Resonator Losses Research Articles

Aerosol Jet Printed, Microwave Microstrip Ring Resonators for System-In-Package Applications

This article presents the design, simulation, and fabrication of printed microstrip transmission line (TL) and microwave ring resonators using aerosol-jet printing for system-in-package applications. The printed TLs are 8 mm long and their S-parameters are measured over a wide bandwidth ranging from 1 to 26 GHz. Their insertion loss ranges between 0.02 dB/mm at 1 GHz and 0.56 dB/mm at 26 GHz. Ring resonators were designed and printed to operate at center frequencies of 15.5, 17.5, 19.5, and 21.5 GHz by tuning the size of the ring. Variability studies are carried out to evaluate the ability of the printing process to fabricate reproducible devices. The coupling gap is optimized in order to minimize the insertion loss in the ring resonators without compromising $Q$ -factor. The simulations show good agreement with the experimental results. The ability to print both conductors as well as dielectrics for the fabrication of microwave resonators demonstrate the potential for in-package integration of RF resonators for low-cost sensor applications.

Energy Band Attraction Effect in Non-Hermitian Systems.

The energy band attraction (EBA) caused by the nonorthogonal eigenvectors is a unique phenomenon in the non-Hermitian (NH) system. However, restricted by the required tight-binding approximation and meticulously engineered complex potentials, such an effect has never been experimentally demonstrated before. Here by a suitable design of all-dielectric Mie resonators in a parallel-plate transmission line, we for the first time verify the photonic analog of the EBA effects both theoretically and experimentally. The evolution of the EBA effect in a two-level NH system from gapped bands to gapless bands to flat bands is observed by precisely tuning the loss of the Mie resonators. The transmission spectra can be theoretically connected to the eigenvalues and eigenvectors of the NH Hamiltonian. Furthermore we extend our methods to a graphenelike two-dimensional NH system. Our works show a metamaterial approach toward NH topological photonics and foster a deeper understanding of band theory in open systems.

Noise Performance of Single-Mode VCSELs: Dependence on Current Confinement and Optical Loss

We investigate the intensity and phase noise properties of GaAs-based 1060 nm oxide-confined single-mode vertical-cavity surface-emitting lasers (VCSELs) and their dependence on slope efficiency and current spreading, parameters that control the achievable output power. We find strong dependence of the linewidth on slope efficiency because it affects the optical resonator loss and therefore the spontaneous emission rate and the photon density. Likewise, we find strong dependence of the relative intensity noise on the slope efficiency since the optical resonator loss controls the photon lifetime, and therefore the damping of the relaxation oscillations. There is no noticeable dependence on transverse current confinement and current spreading. We measure linewidths as small as 6 MHz which we attribute to a small linewidth enhancement factor. This assumption is supported by calculations of the linewidth enhancement factor from optical resonator and optical gain simulations. The dependencies of noise on design parameters are general and therefore valid for single-mode VCSELs at other wavelengths and in other material systems.

Ringing Suppression of SiC MOSFET Using a Strongly Coupled External Resonator Through Analogy With Passive PT-Symmetry

Suppressing parasitic ringing, unwanted oscillation caused by switching, sufficiently and reliably, is of great importance in wide bandgap semiconductor devices. RC-circuits inserted in parallel with switching devices have been widely used to suppress such parasitic ringing in power electronics circuits due to simple configurations. However, short-circuit current would flow through power lines if capacitors are broken. In this article, we show that parasitic ringing can be damped with an external RLC resonator implemented in parallel to a bus bar. The configuration enables the strong magnetic coupling, which results in high ringing suppression effect. Moreover, the external resonator is designed through analogy with passive parity-time (PT) symmetry. In the range of unbroken phase, ringing energy is distributed effectively to the external resonator, and the damping rate is increased by increasing the loss of the external resonator. Our results represent a significant step toward practical applications of passive PT-symmetry.

Gain-induced scattering anomalies of diffractive metasurfaces

Abstract Photonic nanostructures with gain and loss have long been of interest in the context of diverse scattering anomalies and light-shaping phenomena. Here, we investigate the scattering coefficients of simple gain-doped diffractive metasurfaces, revealing pairs of scattering anomalies surrounded by phase vortices in frequency–momentum space. These result from an interplay between resonant gain, radiative loss, and interference effects in the vicinity of Rayleigh anomalies. We find similar vortices and singular points of giant amplification in angle-resolved reflectivity spectra of prism-coupled gain slabs. Our findings could be of interest for gain-induced wavefront shaping by all-dielectric metasurfaces, possibly employing gain coefficients as low as ∼50 cm−1.

Effect of geometric imperfections on anchor loss and characterisation of a gyroscope resonator with high quality factor

A critical functional part of a hemispherical resonator gyroscope (HRG) is the mechanical resonator, and a few million quality factor (Q-factor) is needed for the lowest resolution. This paper focuses on anchor loss of a HRG of a few millimeters in size. A detailed parametric study of dimensions and shell imperfections due to fabrication is carried out. A sensitivity study of the effect of shell mean radius, shell thickness, stem radius, stem height on the Qanchor is carried out. The effect of geometric imperfections such as shell offset, shell tilt, shell thickness variation, and unbalance is studied in detail. From the study, it is inferred that the anchor loss becomes very significant and approaches other loss mechanisms even with minor geometric imperfections in the hardware realisation. Based on the sensitivity study, the dimensional and geometric tolerances are arrived for precision fabrication. Precision resonator is fabricated as per the requirement of minimum anchor loss. The significance of other damping mechanisms such as air damping, excitation-induced damping, thermoelastic dynamic damping and surface dissipation is also discussed. Surface characterisation before and after surface treatment has been carried out using nanoindentation technique with regard to surface loss. Functional parameters of operating frequency and Q-factor are evaluated using laser Doppler vibrometry (LDV).

C,N-codoped MoSi2 ceramic with excellent heat resistance for microwaves absorption application.

Microwave absorption (MA) materials with high heat resistance have a wide range of applications in many fields. In this work, a C,N-codoped MoSi2 ceramic was prepared via a facile solid-phase reaction method and its MA properties was investigated. On the one hand, the results indicate that this ceramic possesses excellent heat resistance and the weight of the MoSi2 is almost constant when the temperature is lower than 800°C. On the other hand, this ceramic shows good MA performance when the filler loading ratio increases to 30 vol%, the value of reflection loss (RL) could reach to −17.70 dB at 7.44 GHz with the thickness of 2.0 mm and the effective electromagnetic absorption bandwidth (RL below −10 dB) could reach to 1.88 GHz (9.28–11.16 GHz) with the thickness of 1.5 mm. Multi-polarization resonance loss is considered as the predominant attention mechanism on the MA performance of this MoSi2 ceramic. This research provides a new idea for understanding resonance mechanism and greatly expands the application scope of MoSi2 ceramic in MA area.

Effects of nonlinear loss in high-Q Si ring resonators for narrow-linewidth III-V/Si heterogeneously integrated tunable lasers.

High-Q Si ring resonators play an important role in the development of widely tunable heterogeneously integrated lasers. However, while a high Q-factor (Q > 1 million) is important for ring resonators in a laser cavity, the parasitic high-power density in a Si resonator can deteriorate the laser performance at high power levels due to nonlinear loss. Here, we experimentally show that this detrimental effect can happen at moderate power levels (a few milliwatts) where typical heterogeneously integrated lasers work. We further compare different ring resonators, including extended Si ring resonators and Si3N4 ring resonators and provide practical approaches to minimize this effect. Our results provide explanations and guidelines for high-Q ring resonator designs in heterogeneously integrated tunable lasers, and they are also applicable for hybrid integrated butt-coupled lasers.

Optimized compact wideband reactive silencers with annular resonators

This paper presents a theoretical examination of wave propagation in a cylindrical duct loaded with an array of closely spaced flush-mounted annular resonators forming a simple reactive silencer. A semi-analytical mathematical model is proposed considering higher evanescent modes in the duct and plane-wave- and first transverse mode in annular resonators. Viscothermal losses in annular resonators are considered by employing the equivalent-fluid model. A heuristic optimization algorithm based on the proposed mathematical model is used to maximize the minimum transmission loss in a given frequency range. The numerical results show that multiple resonances of the individual resonators can be effectively utilized to design compact (thin) silencers with a wide frequency range and a relatively small number of resonators. The numerical results are validated by comparison with finite element simulations.

Lowest threshold lasing modes localized on marginally unstable periodic orbits in a semiconductor microcavity laser.

The lowest threshold lasing mode in a rounded D-shape microcavity is theoretically analyzed and experimentally demonstrated. To identify the lowest threshold lasing mode, we investigate threshold conditions of different periodic orbits by considering the linear gain condition due to the effective pumping region and total loss consisting of internal and scattering losses in ray dynamics. We compare the ray dynamical result with resonance mode analysis, including gain and loss. We find that the resonance modes localized on the pentagonal marginally unstable periodic orbit have the lowest threshold in our fabrication configuration. Our findings are verified by obtaining the path lengths and far-field patterns of lasing modes.

Asymmetric loss-induced perfect sound absorption in duct silencers

We investigate a duct silencer consisting of coupled resonators for perfect sound absorption. The device is composed of pairs of compact, ring-shaped Helmholtz resonators stacked along a duct. To study the effect of asymmetric intrinsic losses on the absorption performance, the resonators within each pair have the same dimensions (i.e., the identical resonance) but with different intrinsic losses. We find that the perfect absorption is realized by carefully choosing asymmetric intrinsic losses to the coupled resonators within each pair. The device with optimized losses exhibits exceptional point-like characteristics. This study provides not only a solution for practical duct systems but also allows thorough understanding of the role of asymmetric loss in degenerate resonators.

High permeability and bimodal resonance structure of flaky soft magnetic composite materials**Project supported by the National Natural Science Foundation of China (Grant Nos. 11564024, 51731001, and 11574122) and the Fundamental Research Funds for the Central Universities, China (Grant No. lzujbky-2019-kb06).

We establish a theoretical bimodal model for the complex permeability of flaky soft magnetic composite materials to explain the variability of their initial permeability. The new model is motivated by finding the two natural resonance peaks to be inconsistent with the combination of the domain wall resonance and the natural resonance. In the derivation of the model, two relationships are explored: the first one is the relationship between the number of magnetic domains and the permeability, and the second one is the relationship between the natural resonance and the domain wall resonance. This reveals that the ball milling causes the number of magnetic domains to increase and the maximum initial permeability to exist after 10 h of ball milling. An experiment is conducted to demonstrate the reliability of the proposed model. The experimental results are in good agreement with the theoretical calculations. This new model is of great significance for studying the mechanism and applications of the resonance loss for soft magnetic composite materials in high frequency fields.

Effect of Flow on Various Helmholtz Resonators

The acoustic performance of Helmholtz resonators with different configurations in the presence of mean flow is experimentally investigated. The transmission loss of Helmholtz resonators is measured using a flow-impedance tube setup to identify mean flow effects. First, Helmholtz resonators under two different flow conditions, grazing and direct flow, are considered at Ma=0.05 and 0.1. Then the impact of mean flow on the transmission loss of Helmholtz resonators with leakage holes is also demonstrated. For Helmholtz resonators with leakage holes, single peak of transmission loss is identified at Ma=0.0 and 0.1. However, two peaks appear at Ma=0.05 as the number of opening holes increases. The experimental results show that the effect of mean flow strongly depends on the configurations of Helmholtz resonators and the conditions of mean flow. Thus the variation of acoustic performance due to mean flow should be considered in the design of Helmholtz resonators.

Preparation and study of Ce2Fe17N3 microflakes with easy-plane anisotropy and high working frequencies

Soft magnetic composites (SMCs) are effective as magnetic powder cores in power transformers. Currently, SMCs used in transformers are mostly prepared from NiZn ferrites. One example of this type of material is NiZnCu ferrite, whose working frequency limit is 40 MHz. Above this frequency, its large magnetic loss angle tangent ( tanδm), approximately equal to 0.29 at 100 MHz, seriously impairs the property of transformers. Generally, the magnetic losses in the MHz frequency band result from eddy-current loss, domain wall resonance, and natural resonance, specifically the high natural resonance loss. A way to decrease it is by increasing the resonance frequency (fr). However, the increase in fr is very difficult for the uniaxially anisotropic NiZnCu ferrite due to the Snoek limit. We present a composite of oriented Ce2Fe17N3 microflakes and polyurethane in this letter. Although its true permeability is not as high as that of NiZnCu, the fr reaches 7.5 GHz. As a result, the tanδm at 100 MHz is decreased to 0.015. This indicates that our material has a higher working frequency than NiZnCu and should make fabrication of a 100 MHz transformer possible.

A 3-D-printed, temperature sensor based on mechanically-induced long period fibre gratings

ABSTRACTWe demonstrate the implementation of a temperature sensor based on mechanically induced long-period fibre gratings (MILPFGs) using a 3-D printing technology. Our sensor has an assembled structure with a periodically V-grooved plate, a flat cradle, and an assembly case, all of which are 3-D-printed with a thermoplastic of acrylonitrile butadiene styrene (ABS). Our sensor exhibits the linear change of both wavelength and loss of the resonance peak depending on environmental temperature, unlike the conventional LPFGs-based temperature sensors. The observed resonance loss change can be attributed to the micro-expansion of our 3-D-printed assembly structure, which decreases the screw-induced strain. The temperature sensitivities of our sensor are measured to be −97 pm/°C and 0.33 dB/°C for the wavelength and loss of the resonance peak, respectively.

Achieving excellent electromagnetic wave absorption of ZnFe2O4@CNT/polyvinylidene fluoride flexible composite membranes by adjusting processing conditions

The magnetic ZnFe2O4 nanoparticles were synthesized and combined with carbon nanotubes (CNTs) to form a unique tangled structure (ZnFe2O4@CNT), and then used as wave absorbing functional nanofillers of polyvinylidene fluoride (PVDF) matrix. The effects of ZnFe2O4@CNT functional nanofillers on the microstructure, crystallization behavior and electromagnetic wave absorption properties of PVDF were studied. The ZnFe2O4@CNT/PVDF composite membranes containing 7 wt% nanofillers presented an optimal reflection loss of −54.5 dB with a sample thickness of 2.4 mm when the processing temperature was 60 °C. If the processing temperature of 150 °C was adopted, the composite membranes with a thickness of only 2.0 mm surprisingly achieved an effective absorption of the whole X-band. The combination of interfacial polarization, polarization relaxation loss, dipole polarization, conductivity loss, and ferromagnetic resonance loss promoted the excellent microwave energy dissipation capacity of ZnFe2O4@CNT/PVDF system.

Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy

The field of magnon spintronics is experiencing an increasing interest in the development of solutions for spin-wave-based data transport and processing technologies that are complementary or alternative to modern CMOS architectures. Nanometer-thin yttrium iron garnet (YIG) films have been the gold standard for insulator-based spintronics to date, but a potential process technology that can deliver perfect, homogeneous large-diameter films is still lacking. We report that liquid phase epitaxy (LPE) enables the deposition of nanometer-thin YIG films with low ferromagnetic resonance losses and consistently high magnetic quality down to a thickness of 20 nm. The obtained epitaxial films are characterized by an ideal stoichiometry and perfect film lattices, which show neither significant compositional strain nor geometric mosaicity, but sharp interfaces. Their magneto-static and dynamic behavior is similar to that of single crystalline bulk YIG. We found, that the Gilbert damping coefficient alpha is independent of the film thickness and close to 1 x 10-4, and that together with an inhomogeneous peak-to-peak linewidth broadening of delta H0|| = 0.4 G, these values are among the lowest ever reported for YIG films with a thickness smaller than 40 nm. These results suggest, that nanometer-thin LPE films can be used to fabricate nano- and micro-scaled circuits with the required quality for magnonic devices. The LPE technique is easily scalable to YIG sample diameters of several inches.

Upconversion pumping of a 2.3 µm Tm3+:KY3F10 laser with a 1064 nm ytterbium fiber laser.

We report efficient lasing of the isotropic ${{\rm Tm}^{3 + }}\!:\!{{\rm KY}_3}{{\rm F}_{10}}$Tm3+:KY3F10 crystal near 2.3 µm via upconversion pumping with a 1064 nm ytterbium fiber laser as the pump source. When pumped at 1064 nm, an x-cavity ${{\rm Tm}^{3 + }}\!:\!{{\rm KY}_3}{{\rm F}_{10}}$Tm3+:KY3F10 laser operated at the free-running wavelength of 2344 nm. Lasing was obtained with output couplers having transmissions in the range of 1-3%, and as high as 124 mW of continuous-wave (cw) output power was generated with 604 mW of absorbed pump power by using the 3% output coupler. Broadly tunable cw lasing could be obtained in the 2268-2373 nm wavelength range. An analysis of the experimental power efficiency data shows that nearly all of the absorbed pump photons were converted to 2.3 µm laser output after accounting for the quantum defect of the laser transition and resonator losses. We expect that higher lasing efficiency should be possible by using longer crystals to increase the pump absorption.

Subwavelength dielectric resonators for nonlinear nanophotonics.

Subwavelength optical resonators made of high-index dielectric materials provide efficient ways to manipulate light at the nanoscale through mode interferences and enhancement of both electric and magnetic fields. Such Mie-resonant dielectric structures have low absorption, and their functionalities are limited predominantly by radiative losses. We implement a new physical mechanism for suppressing radiative losses of individual nanoscale resonators to engineer special modes with high quality factors: optical bound states in the continuum (BICs). We demonstrate that an individual subwavelength dielectric resonator hosting a BIC mode can boost nonlinear effects increasing second-harmonic generation efficiency. Our work suggests a route to use subwavelength high-index dielectric resonators for a strong enhancement of light-matter interactions with applications to nonlinear optics, nanoscale lasers, quantum photonics, and sensors.

Enhanced FSR Asymmetrical Triple Optical Ring Resonator

The paper proposes an Asymmetrical Triple Optical Ring Resonator (ATORR) and investigates its performances. Delay line signal processing scheme along with Mason’s Gain Formula is implemented to develop the transfer function of this configuration. Two different materials are used for this model, i.e., SOI (2.0167) and SIN (2.811), and their frequency responses are analyzed and compared to obtain different Free Spectral Range (FSR) outputs on MATLAB. Along with widening of FSR, crosstalks and resonance loss are also reduced. The extended FSR output is in THz range that has wide application in the field of photonics.