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Transient chaos is very common in periodically forced dynamical systems, but transient strange nonchaotic dynamics have not been studied by researchers. Therefore, it is meaningful to explore the dynamical phenomena of transient chaos and transient strange nonchaos. In this paper, we investigate a quasiperiodically forced cantilever beam system with impacts and discover abundant transient dynamic phenomena. Firstly, we determine the transient interval by the bifurcation diagram and the maximum Lyapunov exponent and investigate the correspondence between them. Secondly, we identify transient chaos and transient strange nonchaos and distinguish transient attractors and permanent attractors using the maximum Lyapunov exponent. Furthermore, we verify the strange property of attractors through the phase sensitivity and the power spectrum. [ABSTRACT FROM AUTHOR]

For the purpose of detecting waterborne bacteria, a high-phase-sensitivity SPR sensor with an Ag–TiO2–Franckeite–WS2 hybrid structure is designed using an improved seeker optimization algorithm (ISOA). By optimizing each layer of sensor construction simultaneously, the ISOA guarantees a minimum reflectance of less than 0.01 by Ag (20.36 nm)–TiO2 (6.08 nm)–Franckeite (monolayer)–WS2 (bilayer) after 30 iterations for E. coli. And the optimal phase sensitivity is 2.378 × 106 deg/RIU. Sensor performance and computing efficiency have been greatly enhanced using the ISOA in comparison to the traditional layer-by-layer technique and the SOA method. This will enable sensors to detect a wider range of bacteria with more efficacy. As a result, the ISOA-based design idea could provide SPR biosensors with new applications in environmental monitoring. [ABSTRACT FROM AUTHOR]

We have theoretically investigated the phase sensitivity of the hybrid interferometer with two coherent beams using the method of balance homodyne detection. The measurement device is a nonlinear–linear hybrid interferometer consisting of an optical parametric amplifier and a beam splitter. We prove that the phase sensitivity can beat the shot noise limit in the optimal conditions. Furthermore, we derive the quantum Cramér–Rao bound of the hybrid interferometer. The effects of transmission loss and detection loss on the measurement accuracy are discussed. The detection accuracy of this scheme is compared with that of the conventional SU (1,1) interferometer. Our results show that this scheme outperforms the conventional SU (1,1) interferometer scheme at high parametric strength. This scheme can be implemented with existing experimental techniques and will have important applications in quantum precision measurements. [ABSTRACT FROM AUTHOR]

We propose a theoretical scheme to improve the phase sensitivity by introducing the number-conserving generalized superposition of product into squeezed thermal state of the traditional SU(1,1) interferometer with intensity detection. We investigate the effect of different parameter and photon losses on phase sensitivity under the condition of the ideal and the realistic phase estimation process, respectively. Moreover, compared with the previous methods, our scheme can not only enhance the phase sensitivity, but also significantly suppress the photon losses with only first-order GSP operation. It means that our scheme needs less resources and less operations to obtain higher phase sensitivity. These above results indicate that our scheme is viable in the phase sensitivity improvement, which may have practical applications in quantum information processing.

We study the phase sensitivity of a Mach–Zehnder interferometer (MZI) with product detection (PD) scheme by using the superposition of Schrödinger’s cat-like state with the vacuum state (SCVS) and the coherent state as the inputs. We compare the results derived from PD with the parity detection scheme’s results. We found that PD performs better than parity detection and approaches the single parameter quantum Cramér-Rao bound in some cases. Therefore, we expect that SCVS may play as an alternative quantum resource with PD for the improvement in the phase sensitivity of an MZI having potential application in quantum metrology and quantum sensing.

A differential evolution particle swarm optimization (DEPSO) is presented for the design of a high-phase-sensitivity surface plasmon resonance (SPR) gas sensor. The gas sensor is based on a bilayer metal film with a hybrid structure of blue phosphorene (BlueP)/transition metal dichalcogenides (TMDCs) and MXene. Initially, a Ag-BlueP/TMDCs-Ag-MXene heterostructure is designed, and its performance is compared with that of the conventional layer-by-layer method and particle swarm optimization (PSO). The results indicate that optimizing the thickness of the layers in the gas sensor promotes phase sensitivity. Specifically, the phase sensitivity of the DEPSO is significantly higher than that of the PSO and the conventional method, while maintaining a lower reflectivity. The maximum phase sensitivity achieved is 1.866 × 106 deg/RIU with three layers of BlueP/WS2 and a monolayer of MXene. The distribution of the electric field is also illustrated, demonstrating that the optimized configuration allows for better detection of various gases. Due to its highly sensitive characteristics, the proposed design method based on the DEPSO can be applied to SPR gas sensors for environmental monitoring. [ABSTRACT FROM AUTHOR]

Attention can be selectively tuned to particular features at different spatial locations or objects. The deployment of attention can be guided by properties, such as color, orientation, and so forth, as guiding features. What might be such guiding features for visual stimuli under dynamic rhythmic conditions? We asked specifically what might be the parameters that attract attention when perceiving a visual rhythm. We used a visual search paradigm, in which a dynamic search display consisted of vertically "bouncing balls" with regular rhythms. The search target was defined by a unique visual rhythm (i.e., with either a shorter or longer period) among rhythmic distractors sharing an identical period. We modulated amplitudes and phases of the distractor balls systematically. The results showed a crucial factor of the phase, not the amplitude. If the phase is violated, the target suddenly "pops out" as an "oddball," showing an efficient parallel search. The findings indicate in general the essential role of the phase in conjunction with amplitude and period for visual rhythm perception. Furthermore, a higher saliency of moving objects with a higher frequency component has also been disclosed. [ABSTRACT FROM AUTHOR]

For the purpose of detecting waterborne bacteria, a high-phase-sensitivity SPR sensor with an Ag–TiO2–Franckeite–WS2 hybrid structure is designed using an improved seeker optimization algorithm (ISOA). By optimizing each layer of sensor construction simultaneously, the ISOA guarantees a minimum reflectance of less than 0.01 by Ag (20.36 nm)–TiO2 (6.08 nm)–Franckeite (monolayer)–WS2 (bilayer) after 30 iterations for E. coli. And the optimal phase sensitivity is 2.378 × 106 deg/RIU. Sensor performance and computing efficiency have been greatly enhanced using the ISOA in comparison to the traditional layer-by-layer technique and the SOA method. This will enable sensors to detect a wider range of bacteria with more efficacy. As a result, the ISOA-based design idea could provide SPR biosensors with new applications in environmental monitoring.

In this paper, we study strange nonchaotic attractors (SNAs) and multistable dynamics in a class of nonlinear economic systems. For quasiperiodically forced case, the generation and evolution mechanisms of SNAs are discussed. The fractal, Heagy–Hammel, torus doubling, and intermittency routes to SNAs are identified. The Lyapunov exponent, phase-sensitive function and power spectrum are used to characterize the dynamical and geometrical properties of SNAs. Moreover, when multistable phenomenon occur in the system, the boundaries of the basin of attraction may become intertwined, which leads to the economic unpredictability in the long run. [ABSTRACT FROM AUTHOR]

We study the improvement in the phase sensitivity of a Mach–Zehnder interferometer (MZI) using the superposition of 'Schrödinger's cat-like state with the vacuum state (SCVS)' and the vacuum state as inputs. With this setup, we examine the effect on the phase sensitivity of the interferometer using a parity detection scheme. We find better phase sensitivity under some conditions for this setup having potential application in quantum sensing. [ABSTRACT FROM AUTHOR]

We have conducted a study on a very-low-frequency acoustic-velocity sensor which is based on a cantilever of distributed-feedback (DFB) fiber laser immersed in castor oil. A mathematical model of the frequency dependent response of the proposed sensor to the acoustic pressure signal influenced by the fluid viscosity is established. We have fabricated the proposed sensor and conducted experimental measurements in the standing wave tube. The results show that the sensor has an average phase sensitivity of −179.5 dB (0 dB = 1 rad/μPa) with ±1.45 dB fluctuation over the frequency range of 20–38 Hz. It has good cosine directivity with a directivity index of 32.5 dB and axial maximum asymmetry of 0.4 dB. The sensor presents promising applications for detecting very-low-frequency underwater acoustic signals. [ABSTRACT FROM AUTHOR]

We attempt to demonstrate optical phase switches in a typical light storage experiment. We computed propagation dynamics of light pulses in sodium-23, rubidium-87, and potassium-39 vapors. These vapors have the same tensorial sets of the density matrix with a nuclear spin I = 3/2. The energy scheme is known as the double-Λ system. We considered an excitation mechanism in which one of two Λ systems was excited by two-color pulses, probe, and drive, following the standard electromagnetically induced transparency configuration. The probe channel contains delayed two pulses after the first probe pulse. Gain is generated through the drive channel and is exposed during propagation. We further investigated the spatiotemporal phase variations in the pulses and found discrete phase distribution for different vapors. The spatiotemporal evolution of the irreducible tensorial sets defines structural differential equations. Additionally, it is particularly suitable for parallel processing. We hope our study finds an application in comparison to alkali vapor magnetometry. [ABSTRACT FROM AUTHOR]

This work discusses the single-intensity and difference-intensity detection schemes for lossy Mach–Zehnder Interferometer (MZI) and gives the corresponding optimal conditions to achieve the best phase measurements. The interferometer is fed by a coherent state in one port and a vacuum state in the other. When the core parameters (reflectivities, phase difference) are optimal, the phase sensitivity of these two detection schemes can reach a generalized precision bound: the standard interferometric limit (SIL). In the experiment, we design an MZI with adjustable beam splitters to verify the phase sensitivity optimization compared to the conventional MZI with 50:50 beam splitters. The sensitivity improvements at loss rates from 0.4 to 0.998 are demonstrated based on difference-intensity detection, matching the theoretical results well. With a loss up to 0.998 in one arm, we achieve a sensitivity improvement of 2.5 dB by adjusting reflectivity, which equates to a 5.5 dB sensitivity improvement in single-intensity detection. Such optimal phase measurement methods provide practical solutions for the correct use of resources in lossy interferometers.

The topology of feedback optical parametric amplifier (FOPA) renders a number of significant advantages over the topology of traditional optical parametric amplifier (TOPA) such as a higher degree of quantum correlation, all-phase entanglement enhancement, and the robustness of the losses. Here, we propose a feedback-assisted interferometer based on the topology of FOPA for quantum metrology. We theoretically study the phase sensitivity with the method of homodyne detection and product detection. By manipulating the feedback strength of the FOPA, the phase sensitivity can be further enhanced, and approach the quantum Cramér-Rao bound. Furthermore, we demonstrate that our proposal is superior to the SU(1,1) interferometer based on the topology of TOPA.

An embodiment of a fiber-optic temperature sensor based on a Fabry-Perot interferometer and a scheme for interrogating an experimental sample of the sensor are proposed. The proposed solution makes it possible not to use expensive spectral measuring devices (spectrum analyzer, interrogator). The region of free dispersion and the phase sensitivity of the developed Fabry-Perot interferometer were determined in the temperature range from 20 °C to 590 °C. The accuracy of measuring the ambient temperature is calculated. The long-term stability of the measuring setup at room temperature has been evaluated. The phase shift of the Fabry-Perot interferometer with temperature change was registered. The design of the Fabry-Perot interferometer is implemented using reflective thin-film multilayer structures obtained by stage-bystage electron-beam deposition in vacuum on polished end cleavages of an optical fiber. The interferometer interrogation method is based on the use of a vertical-cavity surface-emitting laser (VCSEL) operating in a pulsed mode. The principle of registering the phase shift of the interferometer with a change in temperature is based on the use of auxiliary modulation of laser radiation along the wavelength due to modulation (periodic change) of the duration of optical pulses. Auxiliary modulation makes it possible to obtain additional harmonic components in the interferometer signal, which are further used in homodyne demodulation to restore the interferometer phase shift signal proportional to the change in the optical path difference between the interferometer mirrors. The design of the high-temperature sensor is based on a Fabry-Perot interferometer the reflecting mirrors of which are five alternating layers of thin films of TiO2 and Al2O3. Based on the results of the temperature experiment, it was concluded that an increase in the ambient temperature leads to a decrease in the free dispersion region of the Fabry-Perot interferometer. The conclusion made is consistent with the theoretical data. According to the results of the experiment, it is shown that the phase sensitivity of the interferometer to temperature changes is 0.94 rad/K. The accuracy of temperature measurements at the 3σ level was 0.017 K. The results of the study may be of great importance in creating systems for monitoring temperatures above 300 °C. The use of such an interferometer makes it possible to carry out high-precision relative temperature measurements.

Identifying the most plausible cause of the fringe pattern changes in the double-slit of psychophysical domain (Radin et al., 2012, 2013) not only is instrumental to the understanding of the nature of psychophysical effects that may manifest but also will shed light on the effecting mechanism of such anomalous faculty should it be quantifiable. We implement computer simulations of double-slit fringe patterns based on the Huygens-Fresnel principle using the primary experimental geometrical parameters of Radin et al. (2013) to assess how an asymmetry of the double-slit configuration could affect the fringe visibility. The main result is that the normalized interference fringe corresponding to an asymmetry of the electrical field magnitude of 3/1 or 1/3:1 as was modeled by Radin et al. (2013) is grossly indifferent from that caused by an asymmetry of the spectral bandwidth of 0.00205 nm between the two slits at 632.8 nm center wavelength. A spectral broadening of 0.00205 nm of the light for the experimental setting utilized by Radin et al. (2013) could correspond to a power change of no more than 10 picowatts. Further studies are warranted to test this hypothesis towards understanding the nature of psychophysical faculty as was conjectured with Radin's double-slit experiments. [ABSTRACT FROM AUTHOR]

An optical refractive index sensor with a metal-multilayer dielectric film structure based on Fano resonance (FR) is proposed to solve the low sensitivity of traditional surface plasmon resonance (SPR) sensors. The sensor’s performance can be optimized, and a plasmon-induced reflection (PIR) of incident light can also be achieved by adjusting the thickness of each layer. Through an innovative experimental design, the practical measurement phase sensitivity of the sensor based on FR is achieved for the first time, which provides a reference for subsequent theoretical research and experimental preparation. The wavelength sensitivity and the phase sensitivity can reach 345 nm/RIU and $4.00\times 10^{{5}\circ }$ /RIU, which experimentally proves that phase interrogation has higher sensitivity than traditional wavelength interrogation. The sensor can be a promising candidate for exploiting novel plasmonic sensors with ultrahigh sensitivity and resolution for biosensing applications. [ABSTRACT FROM AUTHOR]

A differential evolution particle swarm optimization (DEPSO) is presented for the design of a high-phase-sensitivity surface plasmon resonance (SPR) gas sensor. The gas sensor is based on a bilayer metal film with a hybrid structure of blue phosphorene (BlueP)/transition metal dichalcogenides (TMDCs) and MXene. Initially, a Ag-BlueP/TMDCs-Ag-MXene heterostructure is designed, and its performance is compared with that of the conventional layer-by-layer method and particle swarm optimization (PSO). The results indicate that optimizing the thickness of the layers in the gas sensor promotes phase sensitivity. Specifically, the phase sensitivity of the DEPSO is significantly higher than that of the PSO and the conventional method, while maintaining a lower reflectivity. The maximum phase sensitivity achieved is 1.866 × 106 deg/RIU with three layers of BlueP/WS2 and a monolayer of MXene. The distribution of the electric field is also illustrated, demonstrating that the optimized configuration allows for better detection of various gases. Due to its highly sensitive characteristics, the proposed design method based on the DEPSO can be applied to SPR gas sensors for environmental monitoring.

The phase image of tapping‐mode atomic force microscopy (TM‐AFM) contains energy dissipation, which is related to the sample information on the physical properties such as the sample Young's modulus, adhesion, surface morphology and subsurface morphology. When TM‐AFM is used for sample measurement, the frequency near the first resonance peak of probe is usually selected to drive the probe vibration. When the probe vibration is driven by the frequency, the probe has a high amplitude sensitivity, but the phase sensitivity is relatively low. In this paper, the frequency at the probe phase resonance peak was selected for driving the probe vibration to measure the sample, which improved the image resolution. Phase imaging was performed on three uniform photoresist samples with different thicknesses and the same structure. When the scanning parameters were fixed and the probe setpoint value was changed alone, it was found that with the decrease of setpoint value the horizontal resolution of the phase subsurface image was decreased, and the depth sensitivity was increased first and then decreased. The result shows that TM‐AFM working at the phase resonance peak can better realise the subsurface imaging of samples at different depths. Phase subsurface imaging at the resonance can be used to quantitatively obtain subsurface phase images of different depths. [ABSTRACT FROM AUTHOR]

The phase sensitivity of the condenser type acoustic transducers at low frequencies is crucial for locating large-scale natural and manmade activities, but is now commonly calibrated based on comparison methods. Although the primary method, which traces its sensitivity back to the international standard unit is few studied. Recently, the explicit sensitivity models of the condenser type acoustic transducers based on the laser-pistonphone technique are built, and can be used to study the phase responses of acoustic transducers at infrasonic frequencies. So that, in this paper, the phase sensitivities of acoustic transducers when its rear vent connected to the calibrating sound field or outside atmosphere are studied in detail. Secondly, time domain analysis of generated sound pressures by displacement excitation are derived to reveal the mechanism of phase variation. Calculations show two distinct sensitivities with 90° phase lead and −10° phase lag limits for vent in field and vent out field calibrations, which are dominated by the pressure leakage and heat conduction effects at infrasonic frequencies. [ABSTRACT FROM AUTHOR]

The basins of attraction of periodic orbits or focus equilibria of a given vector field are foliated by forward-time isochrons, defined as all initial conditions that synchronize under the flow with a given phase. Similarly, backward-time isochrons of repelling periodic orbits or focus equilibria foliate their respective basins of repulsion. We present a case study of a planar system that features a sequence of bifurcations, including a saddle-node bifurcation of periodic orbits, a homoclinic bifurcation and Hopf bifurcations, that change the nature and existence of periodic orbits. We explain how the basins and isochron foliations change throughout the sequence of bifurcations. In particular, we identify structurally stable tangencies between the foliations by forward-time and backward-time isochrons, which are curves in the plane, in regions of phase space where they exist simultaneously. Such tangencies are generically quadratic and associated with sharp turns of isochrons and phase sensitivity of the system. In contrast to the earlier reported cubic isochron foliation tangency (CIFT) mechanism, which generates a pair of tangency orbits, we find isochron foliation tangencies that occur along single specific orbits in the respective basin of attraction or repulsion. Moreover, the foliation tangencies we report arise from actual bifurcations of the system, while a CIFT is not associated with a topological change of the underlying phase portrait. The properties and interactions of isochron foliations are determined and illustrated by computing a representative number of forward-time and backward-time isochrons as arclength-parametrized curves with a boundary value problem set-up. Our algorithm for computing isochrons has been further refined and implemented in the Matlab package CoCo; it is made available as Matlab code in the supplementary material of this paper, together with a guide that walks the user through the computation of two specific isochron foliations. [ABSTRACT FROM AUTHOR]

Low frequency primary calibrations of condenser microphones are the basis of accurate measurement of low frequency sound and infrasound. Prior arts on the primary phase calibrations differ greatly, simultaneous primary amplitude and phase calibrations are rarely seen. Recently, two infrasonic sensitivity models of condenser microphones based on the pistonphone technique, for the vent immersed in sound field and outside are derived. The relevant models can explicitly characterize the influence of pistonphone, microphone and environment on the voltage output and sensitivity of the microphone. On this basis, simultaneous primary amplitude and phase calibration tests are evaluable. Based on adequate performance tests of the designed laser pistonphone, this paper carries out in-depth primary microphone calibrations. The calibrated infrasonic amplitude and phase sensitivities are in good agreement with theoretical results, thus proves their values to reveal and quantify the influence of various factors on the calibration results based on the pistonphone technique. [ABSTRACT FROM AUTHOR]

We have conducted a study on a very-low-frequency acoustic-velocity sensor which is based on a cantilever of distributed-feedback (DFB) fiber laser immersed in castor oil. A mathematical model of the frequency dependent response of the proposed sensor to the acoustic pressure signal influenced by the fluid viscosity is established. We have fabricated the proposed sensor and conducted experimental measurements in the standing wave tube. The results show that the sensor has an average phase sensitivity of −179.5 dB (0 dB = 1 rad/μPa) with ±1.45 dB fluctuation over the frequency range of 20–38 Hz. It has good cosine directivity with a directivity index of 32.5 dB and axial maximum asymmetry of 0.4 dB. The sensor presents promising applications for detecting very-low-frequency underwater acoustic signals.

Multimode integrated interferometers have great potential for both spectral engineering and metrological applications. However, the material dispersion of integrated platforms constitutes an obstacle that limits the performance and precision of such interferometers. At the same time, two-colour nonlinear interferometers present an important tool for metrological applications, when measurements in a certain frequency range are difficult. In this manuscript, we theoretically developed and investigated an integrated multimode two-colour SU(1,1) interferometer operating in a supersensitive mode. By ensuring the proper design of the integrated platform, we suppressed the dispersion, thereby significantly increasing the visibility of the interference pattern. The use of a continuous wave pump laser provided the symmetry between the spectral shapes of the signal and idler photons concerning half the pump frequency, despite different photon colours. We demonstrate that such an interferometer overcomes the classical phase sensitivity limit for wide parametric gain ranges, when up to 3 × 10 4 photons are generated. [ABSTRACT FROM AUTHOR]

We attempt to demonstrate optical phase switches in a typical light storage experiment. We computed propagation dynamics of light pulses in sodium-23, rubidium-87, and potassium-39 vapors. These vapors have the same tensorial sets of the density matrix with a nuclear spin I = 3/2. The energy scheme is known as the double-Λ system. We considered an excitation mechanism in which one of two Λ systems was excited by two-color pulses, probe, and drive, following the standard electromagnetically induced transparency configuration. The probe channel contains delayed two pulses after the first probe pulse. Gain is generated through the drive channel and is exposed during propagation. We further investigated the spatiotemporal phase variations in the pulses and found discrete phase distribution for different vapors. The spatiotemporal evolution of the irreducible tensorial sets defines structural differential equations. Additionally, it is particularly suitable for parallel processing. We hope our study finds an application in comparison to alkali vapor magnetometry.

In this study, we propose an improved theoretical model for the phase estimation scheme with inverse operations and compare it with the conventional phase estimation model in terms of the Fisher information and error propagation equation. In addition, we analyse the phase sensitivity of Mach-Zehnder Interferometer (MZI) and SU(1,1) interferometer (SU(1,1)I) with the coherent or squeezed states as input for intensity detection. We also discuss the phase sensitivity of MZI and SU(1,1)I with inverse displaced and inverse squeezed operations for intensity detection, and extensively compare them with and without the inverse operation scheme. Accordingly, we conclude that the phase sensitivity of interferometers can be significantly enhanced by embedding additional inverse operations. [ABSTRACT FROM AUTHOR]

We theoretically analyze the phase sensitivity of an SU (1 , 1) interferometer with various input states by product detection in this paper. This interferometer consists of two parametric amplifiers that play the role of beam splitters in a traditional Mach–Zehnder interferometer. The product of the amplitude quadrature of one output mode and the momentum quadrature of the other output mode is measured via balanced homodyne detection. We show that product detection has the same phase sensitivity as parity detection for most cases, and it is even better in the case with two coherent states at the input ports. The phase sensitivity is also compared with the Heisenberg limit and the quantum Cramér–Rao bound of the SU (1 , 1) interferometer. This detection scheme can be easily implemented with current homodyne technology, which makes it highly feasible. It can be widely applied in the field of quantum metrology. [ABSTRACT FROM AUTHOR]

The design, development, fabrication, and testing of a wideband reflectarray antenna with a novel concentric ring element operating over Ku/K band frequencies is presented in this paper. The element characterization is performed using the infinite array approach and is inferred that the proposed unit cell offers a higher phase variation of 643° by changing the size of the concentric rings. The proposed reflectarray antenna has a circular geometry and is constructed using 437 elements with an element separation of 0.43λ0. The proposed reflectarray offers a 3 dB gain bandwidth of 35% (15–21 GHz). The aperture efficiency is estimated to be 58.78% at 16.5 GHz. The prototype reflectarray is fabricated and tested to validate the simulation results. The measured peak gain of the reflectarray is 28.4 dBi with a side lobe level of −17.6 dB. The measured cross‐polarization level is less than −32 dB. Furthermore, it is inferred that the proposed unit cell has a reduced maximum phase sensitivity of 246°/mm with a gain selectivity of 6 dB at the lowest operating frequency. The proposed broadband reflectarray with enhanced performance characteristics is suitable for application in satellite communication and aeronautical radio navigation. [ABSTRACT FROM AUTHOR]

We propose a theoretical scheme to improve the phase sensitivity by introducing the number-conserving generalized superposition of product into squeezed thermal state of the traditional SU(1,1) interferometer with intensity detection. We investigate the effect of different parameter and photon losses on phase sensitivity under the condition of the ideal and the realistic phase estimation process, respectively. Moreover, compared with the previous methods, our scheme can not only enhance the phase sensitivity, but also significantly suppress the photon losses with only first-order GSP operation. It means that our scheme needs less resources and less operations to obtain higher phase sensitivity. These above results indicate that our scheme is viable in the phase sensitivity improvement, which may have practical applications in quantum information processing. • In the actual production process of the squeezed state light field, STS instead of the pure SVS may be generated due to some unavoidable losses and extra noise. • A novel non-Gaussian operation, the number-conserving generalized superposition of products (GSP) operation is applied on squeezed thermal state (STS) to further enhance the sensitivity of the phase estimation. • In addition, we shall compare the effects of different non-Gaussian operations on phase sensitivity, including PSA, PAS, as well as general generalized superposition. [ABSTRACT FROM AUTHOR]

Multimode integrated interferometers have great potential for both spectral engineering and metrological applications. However, the material dispersion of integrated platforms constitutes an obstacle that limits the performance and precision of such interferometers. At the same time, two-colour nonlinear interferometers present an important tool for metrological applications, when measurements in a certain frequency range are difficult. In this manuscript, we theoretically developed and investigated an integrated multimode two-colour SU(1,1) interferometer operating in a supersensitive mode. By ensuring the proper design of the integrated platform, we suppressed the dispersion, thereby significantly increasing the visibility of the interference pattern. The use of a continuous wave pump laser provided the symmetry between the spectral shapes of the signal and idler photons concerning half the pump frequency, despite different photon colours. We demonstrate that such an interferometer overcomes the classical phase sensitivity limit for wide parametric gain ranges, when up to 3×104 photons are generated.

This article presents a novel, compact reflectarray antenna operating at 5 GHz. The array consists of two types of phasing element - square ring and complementary square ring. The complementary square ring is used for the phase values that are not covered by the single ring element. The grid size of the array is 0.28λ × 0.28λ at operating frequency 5 GHz that is much smaller than the conventional periodicity 0.5λ × 0.5λ. The aim of unit cell design is to have a slower slope of the reflection phase graph without sacrificing the phase range of 360° where in general there is a trade-off between these two goals. The maximum slope in reflection phase graph is obtained here is 34°/mm. The proposed array is fabricated on a low loss PTFE substrate of thickness 3.175 mm (0.053λ at 5 GHz) and illuminated by a horn antenna. Radiation pattern results show a very precised far-field beam with 3-dB beamwidth of 7° and 7.3° for two principle planes respectively. The gain of the antenna is 26 dBi at 5 GHz.

Magnetoelastic sensors for the detection of low-frequency and low-amplitude magnetic fields are in the focus of research for more than 30 years. In order to minimize the limit of detection (LOD) of such sensor systems, it is of high importance to understand and to be able to quantify the relevant noise sources. In this contribution, cantilever-type electromechanical and magnetoelastic resonators, respectively, are comprehensively investigated and mathematically described not only with regard to their phase sensitivity but especially to the extent of the sensor-intrinsic phase noise. Both measurements and calculations reveal that the fundamental LOD is limited by additive phase noise due to thermal-mechanical noise of the resonator, i.e. by thermally induced random vibrations of the cantilever, and by thermal-electrical noise of the piezoelectric material. However, due to losses in the magnetic material parametric flicker phase noise arises, limiting the overall performance. In particular, it is shown that the LOD is virtually independent of the magnetic sensitivity but is solely determined by the magnetic losses. Instead of the sensitivity, the magnetic losses, represented by the material’s effective complex permeability, should be considered as the most important parameter for the further improvement of such sensors in the future. This implication is not only valid for magnetoelastic cantilevers but also applies to any type of magnetoelastic resonator. [2020-0219] [ABSTRACT FROM AUTHOR]

This work elucidates the numerical simulations carried out for the performance analysis of surface plasmon resonance (SPR)–based fiber-optic sensors using thin layers of tantalum (v) oxide (Ta2O5) and graphene in phase interrogation scheme. For this purpose, fiber-optic sensing probes with three distinct configurations have been used which include consecutive as well as individual layers of Ta2O5 and graphene over silver-coated unclad core of a silica optical fiber. The performance of sensing probes is studied in terms of the phase difference arising between TM and TE polarized components of the incident light as they propagate through the sensing region, besides their SPR responses towards varying refractive index of analyte layer, making use of the transfer matrix theory for stratified isotropic optical media in conjunction with geometrical optics. Theoretical investigations reveal that the probe having multi-layered arrangement of Ta2O5 and graphene possesses maximum sensitivity of propagating phase difference with magnitude 4.852 × 105 Deg/RIU at analyte refractive index of 1.33 in comparison to probes with individual Ta2O5 (3.731 × 105 Deg/RIU) and graphene (0.362 × 105 Deg/RIU) layers. Moreover, the design parameters of the probes have been numerically maneuvered with an aim of achieving an analyte refractive index of 1.33 in transmitted light spectrum to display the feasibility of proposed sensor in biochemical fields. The reported results unfold an innovative perspective to widen the application horizon of fiber-optic SPR sensors in phase interrogation scheme. [ABSTRACT FROM AUTHOR]

In this paper, we construct the input–output relationships of a three-mode nonlinear beam splitter (TNBS) mathematically, and a set of special solutions for the input–output equations are given. By combining two TNBSs and a phase shifter, we propose a scheme for a three-mode nonlinear interferometer (TNI) and give the input–output expression of the whole TNI. Then, we study the phase sensitivity of the TNI by giving input states and detection scheme. In addition, we also calculate the phase sensitivity of a Mach–Zehnder interferometer (MZI), SU(1,1) interferometer (SU(1,1)I) and modified Mach–Zehnder interferometer (MMZI), and we discuss the relationships of phase sensitivity between the MZI, SU(1,1)I, MMZI and TNI. Finally, in the presence of photon losses, we discuss the phase sensitivity of the four different interferometers and make detailed comparisons. It is shown that the TNI has the best robustness against photon losses under certain conditions with the same parameters. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) biosensor is widely used for its high precision and real-time analysis. In this paper, SPR biosensor based on the hybrid structure of metal–indium tin oxide (ITO)–WS2 are proposed and investigated. By optimizing the thickness of metals (Au, Cu, Ag), ITO and WS2, the reflectivity of 2.932 × 10−7 a.u and highest phase sensitivity of 1.711 × 106 deg/RIU are obtained by using Ag–ITO–WS2-dielectric structure. Compared with the traditional metal-based SPR sensor, the performance of the proposed one is improved up to ~ 25.8 times. The results show that ITO and WS2 have an important effect on enhancing SPR sensing performance. [ABSTRACT FROM AUTHOR]

Quasiperiodically forced systems are an important class of dynamical systems exhibiting quasiperiodic, strange nonchaotic, and chaotic attractors. A major concern is the identification of the parameter range in which each one of the attractors is present. In this work, based on the phase sensitivity proposed by Pikovsky and Feudel, we define a measure to quantitatively distinguish quasiperiodic attractors, strange nonchaotic attractors, and chaotic attractors. Particularly, we can determine the boundary points of these three attractors in parameter space. The reliability of this measure is verified in smooth and non-smooth systems. • The strange property of attractors in quasiperiodically forced systems is studied. • A measure is defined to quantitatively distinguish the types of attractors. • The reliability of the measure is verified in smooth and non-smooth systems. [ABSTRACT FROM AUTHOR]

In this paper, a surface plasmon resonance (SPR) sensor based on the hybrid structure of silver (Ag)-indium tin oxide (ITO)-graphene is proposed and investigated. SPR biosensors are subdivided into three kinds of structures Ag, Ag-graphene, and Ag-ITO-graphene, when carried out using their respective optimized structure parameters. According to our analysis and comparison, the ITO-assisted SPR biosensor has an optimal reflectivity of 3.587 × 10−8 and a maximum phase sensitivity of 1.707 × 106°/RIU, which shows that ITO can be employed to further enhance the SPR sensing performance even with the existence of graphene. [ABSTRACT FROM AUTHOR]

Improving the phase sensitivity of the optical fiber Sagnac sensor is very important for accurately detecting weak signals of acoustic emission. Theoretical analysis shows that the initial phase of the sensor is π under ideal conditions, and the maximum phase sensitivity is obtained when the bias phase is π/2. In this work, an experimental system was built with an aluminum alloy plate as the experimental object. The initial phase of the sensor was modulated by a Y-branch waveguide, and the fitting curve of the experimental data was in good agreement with the curve of the numerical simulation. Moreover, our experiments show there was a single value for the bias phase of π/2, which significantly deviated from the theoretical value. The results show that the greatest phase sensitivity of the sensor not only could be increased by nearly nine times through modulating the initial phase, but also could suppress the harmonic interferences in the sensing system. This study can provide a useful reference for improving the phase sensitivity of the optical fiber Sagnac AE sensor in practical applications. [ABSTRACT FROM AUTHOR]

In rodents, the progression of extrastriate areas located laterally to primary visual cortex (VI) has been assigned to a putative objectprocessing pathway (homologous to the primate ventral stream), based on anatomical considerations. Recently, we found functional support for such attribution (Tafazoli et al., 2017), by showing that this cortical progression is specialized for coding object identity despite view changes, the hallmark property of a ventral-like pathway. Here, we sought to clarify what computations are at the base of such specialization. To this aim, we performed multielectrode recordings from VI and laterolateral area LL (at the apex of the putative ventral-like hierarchy) of male adult rats, during the presentation of drifting gratings and noise movies. We found that the extent to which neuronal responses were entrained to the phase of the gratings sharply dropped from VI to LL, along with the quality of the receptive fields inferred through reverse correlation. Concomitantly, the tendency of neurons to respond to different oriented gratings increased, whereas the sharpness of orientation tuning declined. Critically, these trends are consistent with the nonlinear summation of visual inputs that is expected to take place along the ventral stream, according to the predictions of hierarchical models of ventral computations and a meta-analysis of the monkey literature. This suggests an intriguing homology between the mechanisms responsible for building up shape selectivity and transformation tolerance in the visual cortex of primates and rodents, reasserting the potential of the latter as models to investigate ventral stream functions at the circuitry level. [ABSTRACT FROM AUTHOR]

In this paper, the design and preliminary performance results of a Mach–Zehnder interferometric (MZI) strain sensor based on hollow-core photonic bandgap fiber (HC-PBG) for intrusion detection are proposed. An experiment is conducted to test the system before deployment in the field. Firstly, to judge the necessity of using the HC-PBG, an experiment is performed to compare the normalized strain responsivity (NR) of the HC-1550 and the conventional SMF-28. By interchanging the investigated optical fibers as a sensing arm of the MZI, it is possible to compare the obtained results with a conventional standard silica fiber and the HC-PBG. The experimental results show that the NR of the HC-PBG is about 3.6 – 5.3 dB better than that of the SMF depending on the frequency in the frequency range 500 Hz to 2 kHz. Secondly, we concentrate our study and measurements on the HC-1550. A simulation of intrusion detection is introduced by using the proposed interferometric fiber-optic strain sensor to detect the dynamic strain induced phase shift as a result of varying the amplitude and frequency of the input signals to a PZT tube. The investigated input signal frequencies are from 500 Hz to 2 kHz. An experiment is performed to measure the induced strain from the PZT for different input voltages and frequencies, and using the phase generated carrier (PGC) demodulation technique for extracting the measured signal information. This technique is an effective way to test the performance and the functionality of the system in lab before the field trials. Experimental results show the importance of using HC-PBG for sensing applications and the ability of the system to effectively be used for borders monitoring and securing important facilities. [ABSTRACT FROM AUTHOR]

Purpose: Acquisition of high‐resolution imaging data using multiple excitations without the sensitivity to fluctuations of the transverse magnetization phase, which is a major problem of multi‐shot MRI. Theory and Methods: The concept of superresolution MRI based on microscopic tagging is analyzed using an analogy with the optical method of structured illumination. Sinusoidal tagging is shown to provide subpixel resolution by mixing of neighboring spatial frequency (k‐space) bands. It represents a phaseless modulation added on top of the standard Fourier encoding, which allows the phase fluctuations to be discarded at an intermediate reconstruction step. Improvements are proposed to correct for tag distortions due to magnetic field inhomogeneity and to avoid the propagation of Gibbs ringing from intermediate low‐resolution images to the final image. The method was applied to diffusion‐weighted EPI. Results: Artifact‐free superresolution images can be obtained despite a finite duration of the tagging sequence and related pattern distortions by a field map based phase correction of band‐wise reconstructed images. The ringing effect present in the intermediate images can be suppressed by partial overlapping of the mixed k‐space bands in combination with an adapted filter. High‐resolution diffusion‐weighted images of the human head were obtained with a three‐shot EPI sequence despite motion‐related phase fluctuations between the shots. Conclusion: Due to its phaseless character, tagging‐based sub‐pixel encoding is an alternative to k‐space segmenting in the presence of unknown phase fluctuations, in particular those due to motion under strong diffusion gradients. Proposed improvements render the method practicable in realistic conditions. [ABSTRACT FROM AUTHOR]

We propose a multi-mode nonlinear interferometers structure by cascading several multi-mode beam splitters (MBS) and nonlinear phase shifters (NPS), in which multiple phases can be estimated simultaneously. Specially, we mainly discuss two phases estimation in a three-mode nonlinear interferometer with single photons as inputs. The phase sensitivity of the three-mode nonlinear interferometer can be discussed by the quantum Fisher information matrix (QFIM) method after the states undergo the nonlinear phase shifters, and can also be studied by classical Fisher information matrix (CFIM) method in the interferometer’s output ports. It is shown that the precision given by CFIM can achieve the bound of QFIM. Finally, we make a comparison with an optimal probe state in terms of the total variance and discuss the relationship of the total variance among three different phase estimation schemes. [ABSTRACT FROM AUTHOR]

Interferometric fiber-optic hydrophones are an important means in the field of underwater acoustic detection. The design of the hydrophone sensor head is the key technology related to its detection sensitivity. In this paper, a high-sensitivity cuboid interferometric fiber-optic hydrophone based on planar rectangular film sensing is proposed, and the sensitivity of the sensor is compared with that of the widely used air-backed mandrel hydrophone under the same conditions. The acoustic characteristic models of the two types of sensors were established by theoretical calculation and simulation analysis to obtain the theoretical pressure sensitivity. Some experiments were performed to examine the theory and design. According to the experiment results, the mean phase sensitivity of the mandrel type was −112.85 dB re 1 rad/μPa in the operating frequency range of 10–300 Hz, and that of the cuboid type was −84.50 dB re 1 rad/μPa. The latter was 28.35 dB higher than the former was. These results are useful for improving hydrophone sensitivity.

• A slow-light interferometer with a footprint as small as 1.5 mm × 4 mm is proposed. • By introducing the MKR slow light into interferometer, the phase sensitivity of the interferometer is improved. • The slow light interferometer has a larger bandwidth of slow light. • The transmission and phase sensitivity of slow-light interferometer are analyzed theoretically and experimentally. High sensitivity interferometers are key building blocks in many areas of optical and photonic devices. In this letter, we propose and experimentally demonstrate a new scheme for improving the phase sensitivity of interferometer by using slow light in a microknot resonator (MKR). The slow-light interferometer with a footprint of 1.5 mm × 4 mm is fabricated by using microfiber with a diameter of 5.6 μm. By coupling MKR to one arm of the interferometer, the slow light is introduced to enhance the phase sensitivity of the interferometer. The experimental results show that the MKR has a Q-factor of 13520, and the time delay of slow light at resonance frequency is 28 ps. The phase sensitivity of Mach-Zehnder interferometer (MZI) with slow light is 25.54 rad/THz, which is 10.4 times that of a MZI without slow light. The proposed hybrid structure has the advantages of easy fabrication, small footprint, high sensitivity and wide slow light bandwidth, allowing for potential applications in miniaturization of spectrometer and high sensitivity sensing. [ABSTRACT FROM AUTHOR]

A novel scheme for the enhancement of phase sensitivity based on a Mach–Zehnder interferometer (MZI) and intensity detection is proposed. With the input of bright entangled twin beams from four wave mixing (FWM), the phase sensitivity can beat shot noise limit (SNL) and approach Heisenberg limit. This scheme is special due to that only one of bright entangled twin beams enters into the MZI and the other one is employed for measurement. In addition, by altering the parametric strength of FWM and the implementation of maximum quantum squeezing, the optimal phase sensitivity can reach sub-SNL. Optical intensity depletion of photon detectors and internal intensity depletion of the MZI are also discussed. The scheme displays that by employing external resources, while one input of the MZI is an vacuum beam, the phase sensitivity still can beat SNL.

Highlights • Combination of double-exposure phase-shifting holography with summation of hologram series is detailed. • A software routine is proposed to use these developments. • Sensitivity and spatial resolution improvements are discussed extensively. • An experimental study is performed by using DFEH strain mapping. Abstract In this paper we discuss developments for Lorentz mode or “medium resolution” off-axis electron holography such that it is now routinely possible obtain very high sensitivity phase maps with high spatial resolution whilst maintaining a large field of view. Modifications of the usual Fourier reconstruction procedure have been used to combine series of holograms for sensitivity improvement with a phase-shifting method for doubling the spatial resolution. In the frame of these developments, specific attention is given to the phase standard deviation description and its interaction with the spatial resolution as well as the processing of reference holograms. An experimental study based on Dark-Field Electron Holography (DFEH), using a SiGe/Si multilayer epitaxy sample is compared with theory. The method’s efficiency of removing the autocorrelation term during hologram reconstruction is discussed. Software has been written in DigitalMicrograph that can be used to routinely perform these tasks. To illustrate the real improvements made using these methods we show that a strain measurement sensitivity of ± 0.025 % can be achieved with a spatial resolution of 2 nm and ± 0.13 % with a spatial resolution of 1 nm whilst maintaining a useful field of view of 300 nm. In the frame of these measurements a model of strain noise for DFEH has also been developed. [ABSTRACT FROM AUTHOR]

This article presents a novel, compact reflectarray antenna operating at 5 GHz. The array consists of two types of phasing element - square ring and complementary square ring. The complementary square ring is used for the phase values that are not covered by the single ring element. The grid size of the array is 0.281 x 0.28X at operating frequency 5 GHz that is much smaller than the conventional periodicity 0.5a * 0.51. The aim of unit cell design is to have a slower slope of the reflection phase graph without sacrificing the phase range of 360° where in general there is a trade-off between these two goals. The maximum slope in reflection phase graph obtained here is 34°/mm. The proposed array is fabricated on a low loss PTFE substrate of thickness 3.175 mm (0.0537 at 5 GHz) and illuminated by a horn antenna. Radiation pattern results show a very precise far-field beam with 3-dB beamwidth of 7° and 7.3° for two principal planes respectively. The gain of the antenna is 26 dBi at 5 GHz. [ABSTRACT FROM AUTHOR]

When excited over a periodic metamaterial lattice of gold nanoparticles (~ 100 nm), localized plasmon resonances (LPR) can be coupled by a diffraction wave propagating along the array plane, which leads to a drastic narrowing of plasmon resonance lineshapes (down to a few nm full-width-at-half-maximum) and the generation of singularities of phase of reflected light. These phenomena look very promising for the improvement of performance of plasmonic biosensors, but conditions of implementation of such diffractively coupled plasmonic resonances, also referred to as plasmonic surface lattice resonances (PSLR), are not always compatible with biosensing arrangement implying the placement of the nanoparticles between a glass substrate and a sample medium (air, water). Here, we consider conditions of excitation and properties of PSLR over arrays of glass substrate-supported single and double Au nanoparticles (~ 100–200 nm), arranged in a periodic metamaterial lattice, in direct and Attenuated Total Reflection (ATR) geometries, and assess their sensitivities to variations of refractive index (RI) of the adjacent sample dielectric medium. First, we identify medium (PSLR air , PSLR wat for air and water, respectively) and substrate (PSLR sub ) modes corresponding to the coupling of individual plasmon oscillations at medium- and substrate-related diffraction cut-off edges. We show that spectral sensitivity of medium modes to RI variations is determined by the lattice periodicity in both direct and ATR geometries (~ 320 nm per RIU change in our case), while substrate mode demonstrates much lower sensitivity. We also show that phase sensitivity of PSLR can exceed 10 5 degrees of phase shift per RIU change and thus outperform the relevant parameter for all other plasmonic sensor counterparts. We finally demonstrate the applicability of surface lattice resonances in plasmonic metamaterial arrays to biosensing using standard streptavidin-biotin affinity model. Combining advantages of nanoscale architectures, including drastic concentration of electric field, possibility of manipulation at the nanoscale etc, and high phase and spectral sensitivities, PSLRs promise the advancement of current state-of-the-art plasmonic biosensing technology toward single molecule label-free detection. [ABSTRACT FROM AUTHOR]

Laue microdiffraction is used to determine the full elastic strain tensor of the γ and γ′ phases in grains of a nickel-based superalloy with a coarse-grained microstructure. A `rainbow' filter and an energy dispersive point detector are employed to measure the energy of Bragg reflections. For the two techniques, an uncertainty of ±2.5 × 10−3 Å is obtained for the undetermined crystal lattice parameter. Our measurements show that the filter method provides better confidence, energy resolution, accuracy and acquisition time. The sensitivity of each method with respect to the γ-γ′ lattice mismatch is demonstrated with measurements in samples with average precipitate sizes of 200 and 2000 nm. For the 200 nm precipitate size, the lattice mismatch is less than 2 × 10−3 Å and the dilatational strains are close to ±1.5 × 10−3 depending on the considered phase. For the 2000 nm precipitate size, the lattice mismatch is close to 8 × 10−3 Å and almost no elastic strain occurs in the microstructure. [ABSTRACT FROM AUTHOR]