano resonance. DLG is positioned inside the upper cladding layer to maximize light-graphene interaction. Thus, with a small change of the chemical potential (µc) of graphene, a resonance wavelength is tuned to switch the OFS on and off. First, a red-parity asymmetric Fano resonance is realized, and a sharp asymmetric lineshape is achieved by controlling the structural parameters of the EDM and the interaction between the Fano resonance and additional weak Fabry-Perot interference for efficient switching. The distance of a peak-to-dip wavelength (Δλp-d) and the change of chemical potential (Δµc) for switching is analyzed by varying the duty cycle (DC) and grating thickness (tg) of the EDM. Furthermore, switching contrast as a figure of merit (FoM) is analyzed. With DC of 0.5 and tg of 70 nm, the OFS requires Δλp-d of 7.3 nm and Δµc of 0.25 eV. The FoM of 0.97 is achieved. By adjusting the two parameters, the switching condition is tuned. In the case of a blue parity, the effect of the two parameters exhibits a similar trend to that of the red parity. The FoM, however, is lower due to the reversed parity.

Performance of a resonant fiber-optic gyroscope based on a broadband source.

A resonant fiber-optic gyroscope (RFOG) based on a broadband source can avoid the fundamental drawback of coherence detection processing while possessing the greater sensitivity afforded by the finesse of the fiber-optic ring resonator. In this paper, the basic operation principle is presented and demonstrated in detail, and various noise sources, as well as the temperature effect encountered in this broadband source-driven RFOG, are studied and analyzed. Then a combined modulation technique is proposed to suppress the residual backscattering noise. To further reduce the effect of temperature transience, an asymmetric fiber ring resonator is designed. In the experiment, a bias stability of 0.01°/h is successfully demonstrated with a 100 m-long fiber ring resonator of 8 cm diameter in a laboratory environment without temperature control.

Angular distribution of γ rays from the p -wave resonance of Sn118

The neutron energy-dependent angular distribution of $\ensuremath{\gamma}$ rays from the $^{117}\mathrm{Sn}(n,\ensuremath{\gamma})$ reaction was measured with germanium detectors and a pulsed neutron beam. The angular distribution was clearly observed in $\ensuremath{\gamma}$-ray emissions with an energy of 9327 keV which corresponds to the transition from a neutron resonance of $^{117}\mathrm{Sn}+n$ to the ground state of $^{118}\mathrm{Sn}$. The angular distribution causes an angular-dependent asymmetric resonance shape. An asymmetry ${A}_{\mathrm{LH}}$ was defined as $({N}_{\mathrm{L}}\ensuremath{-}{N}_{\mathrm{H}})/({N}_{\mathrm{L}}+{N}_{\mathrm{H}})$, where ${N}_{\mathrm{L}}$ and ${N}_{\mathrm{H}}$ are integrated values for lower- and higher-energy regions of a neutron resonance, respectively. We found that the ${A}_{\mathrm{LH}}$ has the angular dependence of $(Acos{\ensuremath{\theta}}_{\ensuremath{\gamma}}+B)$, where ${\ensuremath{\theta}}_{\ensuremath{\gamma}}$ is the $\ensuremath{\gamma}$-ray emission angle with respect to the incident neutron momentum, with $A=0.394\ifmmode\pm\else\textpm\fi{}0.073$ and $B=0.118\ifmmode\pm\else\textpm\fi{}0.029$ in the 1.33 eV $p$-wave resonance.

Achieving polarization control by utilizing electromagnetically induced transparency based on metasurface

In this study, a design of transmissive linear-to-circular polarization conversion (LCPC) related to electromagnetically induced transparency (EIT) by arranging four sets of asymmetric resonators on a metasurface in a cross-shaped distribution is theoretically reported in the terahertz (THz) regime. It has numerically demonstrated that the bright modes and quasi-dark modes can also be mutually coupled when the x-polarized (TM) and y-polarized (TE) waves are incidents, resulting in a famous EIT phenomenon. Subsequently, when the direction of the electric fields of the electromagnetic (EM) waves are incident along the x-axis with an angle of 45°, the electric fields can be decomposed into the x- and y-directions. At this time, the corresponding amplitude and phase meet the conditions of the LCPC. Furthermore, for the TM and TE waves, the values of the maximum transmission coefficients respectively reach up to 0.910 at 1.384 THz and 0.890 at 1.277 THz. Correspondingly, two brand-new bright transparent windows are located in 1.276-1.454 THz for the TM waves and 1.206-1.373 THz for the TE waves. Concurrently, the band of the maximum 3 dB axial ratio is obtained from 1.308 THz to 1.343 THz with a relative bandwidth of 3%.

High power linearly polarized diode-side-pumped Nd:YAG laser based on an asymmetric flat–flat resonator with the variable working point

A high power linearly polarized diode-side-pumped Nd:YAG laser is demonstrated based on an asymmetric TEM00-mode flat–flat cavity with the birefringence compensation. Different from the traditional dynamically stable resonator, an asymmetric flat–flat resonator with the variable working point is designed theoretically and experimentally. Both of the Nd:YAG rods have a dimension of Φ5 mm × 130 mm and a doping concentration of 0.6 at.%. Under the pump power of 570 W, the maximum unpolarized output power of 111.7 W is achieved with an optical–optical efficiency of 19.6%. Using a Brewster plate, a linearly polarized output power of 80.1 W is obtained with the polarization extinction ratio of 18 dB, corresponding to the beam quality factors of ∼3.38 and ∼2.83 in the horizontal and vertical directions, respectively. To the best of our knowledge, this is the highest linearly polarized output power for a side-pumped two-rod Nd:YAG laser system with the asymmetric resonator.

A New Piecewise Nonlinear Asymmetry Bistable Stochastic Resonance Model for Weak Fault Extraction

In order to solve output saturation problems found in traditional stochastic resonance methods and to improve the diagnosis ability of weak faults, a new piecewise nonlinear asymmetric bistable stochastic resonance (PNABSR) method is proposed. This model uses a left and right potential function with an asymmetrical shape, which makes it easier to induce stochastic resonance phenomena. Based on the PNABSR model, the expression of the signal-to-noise ratio (SNR) is derived, and the changes in the SNR with different parameters in the PNABSR model are analyzed. Then, the parameters in the PNABSR model are optimized using the adaptive intelligent algorithm to enhance the diagnostic ability. The diagnosis properties of the weak fault are compared between the PNABSR model and the classical bistable stochastic resonance model (CBSR). The experimental results prove that the PNABSR model can effectively extract the weak fault characteristic frequency under a strong noise background, verifying the effectiveness of this method.

Refractive Index Sensor Based on a Metal-Insulator-Metal Bus Waveguide Coupled with a U-Shaped Ring Resonator.

In this study, a novel refractive index sensor structure was designed consisting of a metal-insulator-metal (MIM) waveguide with two rectangular baffles and a U-Shaped Ring Resonator (USRR). The finite element method was used to theoretically investigate the sensor’s transmission characteristics. The simulation results show that Fano resonance is a sharp asymmetric resonance generated by the interaction between the discrete narrow-band mode and the successive wide-band mode. Next, the formation of broadband and narrowband is further studied, and finally the key factors affecting the performance of the sensor are obtained. The best sensitivity of this refractive-index sensor is 2020 nm/RIU and the figure of merit (FOM) is 53.16. The presented sensor has the potential to be useful in nanophotonic sensing applications.

Dynamic control of Fano resonances in a coupled dual microring resonator system

We propose a coupled optical microresonator system that can be used as a new and flexible platform to form asymmetric Fano-like resonances and dynamically control their line shapes and frequencies. The coupled microresonator system was formed using two microring resonators coupled via a 3 × 3 coupler. The upper microring resonator is the add-drop type, whereas the lower one is the all-pass type, providing the (semi-) continuum and discrete states, respectively. We simulated the behavior of the coupled system using the finite-difference time-domain method and observed asymmetric Fano line shapes in the transmission spectra. We demonstrated that the line shapes and frequencies of Fano resonances can be controlled by dynamically varying the refractive index of a small region of the upper or lower microring resonators. We also introduced a small gap in the upper microring resonator to control the continuum state more efficiently. The proposed coupled microresonator concept is simple, easy to fabricate and sufficiently flexible to be engineered for different applications.

Refractive index sensor based on a ring with a disk-shaped cavity for temperature detection applications.

In this study, we proposed a novel refractive index sensor structure, comprising a metal-insulator-metal (MIM) waveguide and a circular ring containing a disk-shaped cavity (CRDC). The finite element method was used to theoretically analyze the sensor characteristics. The simulation results showed that the disk-shaped cavity is the key to the asymmetric Fano resonance, and the radius of the CRDC has a significant influence on the performance of the sensor. A maximum sensitivity and figure of merit (FOM) of 2240 nm/RIU and 62.5, respectively, were realized. Additionally, the refractive index sensor exhibits the potential of aiding in temperature detection owing to its simple structure and high sensitivity of 1.186 nm/ºC.

In-Filter Computing for Designing Ultralight Acoustic Pattern Recognizers

We present a novel in-filter computing framework that can be used for designing ultra-light acoustic classifiers for use in smart internet-of-things (IoTs). Unlike a conventional acoustic pattern recognizer, where the feature extraction and classification are designed independently, the proposed architecture integrates the convolution and nonlinear filtering operations directly into the kernels of a Support Vector Machine (SVM). The result of this integration is a template-based SVM whose memory and computational footprint (training and inference) is light enough to be implemented on an FPGA-based IoT platform. While the proposed in-filter computing framework is general enough, in this paper, we demonstrate this concept using a Cascade of Asymmetric Resonator with Inner Hair Cells (CAR-IHC) based acoustic feature extraction algorithm. The complete system has been optimized using time-multiplexing and parallel-pipeline techniques for a Xilinx Spartan 7 series Field Programmable Gate Array (FPGA). We show that the system can achieve robust classification performance on benchmark sound recognition tasks using only ~ 1.5k Look-Up Tables (LUTs) and ~ 2.8k Flip-Flops (FFs), a significant improvement over other approaches.

Electrically induced dynamic Fano-like resonance in a graphene-coated fiber grating

We created an all-fiber solution for fast, continuous, and controllable tuning of Fano-like resonance. By embedding a graphene-coated fiber Bragg grating into one arm of a Mach–Zehnder interferometer, the narrow Bragg resonance interacts with a broad interference spectrum, forming a sharp asymmetric Fano-like resonance line shape. With the application of an electrical voltage over the graphene layer, the generated Joule heating shifts the Bragg resonance and consequently tunes the asymmetric Fano-like resonance line shape to a symmetric dip or electromagnetically induced transparency-like peak. Further, by exploiting two modulated states with reversed Fano-like resonance line shapes, an optical switch can operate with an extinction ratio of 9 dB. The well-engineered Fano-like resonance in an all-fiber structure opens up new horizons for applications of fiber gratings in optical signal processing, slow-light lasing, and fiber sensing.

CROW-based Fano structures for all optical switching devices.

In this paper, an improved optical Fano switch based on coupled resonator optical waveguides (CROWs) is presented. The new topological design is employed to achieve steeper and highly asymmetric Fano resonances (FRs). Physically, in the proposed structures, due to the increase in the effective refractive index at the center of the CROW, a confined mode arises in the continuum background according to the variational theorem and leads to FR. The results show that in CROW-based Fano switches, the Fano spectrum is improved by tuning the number of nanocavities. The ratio between the slope ratio and linewidth shows an improvement of 55.25% from single to CROW5. As an important application of FR, an ultra-compact device with a CROW-based Fano structure is demonstrated. The results of the numerical finite difference time domain simulation agree well with the theoretical coupled mode theory.

Two asymmetric cylindrical dielectric resonator loaded dual port multiple‐input multiple‐output antenna for wide band application with circular polarization attributes

SummaryA novel multiple‐input multiple‐output double asymmetrical cylindrical dielectric resonator antenna (MIMO‐DCDRA) with modified stub line feed is discussed and proposed in this work. Two unequal CDRA are placed diagonally to each other and are electromagnetically coupled with feeding arrangement via two asymmetrical circular apertures. By performing the optimization of the dimensional parameters, a significant impedance bandwidth of 70.84% ranging from 2.87 to 5.76 GHz and axial ratio bandwidth (ARBW) of 34.89% is obtained. Antenna gain is about 5.0 dBi within the operating frequency. The proposed MIMO‐DCDRA exhibits a low mutual coupling of (|S21| &amp; |S12| &lt; −20 dB) with the incorporation of a neutralization line. There are various diversity parameters that are also discussed in terms of mutual coupling, envelop correlation coefficient (ECC &lt; 0.002), diversity gain (DG &gt; 9.995), and channel capacity loss (CCL &lt; 0.3 bits/s/Hz) over the entire impedance bandwidth.

Demonstration of multiple quantum interference and Fano resonance realization in far-field from plasmonic nanostructure in Er3+-doped tellurite glass

It is crucial to control the tuning and improve the emission of a quantum emitter at the nanoscale. We report multiple Fano resonances in metallic nanostructures on an Er3+-doped tellurite glass. Periodic nanoslits were fabricated with a focused gallium ion beam on a gold thin film deposited on the tellurite glass. Is proposed a coupling function with Fano line-shape form, and the asymmetric parameter q for each resonance wavelength in the 515 to 535 nm region was calculated. This asymmetric resonance effect is a consequence of the quantum interaction between the continuum state, generated in the nanostructure, and the Stark splits of the ^2H_{11/2} state.

Transflective spatial terahertz wave modulator

Spatial light modulators can digitally manipulate the amplitude, phase, and polarization of light. Their counterparts in the terahertz band are highly pursued to meet the requirements of numerous applications such as wireless communications and biomedical detection. Here, we propose a spatial terahertz wave modulator based on a liquid-crystal-integrated metadevice. The modulator consists of 8 × 8 pixels. The liquid crystal layer is sandwiched between an asymmetric split ring resonator array and pixelated interdigital electrodes. Fano resonance occurs for the transmitted wave, while the reflected wave is perfectly absorbed. By separately driving the liquid crystal with pixelated interdigital electrodes, both the Fano resonance and absorption peak can be continuously tuned due to the variation in the environmental refractive index. This work provides a transflective spatial terahertz wave modulator that can dynamically reconfigure a terahertz wavefront.

Silicon Nanodisk Huygens Metasurfaces for Portable and Low-Cost Refractive Index and Biomarker Sensing.

Biomarker detection and bulk refractive index sensing are important across multiple industries ranging from early medical diagnosis to chemical process quality control. The bulky size, high cost, and complex architecture of existing refractive index and biomarker sensing technologies limit their use to highly skilled environments like hospitals, large food processing plants, and research labs. Here, we demonstrate a compact and inexpensive refractive index sensor based on resonant dielectric photonic nanoantenna arrays or metasurfaces. These dielectric resonances support Mie dipole and asymmetric resonances that shift with changes in their external environment. A single-wavelength transmission measurement in a portable (<250 in.3), low-cost (<$4000) sensor shows sensitivity to 1.9 × 10–6 change in the fluid refractive index without the use of a spectrometer or other complex optics. Our sensor assembly allows for measurements using multiple metasurfaces with identical resonances or varying resonance types for enhanced diagnostics on the same chip. Furthermore, a 10 kDa culture filtrate peptide CFP-10, a marker for human tuberculosis, is detected with our sensor with 10 pM resolution. This system has the potential to enable facile, fast, and highly sensitive measurements with adequate limits of detection for personalized biomedical diagnoses.