Non-volatile dynamically switchable color display via chalcogenide stepwise cavity resonators

High-resolution multi-color printing relies upon pixelated optical nanostructures,which is crucial to promote color display by producing nonbleaching colors,yet requires simplicity in fabrication and dynamic switching.Antimony trisulfide(Sb_(2)S_(3))is a newly rising chalcogenide material that possesses prompt and significant transition of its optical characteristics in the visible region between amorphous and crystalline phases,which holds the key to color-varying devices.Herein,we proposed a dynamically switchable color printing method using Sb_(2)S_(3)-based stepwise pixelated Fabry-Pérot(FP)cavities with various cavity lengths.The device was fabricated by employing a direct laser patterning that is a less timeconsuming,more approachable,and low-cost technique.As switching the state of Sb_(2)S_(3) between amorphous and crystalline,the multi-color of stepwise pixelated FP cavities can be actively changed.The color variation is due to the profound change in the refractive index of Sb_(2)S_(3) over the visible spectrum during its phase transition.Moreover,we directly fabricated sub-50 nm nano-grating on ultrathin Sb_(2)S_(3) laminate via microsphere 800-nm femtosecond laser irradiation in far field.The minimum feature size can be further decreased down to~45 nm(λ/17)by varying the thickness of Sb_(2)S_(3) film.Ultrafast switchable Sb_(2)S_(3) photonic devices can take one step toward the next generation of inkless erasable papers or displays and enable information encryption,camouflaging surfaces,anticounterfeiting,etc.Importantly,our work explores the prospects of rapid and rewritable fabrication of periodic structures with nano-scale resolution and can serve as a guideline for further development of chalcogenide-based photonics components.

Asymmetrical Fabry-Perot cavity slot micro-ring resonator and its sensing characteristics

To achieve high quality factor and high-sensitivity refractive index sensor,a slot micro-ring resonator(MRR)based on asymmetric Fabry-Perot(FP)cavity was proposed.The structure consisted of a pair of elliptical holes to form an FP cavity and a microring resonator.The two different optical modes generated by the micro-ring resonator were destructively interfered to form a Fano line shape,which improved the system sensitivity while obtaining a higher quality factor and extinction ratio.The transmission principle of the structure was analyzed by the transfer matrix method.The transmission spectrum and mode field distribution of the proposed structure were simulated by the finite difference time domain(FDTD)method,and the key structural parameters affecting the Fano line shape in the device were optimized.The simulation results show that the quality factor of the device reached 22037.1,and the extinction ratio was 23.9 dB.By analyzing the refractive index sensing characteristics,the sensitivity of the structure was 354 nm·RIU−1,and the detection limit of the sensitivity was 2×10−4 RIU.Thus,the proposed compact asymmetric FP cavity slot micro-ring resonator has obvious advantages in sensing applications owing to its excellent performance.

Numerical Investigation on the Harbour Resonance Inside A Harbour with Lateral Cavities

Wave-induced harbour resonance is numerically investigated inside a harbour with lateral cavities.The theoretical solutions for the amplification parameter are compared with the simulated results under varying dimensionless wave numbers in order to verify the simulation model in a rectangular harbour at a constant depth.The results indicate that the numerical model can correctly calculate the natural frequency and the natural wave height.A range of calculations are performed for harbour resonance with one pair of lateral cavities,two pairs of lateral cavities and three pairs of lateral cavities,respectively.The simulated results indicate that the amplitude of the amplification parameter decreases both at the primary natural oscillation and the secondary natural oscillation,as the number of lateral cavities increases.The dimensionless wave number reduces as the number of lateral cavities increases both at the primary natural oscillation and the secondary natural oscillation as well.

Topological resonators based on hexagonal-star valley photonic crystals

In valley photonic crystals, topological edge states can be gained by breaking the spatial inversion symmetry without breaking time-reversal symmetry or creating pseudo-spin structures, making highly unidirectional light transmission easy to achieve. This paper presents a novel physical model of a hexagonal-star valley photonic crystal. Simulations based on the finite element method(FEM) are performed to investigate the propagation of TM polarized mode and its application to ring resonators. The results show that such a topologically triangular ring resonator exhibits an optimum quality factor Q of about 1.25×104, and Q has a maximum value for both frequency and the cavity length L. Our findings are expected to have significant implications for developing topological lasers and wavelength division multiplexers.

Design and high-power testing of offline conditioning cavity for CiADS RFQ high-power coupler

To validate the design rationality of the power coupler for the RFQ cavity and minimize cavity contamination,we designed a low-loss offline conditioning cavity and conducted high-power testing.This offline cavity features two coupling ports and two tuners,operating at a frequency of 162.5 MHz with a tuning range of 3.2 MHz.Adjusting the installation angle of the coupling ring and the insertion depth of the tuner helps minimize cavity losses.We performed electromagnetic structural and multiphysics simulations,revealing a minimal theoretical power loss of 4.3%.However,when the cavity frequency varied by110 kHz,theoretical power losses increased to10%,necessitating constant tuner adjustments during conditioning.Multiphysics simulations indicated that increased cavity temperature did not affect frequency variation.Upon completion of the offline high-power conditioning platform,we measured the transmission performance,revealing a power loss of 6.3%,exceeding the theoretical calculation.Conditioning utilized efficient automatic range scanning and standing wave resonant methods.To fully condition the power coupler,a 15°phase difference between two standing wave points in the condition-ing system was necessary.Notably,the maximum continuous wave power surpassed 20 kW,exceeding the expected target.

Effective transmittance of Fabry–Perot cavity under non-parallel beam incidence

The Fabry–Perot(FP) resonant cavity is widely used in laser and spectroscopic measurements due to its unique interference transfer function(ITF). In the ideal case of parallel incident light, the ITF of the FP resonant cavity can be expressed by the Airy function. However, in reality, it is difficult to achieve perfect parallelism with collimated beams. In this article, a theoretical model is established for non-parallel light incidence, which assumes that the non-parallel incident light is a cone-shaped beam, and the cone angle is used to quantify the non-parallelism of the beam. The transmittance function of the FP resonant cavity under non-parallel light incidence is derived. The accuracy of the model is experimentally verified. Based on this model, the effects of divergence angle, tilt angle and FP cavity parameters(reflectivity, cavity length)on the ITF are studied. The reasons for the decrease in peak value, broadening and asymmetry of the interference peak under non-parallel light incidence are explained. It is suggested that a fine balance between the interference peak and the collimation effect of the incident light should be considered in the design and application of FP resonant cavities, especially for tilted applications such as angle-scanned spectroscopy. The research results of this article have certain significance for the design and application of FP resonant cavities.

Single-Photon Transmission Characteristics in a Pair of Coupled-Resonator Waveguides Linked by a Nanocavity Containing a Quantum Emitter

Single-photon scattering in a pair of coupled-resonator arrays of waveguides linked by a nanocavity embedded with a two-level system is investigated theoretically.By using the discrete coordinates approach,we deduce the analytical expressions for the transmission and reflection amplitudes.The calculations reveal that the transport properties of the single photon can be controlled by adjusting the coupled strength between the nanocavity and the coupled-resonator array.Quantum switching and a 1/4 beam splitter for the band-edge photon based on this structure are also discussed.

Effect of Cavity Dimensions on TE_01δMode Resonance in Split-Post Dielectric Resonator Techniques

The effects of cavity dimensions on the resonance frequency and resonance strength of the TE01δmode in split postdielectric resonator (SPDR) technique are investigated by using full-wave simulations. The results of simulations provide guidance for adjusting the dimensional parameters of the set-up to ensure that a strong TE01δ resonance mode is excited. The scaled designs of SPDR fixtures for operation at frequencies that are most important for applications are presented. These designs employ two sets of dielectric resonators (DRs) that can be fabricated from the standard ceramic materials. In addition, it is demonstrated that the resonance frequency of the TE01δ mode in the fixture can be tuned by adjusting the gap of the split DR.

Tunneling effect in cavity-resonator-coupled arrays

The quantum tunneling effect （QTE） in a cavity-resonator-coupled （CRC） array was analytically and numerically investigated. The underlying mechanism was interpreted by treating electromagnetic waves as photons, and then was generalized to acoustic waves and matter waves. It is indicated that for the three kinds of waves, the QTE can be excited by cavity resonance in a CRC array, resulting in sub-wavelength transparency through the narrow splits between cavities. This opens up opportunities for designing new types of crystals based on CRC arrays, which may find potential applications such as quantum devices, micro-optic transmission, and acoustic manipulation.

Teleportation of two-atom entangled state in resonant cavity quantum electrodynamics

An alternative scheme is presented for teleportation of a two-atom entangled state in cavity quantum electrodynamics （QED）. It is based on the resonant atom-cavity field interaction. In the scheme, only one cavity is involved, and the number of the atoms needed to be detected is decreased compared with the previous scheme. Since the resonant atom-cavity field interaction greatly reduces the interaction time, the decoherence effect can be effectively suppressed during the teleportation process. The experimental feasibility of the scheme is discussed. The scheme can easily be generalized to the teleportation of N-atom Greeninger-Horne-Zeilinger （GHZ） entangled states. The number of atoms needed to be detected does not increase as the number of the atoms in the GHZ state increases.

Resonance suppression and electromagnetic shielding effectiveness improvement of an apertured rectangular cavity by using wall losses

The cavity-mode resonance effect could result in significant degradation of the shielding effectiveness （SE） of a shielding enclosure around its resonance frequencies. In this paper, the influence of coated wall loss on the suppression of the resonance effect is investigated. For this purpose, an equivalent circuit model is employed to analyze the SE of an apertured rectangular cavity coated with an inside layer of resistive material. The model is developed by extending Robinson＇s equivalent circuit model through incorporating the effect of the wall loss into both the propagation constant and the characteristic impedance of the waveguide. Calculation results show that the wall loss could lead to great improvement on the SE for frequencies near the resonance but almost no effect on the SE for frequencies far away from the resonance.

Novel method to measure unloaded quality factor of resonant cavities at room temperature

We demonstrated a novel method to measure the unloaded quality factor(Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was more reliable than traditional methods. The data required for the method were near the resonant frequency,not at the half-power points of the reflection coefficient curve or Smith chart. We applied the new method to measure a resonant cavity with an unloaded Q factor of^100,000, obtaining good agreement between the measured and theoretical results.

A new model for film bulk acoustic wave resonators

Based on cavity resonance and sandwich composite plate （3D） theoretical model for frequency dispersion characterization theory, this paper presents a universal three-dimensional and displacement profile shapes of the film bulk acoustic resonator （FBARs）. This model provides results of FBAR excited thickness-extensional and flexure modes, and the result of frequency dispersion is proposed in which the thicknesses and impedance of the electrodes and the piezoelectric material are taken into consideration; its further simplification shows good agreement with the modified Butterworth-Van-Dyke （MBVD） model. The displacement profile reflects the vibration stress distribution of electrode shapes and the lateral resonance effect, which depends on the axis ratio of the electrode shapes a/b. The results are consistent with the 3D finite element method modeling and laser interferometry measurement in general.

Nonperturbative solutions to cylindrical resonant cavities with dissipative medium and imperfectly conducting walls

Cylindrical waveguides without end surfaces can serve as two-dimensional resonant cavities. In such cavities the electromagnetic oscillations corresponding to an eigenfrequency can always be taken as TM or TE modes even when the walls have a finite conductivity and the medium is absorptive. This paper obtains analytic solutions to the field equations when the cylinder has a circular cross section. Some nonperturbative conclusions are drawn from the eigenvalue equation. Approximate analytic results for the resonant frequencies are obtained when the absorption of the medium is small and the walls are good conductors. Stability of the eigen modes is discussed. Similar results for the coaxial line are presented.

Optimization of Sound Absorption and Insulation Performances of a Dual-Cavity Resonant Micro-Perforated Plate

This study investigates a dual-cavity resonant composite sound-absorbing structure based on a micro-perforated plate.Using the COMSOL impedance tube model,the effects of various structural parameters on sound absorption and sound insulation performances are analyzed.Results show that the aperture of the micro-perforated plate has the greatest influence on the sound absorption coefficient;the smaller the aperture,the greater is this coefficient.The thickness of the resonance plate has the most significant influence on the sound insulation and resonance frequency;the greater the thickness,the wider the frequency domain in which sound insulation is obtained.In addition,the effect of filling the structural cavity with porous foam ceramics has been studied,and it has been found that the porosity and thickness of the porous material have a significant effect on the sound absorption coefficient and sound insulation,while the pore size exhibits a limited influence.

A research on high-temperature permittivity and loss tangent of low-loss dielectric by resonant-cavity technique

Resonant-cavity technique was introduced to measure the permittivity and loss tangent of low-loss dielectrics. The dielectric properties at 9-10 GHz are measured accurately at the temperature up to 800 ℃ by the resonant cavity technique. The only electrical parameters that need to be measured are quality factors （Q） and resonant length （L） of resonant cavity loaded and unloaded with dielectric sample. Moreover, the error caused by thermal expansion effect was resolved by error analysis and experimental calibration.

High-performance Refractive Index Sensor Based on Photonic Crystal Single Mode Resonant Micro-cavity

An effective refractive index sensor built with square lattice photonic crystal is proposed,which can be applicable to photonic integrated circuits.Two photonic crystal waveguides rather than conventional ridge waveguides are used as entrance/exit waveguides to the micro-cavity.Three layers of photonic lattice are set between the photonic crystal waveguides and the micro-cavity to achieve both a high transmission and a high sensitivity.The plane wave method is utilized to calculate the disperse curves and the finite difference time domain scheme is employed to simulate the light propagation.At the resonant wavelength of about 1500 nm,the resonant wavelength shifts up by 0.7 nm for each increment of Δn=0.001.A transmission of more than 0.75 is observed.Although the position disorder of the photonic crystal doesn't affect the sensitivity of the sensor, the transmission reduces rapidly as the disorder increases.

Enhanced surface plasmon interference lithography from cavity resonance in the grating slits

Surface plasmon interference lithography based on grating diffraction has been studied both theoretically and ex- perimentally in recent years. In this paper, we demonstrate that the cavity resonance in the grating slits can improve the subwavelength interference, not only the intensity but also the uniformity of the pattern. Both the typical lithography structure which merely consists of periodic metallic gratings and the modified structure equipped with a reflection layer are studied. The finite element method has been performed to study the interference pattern. Numerical simulations show that the property of the interference pattern is the optimum when cavity resonance happens. This enhancement can be applied to all the lithography structures which are based on the grating diffraction.

Preparation of W state in resonant bimodal cavity quantum electrodynamics

A scheme is proposed for generating entangled W states with four cavity modes. In this scheme, we send a V-type three-level atom through two identical two-mode cavities in succession. After the atom exits from the second cavity, the four cavity modes are prepared in the W state. On the other hand we can obtain three-atom W states by sending three V-type three-level atoms through a two-mode cavity in turn. The present scheme does not require conditional measurement, and it is easily generalized to preparing 2n-mode W states and n-atom W states.

Complete eigenmode analysis of a ladder-type multiple-gap resonant cavity

A theoretical model is developed for calculating the eigenmodes of the multi-gap resonant cavity. The structure of concern is a kind of ladder-type circuit, offering the advantages of easy fabrication, high characteristic impedance （R/Q）, and thermal capacity in the millimeter wave to THz regime. The eigenfunction expansion method is used to establish the field expressions for the gaps and the coupling region. Then, the match conditions at the interface are employed, which leads to a group of complicate boundary equations in the form of an infinite series. To facilitate the mathematical treatments and perform a highly efficient calculation, these boundary equations are transformed into the algebraic forms through the matrix representations. Finally, the concise dispersion equation is obtained. The roots of the dispersion equation include both the axial modes in the gaps, which include the fundamental and the high-order modes, and the cavity modes in the coupling region. Extensive numerical results are presented and the behaviors of the multi-gap resonant cavity are examined.