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Silicon carbide fiber reinforced silicon carbide ceramic matrix composite (CMC SiC f /SiC) has the advantages of high temperature resistance, corrosion resistance, high strength, low density, and oxidation resistance. It is a high-performance advanced material in aerospace, energy and other fields. However, due to its high hardness, brittleness and anisotropy of fiber structure, the research on application-oriented high-quality processing technology has become a hot issue. In this paper, a new process of rotational thirteen-beam coupling nanosecond laser processing of CMC-SiC f /SiC was studied. The rotational thirteen-beam coupling ablation experiments were carried out on CMC-SiC f /SiC workpiece. A laser beam is divided into thirteen beams and rotated around the beam center by using a beam splitter element. The morphology, structure and composition of ablation holes at different speeds were observed and analyzed by laser confocal microscope, scanning electron microscope, and X-ray energy dispersive spectrometer. It is found that the characteristics of rotational beam coupling have a significant effect on the laser ablation morphologies. The results show that the ablation region of CMC-SiC f /SiC is elliptical due to the fast heat transfer of fibers. The energy density distribution of the waist section of the Gaussian like beam after beam coupling is similar to the "W" shape, and the central energy is lower than the surrounding energy, and the ablation holes also show a similar "W" shape. With the increase of rotational speed, the hole depth first decreased and then increased, the hole diameter and roundness first increased and then decreased, and the hole section was "W" shaped. The ablation area can be divided into five parts: the white granular SiO 2 solid coverage area, the recast layer, the lower recast layer, the molten layer, and the heat affected zone. The rotational characteristics will make the reaction intensity of the whole ablation area more uniform in the circumferential direction. The formation mechanism and element distribution of each part were explored. The research work in this paper will provide a new technical way for the high-performance application of CMC-SiC f /SiC. [ABSTRACT FROM AUTHOR]

In recent years, handheld and portable terahertz instruments have been in rapid development for various applications ranging from non-destructive testing to biomedical imaging and sensing. For instance, we have deployed our Portable Handheld Spectral Reflection (PHASR) Scanners for in vivo full-spectroscopic imaging of skin burns in large animal models in operating room settings. In this paper, we debut the polarimetric version of the PHASR Scanner, and describe a generalized calibration technique to map the spatial and spectral dependence of the Jones matrix of an imaging scanner across its field of view. Our design is based on placement of two orthogonal photoconductive antenna (PCA) detectors separated by a polarizing beam splitter in the PHASR Scanner housing. We show that as few as three independent measurements of a well-characterized polarimetric calibration target are sufficient to determine the polarization state of the incident beam at the sample location, as well as to extract the Jones propagation matrix from the sample location to the detectors. We have tested the accuracy of our scanner by validating polarimetric measurements obtained from a birefringent crystal rotated to various angles, as compared to the theoretically predicted response of the sample. This new version of our PHASR scanner can be used for high-speed imaging and investigation of heterogeneity of polarization-sensitive samples in the field. [ABSTRACT FROM AUTHOR]

Quasi-continuous-phase metasurfaces overcome the side effects imposed by high-order diffraction on imaging and can impart optical parameters such as amplitude, phase, polarization, and frequency to incident light at sub-wavelength scales with high efficiency. Structured-light three-dimensional (3D) imaging is a hot topic in the field of 3D imaging because of its advantages of low computation cost, high imaging accuracy, fast imaging speed, and cost-effectiveness. Structured-light 3D imaging requires uniform diffractive optical elements (DOEs), which could be realized by quasi-continuous-phase metasurfaces. In this paper, we design a quasi-continuous-phase metasurface beam splitter through a vector iterative Fourier transform algorithm and utilize this device to realize structured-light 3D imaging of a target object with subsequent target reconstruction. A structured-light 3D imaging system is then experimentally implemented by combining the fabricated quasi-continuous-phase metasurface illuminated by the vertical-cavity surface-emitting laser and a binocular recognition system, which eventually provides a new technological path for the 3D imaging field. [ABSTRACT FROM AUTHOR]

In this paper, we present a distal-scanning common path probe for optical coherence tomography (OCT) equipped with a hollow ultrasonic motor and a simple and specially designed beam-splitter. This novel probe proves to be able to effectively circumvent polarization and dispersion mismatch caused by fiber motion and is more robust to a variety of interfering factors during the imaging process, experimentally compared to a conventional noncommon path probe. Furthermore, our design counteracts the attenuation of backscattering with depth and the fall-off of the signal, resulting in a more balanced signal range and greater imaging depth. Spectral-domain OCT imaging of phantom and biological tissue is also demonstrated with a sensitivity of ∼ 1 0 0 dB and a lateral resolution of ∼ 3 μ m. This low-cost probe offers simplified system configuration and excellent robustness, and is therefore particularly suitable for clinical diagnosis as one-off medical apparatus. [ABSTRACT FROM AUTHOR]

Coherent microwave-to-optical conversion is crucial for transferring quantum information generated in the microwave domain to optical frequencies, where propagation losses can be minimized. Coherent, atom-based transducers have shown rapid progress in recent years. This paper reports an experimental demonstration of coherent microwave-to-optical conversion that maps a microwave signal to a large, tunable 550(30) MHz range of optical frequencies using room-temperature 87Rb atoms. The inhomogeneous Doppler broadening of the atomic vapor advantageously supports the tunability of an input microwave channel to any optical frequency channel within the Doppler width, along with the simultaneous conversion of a multi-channel input microwave field to corresponding optical channels. In addition, we demonstrate phase-correlated amplitude control of select channels, providing an analog to a frequency domain beam splitter across five orders of magnitude in frequency. With these capabilities, neutral atomic systems may also be effective quantum processors for quantum information encoded in frequency-bin qubits. Coherent microwave-to-optical conversion is crucial for networking physically separated quantum devices. This paper demonstrates coherent conversion of microwaves to a wide, tuneable optical frequency range using room-temperature Rb atoms, supporting frequency division multiplexing and coherent frequency channel control. [ABSTRACT FROM AUTHOR]

Impedance theory has become a favorite method for metasurface design as it allows perfect control of wave properties. However, its functionality is strongly limited by the condition of strict continuity of normal power flow. In this paper, it is shown that acoustic impedance theory can be generalized under the integral equivalence principle without imposing the continuity of power flow. Equivalent non-local power flow transmission is instead realized through local design of metasurface unit cells that are characterized by a passive, asymmetric impedance matrix. Based on this strategy, a beam splitter loosely respecting local power flow is designed and demonstrated experimentally. It is concluded that arbitrary wave fields can be connected through arbitrarily shaped boundaries, i.e. transformed into one another. Generalized impedance metasurface theory is expected to extend the possible design of metasurfaces and the manipulation of acoustic waves. Impedance theory grants insight to design metasurfaces for controlling acoustic fields, but such theory imposes great limitation on boundary conditions. The authors propose a generalized acoustic impedance theory connecting arbitrarily conservative acoustic fields, and design a beam splitter as an example of power flow processing. [ABSTRACT FROM AUTHOR]

Recent literature has shown, theoretically as well as experimentally, that while a beam splitter does not split a single photon, it nonetheless divides the electromagnetic wave into transmitted and reflected, with both containing energies. This implies the existence of a spacetime of pure electromagnetic waves of energies but without particles; also, it prompts the question on how much energy a photon loses after coming out of a beam splitter, which impacts on interferometry and hence quantum communication. This paper shows that, by Gauss divergence theorem, the gravitational force inside an electromagnetic wave ball results in a point energy that is three times as the wave energy; thus, a 50/50 beam splitter is to cause a photon to lose half of a quarter, or 1/8, of its initial wave energy. [ABSTRACT FROM AUTHOR]

Metasurfaces, composed of micro-nano-structured planar materials, offer highly tunable control over incident light and find significant applications in imaging, navigation, and sensing. However, highly efficient polarization devices are scarce for the extended shortwave infrared (ESWIR) range (1.7~2.5 μm). This paper proposes and demonstrates a highly efficient all-dielectric diatomic metasurface composed of single-crystalline Si nanocylinders and nanocubes on SiO2. This metasurface can serve as a nanoscale linear polarizer for generating polarization-angle-controllable linearly polarized light. At the wavelength of 2172 nm, the maximum transmission efficiency, extinction ratio, and linear polarization degree can reach 93.43%, 45.06 dB, and 0.9973, respectively. Moreover, a nonpolarizing beam splitter (NPBS) was designed and deduced theoretically based on this polarizer, which can achieve a splitting angle of ±13.18° and a phase difference of π. This beam splitter can be equivalently represented as an integration of a linear polarizer with controllable polarization angles and an NPBS with one-bit phase modulation. It is envisaged that through further design optimization, the phase tuning range of the metasurface can be expanded, allowing for the extension of the operational wavelength into the mid-wave infrared range, and the splitting angle is adjustable. Moreover, it can be utilized for integrated polarization detectors and be a potential application for optical digital encoding metasurfaces. [ABSTRACT FROM AUTHOR]

For around five decades, physicists have been experimenting with single quanta such as single photons. Insofar as the practised ensemble reasoning has become obsolete for the interpretation of these experiments, the non-classical intrinsic probabilistic nature of quantum theory has gained increased importance. One of the most important exclusive features of quantum physics is the undeniable existence of the superposition of states, even for single quantum objects. One known example of this effect is entanglement. In this paper, two classically contradictory phenomena are combined to one single experiment. This experiment incontestably shows that a single photon incident on an optical beam splitter can either be reflected or transmitted. The almost complete absence of coincident clicks of two photodetectors demonstrates that these two output states are incompatible. However, when combining these states using two mirrors, we can observe interference patterns in the counting rate of the single photon detector. The only explanation for this is that the two incompatible output states are prepared and kept simultaneously—a typical consequence of a quantum superposition of states. (Semi-)classical physical concepts fail here, and a full quantum concept is predestined to explain the complementary experimental outcomes for the quantum optical "non-waves" called single photons. In this paper, we intend to demonstrate that a true quantum physical key experiment ("true" in the sense that it cannot be explained by any classical physical concept), when combined with full quantum reasoning (probability, superposition and interference), influences students' readiness to use quantum elements for interpretation. [ABSTRACT FROM AUTHOR]

In this paper, a controllable hybrid plasmonic integrated circuit (CHPIC) composed of hybrid plasmonic waveguide (HPW)-based rhombic nano-antenna, polarization beam splitter, coupler, filter, and sensor has been designed and investigated for the first time. In order to control the power into a corresponding input port, a graphene-based 1 × 3 power splitter with switchable output has been exploited. The functionality of each device has been studied comprehensively based on the finite element method and the advantages over state-of-the-art have been compared. Moreover, the effect of connection of CHPIC to the photonic and plasmonic waveguides has been studied to exhibit the capability of variety excitation methods of the CHPIC. Furthermore, the performance of the proposed CHPIC connected to inter/intra wireless transmission links has been investigated. The wireless transmission link consists of two HPW-based nano-antennas as transmitter and receiver with the maximum gain and directivity of 10 dB and 10.2 dBi, respectively, at 193.5 THz. The suggested CHPIC can be used for applications such as optical wireless communication and inter/intra-chip optical interconnects. [ABSTRACT FROM AUTHOR]

This paper deals with the covariance matrix (CM) of two-mode Gaussian states, which, together with the mean vector, fully describes these states. In the two-mode states, the (ordinary) CM is a real symmetric matrix of order 4; therefore, it depends on 10 real variables. However, there is a very efficient representation of the CM called the standard form (SF) that reduces the degrees of freedom to four real variables, while preserving all the relevant information on the state. The SF can be easily evaluated using a set of symplectic invariants. The paper starts from the SF, introducing an architecture that implements with primitive components the given two-mode Gaussian state having the CM with the SF. The architecture consists of a beam splitter, followed by the parallel set of two single–mode real squeezers, followed by another beam splitter. The advantage of this architecture is that it gives a precise non-redundant physical meaning of the generation of the Gaussian state. Essentially, all the relevant information is contained in this simple architecture. [ABSTRACT FROM AUTHOR]

In this paper, we present a coherent feedback loop scheme to enhance the magnon–photon–phonon entanglement in cavity magnomechanics. We provide a proof that the steady state and dynamical state of the system form a genuine tripartite entanglement state. To quantify the entanglement in the bipartite subsystem and the genuine tripartite entanglement, we use the logarithmic negativity and the minimum residual contangle, respectively, in both the steady and dynamical regimes. We demonstrate the feasibility of our proposal by implementing it with experimentally realizable parameters to achieve the tripartite entanglement. We also show that the entanglement can be significantly improved with coherent feedback by appropriately tuning the reflective parameter of the beam splitter and that it is resistant to environmental thermalization. Our findings pave the way for enhancing entanglement in magnon–photon–phonon systems and may have potential applications in quantum information. [ABSTRACT FROM AUTHOR]

Usually in quantum optics, the theory of large- and small-scale waveguide beam splitters is the same. In this paper, it is shown that the theory of the nanoscale waveguide beamsplitter has a significant difference from a similar device, but of a larger scale. It is shown that the previously known theory of the waveguide beam splitter is a particular case of the theory presented here. The wave function at the output ports of the nanoscale beam splitter is analyzed. The results obtained are sensitive to the size of the beam splitter, the coupling parameter of the two waveguides, and the degree of nonmonochromaticity of the photons entering the first and second ports of the beam splitter. The results are important for quantum technologies using a nanosized beam splitter. [ABSTRACT FROM AUTHOR]

This paper proposes a perimeter detection scheme based on the quantum physical properties of photons. Existing perimeter intrusion detection schemes, if using light, rely on the classical properties of light only. Our quantum sensor network uses the quantum property of spatial superposition of photons, meaning that a photon can simultaneously follow two different paths after going through a beam splitter. Using multiple Mach–Zehnder interferometers, an entire web of paths can be generated, such that one single photon occupies them all. If an intruder violates this web in some arbitrary point, the entire photon superposition is destroyed, the photon does not self-interfere any more and this event is detected by measurements. For one single photon, the intruder detection probability is limited theoretically but can be increased arbitrarily with the usage of a sequence of photons. We show both theoretical bounds as well as practical results of the proposed schemes. The practical results are obtained by simulation experiments on IBM Quantum platforms. The benefits of our quantum approach are: low power, invisibility to potential intruders, scalability and easy practical implementation. [ABSTRACT FROM AUTHOR]

In this paper, multispectral pedestrian detection is mainly discussed, which can contribute to assigning human-aware properties to automated forklifts to prevent accidents, such as collisions, at an early stage. Since there was no multispectral pedestrian detection dataset in an intralogistics domain, we collected a dataset; the dataset employs a method that aligns image pairs with different domains, i.e. RGB and thermal, without the use of a cumbersome device such as a beam splitter, but rather by exploiting the disparity between RGB sensors and camera geometry. In addition, we propose a multispectral pedestrian detector called SSD 2.5D that can not only detect pedestrians but also estimate the distance between an automated forklift and workers. In extensive experiments, the performance of detection and centroid localization is validated with respect to evaluation metrics used in the driving car domain but with distinct categories, such as hazardous zone and warning zone, to make it more applicable to the intralogistics domain. [ABSTRACT FROM AUTHOR]

Beam splitters are vital components in several optical systems. It is highly desirable, and compact beam splitters with ultra-broadband performances, high efficiencies, and large split angles are still being sought. In this paper, we demonstrate and numerically investigate an ultra-broadband and highly efficient optical beam splitter based on a quasi-continuous metasurface. The proposed design is constructed of quasi-continuous triangle-shaped gallium phosphide nanoantennas on a silica substrate. The simple structure can achieve a conversion efficiency and an anomalous transmission intensity above 90% and 0.8 covering the wavelength range of 1537–1826 nm, respectively. The maximum beam split angle in the operating bandwidth reaches 131.84° at the wavelength of 1826 nm. Particularly, the operating bandwidth is still as high as 125 nm with the anomalous transmission intensity above 0.92 and the conversion efficiency exceeding 99%. Moreover, the results show that the performance of the metasurface-based optical beam splitter can be further enhanced by optimizing structural parameters. We also demonstrate the adjustability of the beam splitter by adding refractive index (RI) materials on the surface of the device. The results show that the incident plane wave can be divided into three beams with intensity adjustability. The presented metasurface is very promising in the fields of multiplexers, interferometers, and optical communications, owing to its advantages of ultra-broadband, highly efficient, and large split angle simultaneously. [ABSTRACT FROM AUTHOR]

Metasurfaces with both multifunctionality and tunability hold great application potential in next-generation optical devices. In this paper, we propose a stretchable metasurface composed of arrays of identical dielectric rectangular resonators embedded in the polydimethylsiloxane (PDMS) substrate. It is shown that the metasurface possesses three functions at the operating wavelength of 532 nm. The switching of functions can be implemented by changing the period Px of the metasurface, induced by stretching the PDMS substrate along the x-direction. When the period Px is less than the operating wavelength of 532 nm, the behavior of metasurface can switch between transmissive window and reflective mirror. When the period Px of the metasurface varies from 532 nm to 700 nm, the metasurface act as a dynamic equal-power beam splitter with conversion efficiency higher than 90%, and the corresponding splitting angle can be adjusted from 90° to around 49.5°. Moreover, we achieve the switching of transmissive window/reflective mirror/split-ratio-variable splitter based on the metasurface consisting of arrays of identical L-shaped resonators embedded in the PDMS substrate. [ABSTRACT FROM AUTHOR]

Quantum Gaussian states play a fundamental role in quantum communications and in quantum information. This paper deals with the implementation of multimode, and particularly of two-mode Gaussian unitaries and Gaussian states with primitive components (phase shifters, single-mode real squeezers, displacements, and beam splitters). The architecture thus obtained allows one to obtain an insight into the physical meaning of each variable involved. Moreover, following the implementation architecture, it is possible to formulate an easy algebra (radical free) for the main operations and transformations of Gaussian states. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical study into the use of optical systems for quantum computation. The study results pertain to quantum sampling and quantum communication and provide a basis for further research and the development of a physical implementation. We propose an optical superstructure that can implement specific computation processes and algorithms. The superstructure is composed of nonlinear optical units, such as beta barium borate crystals. The units are positioned in series, powered by a pulse laser pump, and culminate in a beam splitter that generates the output state of a number of entangled photon pairs. Computation is achieved by entanglement propagation via beam splitters and adjustable phase shifters, which set related parameters. Demonstrating a two-component case, we show how a series of cosine-based components can be implemented. The obtained results open a broad front for future research. Future work should investigate the construction of a quantum optimizer using quantum sampling methods and also investigate high-precision temporal voltage measurement, which is a key procedure for the construction of high-fidelity devices. [ABSTRACT FROM AUTHOR]

This paper proposes a new optical configuration for a two-axis surface encoder that can measure the in-plane (X-axis) and out-of-plane (Z-axis) displacements of a positioning stage. The two-axis surface encoder is composed of a scale grating and a sensor head. A transparent grating is employed in the sensor head for measurement of the Z-directional displacement of the scale grating based on the Fizeau-type measurement method; a reference beam reflected from the transparent grating and the zeroth-order diffracted beam from the scale grating are superimposed to generate an interference signal. A pair of prisms and a beam splitter are also employed in the sensor head, so that the positive and negative first-order diffracted beams can be superimposed over a long working distance to generate an interference signal for measurement of the X-directional displacement of the scale grating. Focusing on the new, extended Z-directional measurement mechanism, proof-of-principle experiments were carried out to verify the feasibility of the proposed optical configuration for the surface encoder that can measure the uni-directional displacements of a scale grating along the X- and Z-axis. Experimental results from the developed optical configuration demonstrated the achievement of a Z-directional measuring range of ±1.5 mm. [ABSTRACT FROM AUTHOR]

The column-averaged dry-air mole fractions of CO2 (XCO2), CH4 (XCH4) and CO (XCO) have been measured with a Bruker IFS 125HR Fourier-transform infrared (FTIR) spectrometer at Xianghe (39.75 ∘ N, 116.96 ∘ E, north China) since June 2018. This paper presents the site, the characteristics of the FTIR system and the measurements. The instrumental setup follows the guidelines of the Total Carbon Column Observing Network (TCCON): the near-infrared spectra are recorded by an InGaAs detector together with a CaF2 beam splitter, and the HCl cell measurements are recorded regularly to derive the instrument line shape (ILS) showing that the instrument is correctly aligned. The TCCON standard retrieval code (GGG2014) is applied to retrieve XCO2 , XCH4 and XCO. The resulting time series between June 2018 and July 2019 are presented, and the observed seasonal cycles and day-to-day variations in XCO2 , XCH4 and XCO at Xianghe are discussed. In addition, the paper shows comparisons between the data products retrieved from the FTIR measurements at Xianghe and co-located Orbiting Carbon Observatory-2 (OCO-2) and Tropospheric Monitoring Instrument (TROPOMI) satellite observations. The comparison results appear consistent with validation results obtained at TCCON sites for XCO2 and XCH4 , while for XCO they highlight the occurrence of frequent high-pollution events. As Xianghe lies in a polluted area in north China where there are currently no TCCON sites, this site can fill the TCCON gap in this region and expand the global coverage of the TCCON measurements. The Xianghe FTIR XCO2 , XCH4 and XCO data can be obtained at 10.18758/71021049. [ABSTRACT FROM AUTHOR]

Photonic integrated circuits (PIC) provide promising functionalities to significantly reduce the size and costs of optical coherence tomography (OCT) systems. This paper presents an imaging platform operating at a center wavelength of 830 nm for ophthalmic application using PIC-based swept source OCT. An on-chip Mach–Zehnder interferometer (MZI) configuration, which comprises an input power splitter, polarization beam splitters in the sample and the reference arm, and a 50/50 coupler for signal interference represents the core element of the system with a footprint of only (12 × 5) mm 2 . The system achieves 94 dB imaging sensitivity with 750 μ W on the sample, 50 kHz imaging speed and 5.5 μ m axial resolution (in soft tissue). With this setup, in vivo human retinal imaging of healthy subjects was performed producing B-scans, three-dimensional renderings as well as OCT angiography. These promising results are significant prerequisites for further integration of optical and electronic building blocks on a single swept source-OCT PIC. [ABSTRACT FROM AUTHOR]

It is well known that a beam splitter (BS) can be used as a source of photon quantum entanglement. This is due to the fact that the statistics of photons changes at the output ports of the BS. Usually, quantum entanglement and photon statistics take into account the constancy of the reflection coefficient R or the transmission coefficient T of the BS, where R + T = 1 . It has recently been shown that if BS is used in the form of coupled waveguides, the coefficients R and T will depend on the photon frequencies. In this paper, it is shown that the quantum entanglement and statistics of photons at the output ports of a BS can change significantly if a BS is used in the form of coupled waveguides, where the coefficients R and T are frequency-dependent. [ABSTRACT FROM AUTHOR]

In this paper, we study the optical trapping of anti-reflection core-shell microspheres by regular Gaussian beam and several structured beams including radially polarized Gaussian, petal, and hard-aperture-truncated circular Airy beams. We show that using an appropriate anti-reflection core-shell microsphere for the optical trapping by several structured light beams can dramatically enhance the strength of the trap compared to the trapping by the common Gaussian beam. The optimal core-shell thickness ratio that minimizes the scattering force is obtained for polystyrene-silica and anatase-amorphous titania microspheres, such that the core-shells act as anti-reflection coated microspheres. We show that the trapping strength of the anti-reflection coated microparticles trapped by the common Gaussian beam is enhanced up to 2-fold compared to that of trapped uncoated microparticles, while the trapping of anti-reflection coated microparticles, by the radially polarized beam, is strengthened up to 4-fold in comparison to that of the trapped uncoated microparticles by the Gaussian beam. Our results indicate that for anatase-amorphous titania microparticles highest trap strength is obtained by radially polarized beam, while for the polystyrene-silica microparticles, the strongest trapping is achieved by the petal beam. [ABSTRACT FROM AUTHOR]

The optical path calibration process using a laser interferometer is time-consuming and tedious, requiring repeated adjustment and experienced operators, leading to a significant reduction in measuring efficiency. A novel optical path calibration process of the linear axis of a three-axis machine tool using a Renishaw XL-80 laser interferometer is proposed in this paper. The homogeneous coordinate transformation error model of the measured axis is established. Using the established error model, only the initial distance from the laser transmitter to the beam splitter and the initial distance from the beam splitter to the linear mirror are required to accurately calibrate the laser beam. The relationship between the fixed distance from the center of the light target to the quarter point on the edge of the light target and the movement distance of the measured axis are obtained. Eight deviations of the optical path affected by the laser transmitter, the beam splitter and the linear mirror are solved. Calibrations based on the deviations can be achieved by adjusting the positions and orientations of the laser interferometer components, leading to a rapid and accurate calibration method for measuring the optical paths. [ABSTRACT FROM AUTHOR]

In this paper, the analysis of the quantum properties of cavity light produced by a coherently driven nondegenerate three-level laser in a closed cavity and coupled to a two-mode vacuum reservoir, is presented. Normal ordering of the noise operators associated with the vacuum reservoir is considered. Applying the solutions of the equations of evolution for the expectation values of the atomic operators and the quantum Langavin equations for the cavity mode operators, the quadrature squeezing, entanglement amplification, and the normalized second-order correlation function of the cavity radiation are obtained. The three-level laser generates squeezed light under certain conditions, with maximum intracavity squeezing being 43% below the vacuum-state level. Moreover, it is found that the photon numbers of a two-mode light beams are correlated. [ABSTRACT FROM AUTHOR]

This paper presents a novel experimental approach for confirming that spherical mirror of a laser tracking system can reduce the influences of rotation errors of gimbal mount axes on the measurement accuracy. By simplifying the optical system model of laser tracking system based on spherical mirror, we can easily extract the laser ranging measurement error caused by rotation errors of gimbal mount axes with the positions of spherical mirror, biconvex lens, cat's eye reflector, and measuring beam. The motions of polarization beam splitter and biconvex lens along the optical axis and vertical direction of optical axis are driven by error motions of gimbal mount axes. In order to simplify the experimental process, the motion of biconvex lens is substituted by the motion of spherical mirror according to the principle of relative motion. The laser ranging measurement error caused by the rotation errors of gimbal mount axes could be recorded in the readings of laser interferometer. The experimental results showed that the laser ranging measurement error caused by rotation errors was less than 0.1 μm if radial error motion and axial error motion were within ±10 μμurement accuracy of the laser tracking system. [ABSTRACT FROM AUTHOR]

This paper describes the in-flight calibration of the polarization response of the SCIAMACHY polarization measurement devices (PMDs) and a selected region of its science channels. With the lack of polarized calibration sources it is not possible to obtain such a calibration from dedicated calibration measurements. Instead, the earthshine itself, together with a simplified radiative transfer model (RTM), is used to derive time-dependent and measurement-configuration-dependent polarization sensitivities. The results are compared to an instrument model that describes the degradation of the instrument as a result of a slow buildup of contaminant layers on its elevation and azimuth scan mirrors. This comparison reveals significant differences between the model prediction and the data, suggesting an unforeseen change between on-ground and in-flight calibration in at least one of the polarization-sensitive components of the optical bench. The possibility of mechanisms other than scan mirror contamination contributing to the degradation of the instrument will be discussed. The data are consistent with a polarization phase shift occurring in the beam split prism used to divert the light coming from the telescope to the different channels and polarization measurement devices. The extension of the instrument degradation model with a linear retarder enables the determination of the relevant parameters to describe this phase shift and ultimately results in a significant improvement of the polarization measurements as well as the polarization response correction of measured radiances. [ABSTRACT FROM AUTHOR]

This paper describes the study of deformation of reinforced concrete. A mathematical model for the interaction of reinforcement with concrete, based on the introduction of a contact layer, whose mechanical characteristics are determined from the experimental data, is developed. The limiting state of concrete is described using the Drucker-Prager theory and the fracture criterion with respect to maximum plastic deformations. A series of problems of the theory of reinforced concrete are solved: stretching of concrete from a central-reinforced prism and pre-stressing of concrete. It is shown that the results of the calculations are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Shifts of center wavelengths (CWLs) and related changes of full-widths at half-maximums (FWHMs) occur during in-flight data acquisitions of push-broom imaging spectrometers such as the airborne prism experiment (APEX). Combined with the spectrally changing properties of the dichroic coating that acts as a beam splitter between the visible and near infrared (VNIR) as well as the short-wave infrared (SWIR) channels, these shifts affect both the spectral and radiometric accuracies of the spectrometer data, and hence the accuracy of higher level products. In this paper, two independent standards, i.e., atmospheric absorption features as well as features of the standard reference material filter built in the APEX in-flight characterization facility, are used in a complementary way to improve in-flight spectral calibration. The CWL shift and FWHM change for each detector element are simultaneously detected by using spectrum-matching and surface fitting techniques under constraints from pregenerated shift realizations. Subsequently, the APEX spectroradiometric response model is improved in the aspect of spectral resolution by using performance parameters of optics and detector modules. The radiometric gain and offset for each detector element are corrected according to the detected CWLs and FWHMs, as well as the improved APEX response model. Compared with the spectral and radiometric parameters acquired during laboratory calibration, the detected CWLs and FWHMs promote the accuracy of the atmospheric feature positions in the SWIR channel by 10 nm, whereas the corrected gains and offsets reduce the radiance deviation in the spectral regions 375–550 nm and 950–1080 nm both by 70% on average. [ABSTRACT FROM PUBLISHER]

A stochastic flow network is a directed graph with incoming edges (inputs) and outgoing edges (outputs), tokens enter through the input edges, travel stochastically in the network, and can exit the network through the output edges. Each node in the network is a splitter, namely, a token can enter a node through an incoming edge and exit on one of the output edges according to a predefined probability distribution. Stochastic flow networks can be easily implemented by beam splitters, or by DNA-based chemical reactions, with promising applications in optical computing, molecular computing and stochastic computing. In this paper, we address a fundamental synthesis question: Given a finite set of possible splitters and an arbitrary rational probability distribution, design a stochastic flow network, such that every token that enters the input edge will exit the outputs with the prescribed probability distribution. The problem of probability transformation dates back to von Neumann’s 1951 work and was followed, among others, by Knuth and Yao in 1976. Most existing works have been focusing on the “simulation” of target distributions. In this paper, we design optimal-sized stochastic flow networks for “synthesizing” target distributions. It shows that when each splitter has two outgoing edges and is unbiased, an arbitrary rational probability a \over b with a \leq b \leq 2^n can be realized by a stochastic flow network of size n that is optimal. Compared to the other stochastic systems, feedback (cycles in networks) strongly improves the expressibility of stochastic flow networks. [ABSTRACT FROM AUTHOR]

This paper considered the technology of electron beam welding with beam splitting. It assesses the possible application of the dynamic positioning of the electron beam in welding the aluminum alloy AlMg6. The beam is split into three and this is known as multipool welding. To study the effect of the split beam parameters on the geometric characteristics of welds, we performed a series of experiments with a three-level planning matrix. Using regression analysis, we obtained the dependences of weld depth, width, aspect ratios, and completeness of penetration on the main parameters of the welding process with splitting (the beam current, the welding speed, the beam exposure time at each point, and the distances between the points). We present an analysis of the obtained dependences. The criteria for characterizing the formation of defect-free welds are defined. We propose a method to determine the optimal modes of electron beam welding with splitting for aluminum alloys using monograms. [ABSTRACT FROM AUTHOR]

This article presents a review on the research and development of spectral beam splitting concentrated photovoltaic/thermal (SBS CPVT) hybrid solar systems. The investigations on the SBS CPVT hybrid technologies had begun in the 1980s and were aimed at complete utilization of the solar irradiation over the whole solar spectrum using both PV cells and thermal absorbers. Several different SBS approaches were employed to achieve better conversion efficiencies, including the interference filter, liquid absorptive filter, holographic filter, luminescent filter, diffractive filter, combined interference and liquid absorptive filter, combined liquid and solid absorptive filter, and photovoltaics itself as a solid absorptive filter. The SBS CPVT systems were proposed or assembled in various system configurations for numerous purposes, such as domestic hot water, thermochemical reaction, hydrogen production, or even power generation. These researches and developments are comprehensively reviewed in this article, and the advantages and disadvantages of different SBS methods are presented and concluded. This paper also aims to provide a global point of view on research trends, market potential, technical obstacles, and the future work required for the development of SBS CPVT technology. [ABSTRACT FROM AUTHOR]

The position of the optical beam on an optical detector array is an important parameter for optimal decoding in free-space optical communication systems; thus, its accurate estimation is essential. In this paper, the performance of three estimators (maximum likelihood, center of gravity, and template matching) for the estimation of center of the beam on a detector array is compared in terms of mean square error and complexity. Simulation results show that the maximum likelihood estimate achieves the lowest mean square error and especially performs significantly better than center of gravity under poor signal-to-noise ratio conditions, for both the continuous and discrete/quantized arrays. [ABSTRACT FROM AUTHOR]

Abstract: The three-phase composite model (TPM) is analyzed from the viewpoint of the asymptotic homogenization method. It is shown that such an asymptotic process can be constructed that the three-phase model will represent a zero-order approximation. Therefore the present paper presents a mathematical asymptotic justification of the TPM technique. Further more, it is shown that the TPM approach provides a sufficiently accurate solution of the unit cell local problem arising in the asymptotic homogenization for periodic composite materials with cubic inclusions with arbitrary properties. The same conclusion is proved for the unidirectional fiber-reinforced composites in the cases of parallelepiped inclusions and rectangular periodic structure. The multi-point Padé approximants are used in the present paper in order to evaluate the accuracy of three-phase models in the cases of small and large inclusions, and to derive the estimations for the effective properties of composite materials. [Copyright &y& Elsevier]

Spectral beam splitting of sunlight can improve the efficiency of solar receivers. Hybrid photovoltaic–thermal receivers designed for the concurrent generation of high grade heat and electricity can benefit considerably from this approach. In this paper, we introduce a novel method for filtering sunlight for high temperature hybrid solar receivers employed in linear solar concentrators. In this method, semiconductor doped glass is combined with propylene glycol to act simultaneously as the heat transfer fluid and a band pass filter for the optimal wavelength band, 700–1100 nm, required by silicon (Si) solar cells. Ray tracing and experimental analysis of the proposed design has shown that this filtering method directs 29% of the incoming concentrated solar spectrum to the silicon cells in the receiver with the remainder absorbed as heat. This means that 77% of the light in the optimal spectral band is effectively collected by the solar cells. The cell efficiency under this band can reach 26% in theory. The results demonstrate the potential for a simpler spectral filtering mechanism that is suitable for concentrating hybrid solar receivers. [ABSTRACT FROM AUTHOR]

In this paper, a new linearized split Bregman iterative algorithm is proposed for sparse-view X-ray computed tomography, which can avoid solving a large-scale and unstructured linear system in each iteration. Remarkably, our method can be generalized to efficiently resolve some other image processing and analysis models, for instance, the robust compressed sensing, the total variation- ℓ 1 , and the ℓ 1 – ℓ 1 . We also give rigorous proofs for the convergence of the proposed method under appropriate conditions for the aforementioned problems. Experimental results demonstrate that our algorithm has better performance in terms of reconstruction quality, effectiveness and robustness, compared with some other methods (e.g. gradient-flow-based semi-implicit finite element method, split Bregman, etc.) for the robust image reconstruction in sparse-view X-ray computed tomography. [ABSTRACT FROM AUTHOR]

In this paper, a novel method of a subwavelength binary simple periodic rectangular structure is presented to realize even beam splitting by combining the rigorous couple-wave analysis with the genetic algorithm. Several even splitters in the terahertz region were designed and one of the silicon-based beam splitters designed to separate one incident beam into four emergent beams has total efficiency up to 92.23 %. Zero-order diffraction efficiency was reduced to less than 0.192 % and the error of uniformity decreased to 6.51 × 10. These results break the limitation of even beam splitting based on the traditional scalar theory. In addition, the effects of the incident angle, wavelength, as well as the polarizing angle on the diffraction efficiency and uniformity were also investigated. [ABSTRACT FROM AUTHOR]

It is well known that the waveguide beam splitter can be used as a source for the quantum entanglement of photons. The analysis of such quantum entanglement is a difficult problem even for monochromatic photons, since the system under study is multiparametric. This paper will show that quantum entanglement can be represented in a simple form not only for monochromatic photons but also for non-monochromatic ones. It will be shown that quantum entanglement for non-monochromatic photons can be very different from monochromatic photons, which can be used to create large quantum entanglement. [ABSTRACT FROM AUTHOR]

A light beam may be separated into its orbital-angular momentum (OAM) components by a geometric optical transformation that converts each OAM component into a plane wave with a transverse phase gradient. Subsequent focusing produces a spot the lateral position of which is proportional to the input OAM state (Lavery et al 2012 Opt. Express 20 3). In this paper, we improve this approach, extending the measurement bandwidth to >50 OAM states and showing a simultaneous measurement of the radial coordinate. [ABSTRACT FROM AUTHOR]

The possibility of forming a set of spatially dispersed and mutually orthogonal beams in an array antenna has been known long ago. The method for obtaining a device that forms a fan of beams for arrays with the number of elements and beams equal to N=2^p was suggested by Butler. Realizing a fan of mutually orthogonal beams for arrays with any N, was shown by us in “Synthesis of pattern forming networks” Radio Engineering and Electronic Physics, vol. 27, no. 7, pp. 28–35, 1982. The schemes of the corresponding devices for N=5, 6 and 8 were also represented, however, the method for building a concrete scheme was described there without details. The present paper is dedicated to the procedure of synthesizing a beam-forming device based on the factorization of its transmission matrix, at this point, each factor represents a matched and decoupling hybrid. As a result, the beam-forming network is represented by a cascade connection of elementary matrices containing one hybrid or several 90^\circ phase shifters. The procedure is illustrated using examples of synthesizing matrices for N=8 and N=9 having broadside beams, and also that for N=6 where the left and right beams are symmetrical as normally assumed for “Butler” matrices. Furthermore, the scheme with N=8 is compared with the corresponding “Butler” matrix. [ABSTRACT FROM AUTHOR]

Based on single-photon spin-orbit entanglement, we propose in this paper an experimental scheme to sort orbital angular momentum (OAM) by cascading conventional polarizing beam splitters. An economical algorithm, taking advantage of the pair's complementary notation of OAM numbers, is designed to separate a mixture of definite OAM. Our scheme provides an alternative technique to encode OAM onto multiple spin states based on a Huffman tree and its potential in optical communication is demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents a new concept of frequency coherence in the frequency-time domain to describe the field correlations between two lightwaves with different frequencies. The coherence properties of the modulated beams from lightwave sources with different spectral widths and the modes of Fabry-Pérot (FP) laser are investigated. It is shown that the lightwave and its corresponding sidebands produced by the optical intensity modulation are perfectly coherent. The measured linewidth of the beat signal is narrow and almost identical no matter how wide the spectral width of the beam is. The frequency spacing of the adjacent FP modes is beyond the operation frequency range of the measurement instruments. In our experiment, optical heterodyne technique is used to investigate the frequency coherence of the modes of FP laser by means of the frequency shift induced by the optical intensity modulation. Experiments show that the FP modes are partially coherent and the mode spacing is relatively fixed even when the wavelength changes with ambient temperature, bias current and other factors. Therefore, it is possible to generate stable and narrow-linewidth signals at frequencies corresponding to several mode intervals of the laser. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the error caused by the beamspace transform (BT) when it is applied to uniform circular array (UCA) configuration. Several algorithms for direction of arrival (DoA) estimation exploit this modal transform because it allows using computationally efficient techniques such as polynomial rooting and dealing with coherent sources. The BT is based on the phase-mode excitation principle. The performance of such DoA estimators is degraded if the array has a small number of elements. We introduce a modified beamspace transform (MBT) that performs mapping from element-space to beamspace domain taking into account the error caused by the transform. Justification of the difference in the statistical performances of MUSIC and root-MUSIC algorithms for UCA is also given. Moreover, we show that there is a significant difference in the performance of the UCA root-MUSIC technique depending on whether an even or odd number of elements is used. We derive an expression approximating the bias in the DoA estimates that is caused by the beamspace transform. Some design guidelines are provided for choosing the key UCA configuration parameters such as number of sensors, array radius, and interelement spacing in order to reduce the error. Finally, we propose a novel technique for bias removal. It allows practically bias-free DoA estimation. [ABSTRACT FROM AUTHOR]

Parabolic cylindrical reflectors (PCRs) can have a large field of view, for example a 15 m reflector can access an area of 1° by 120° at 1.4 GHz. It is seen that the radiation pattern is asymmetric. This causes problems in situations where the radiation pattern rotates with time, such as radio astronomy. The rotation of the radiation pattern limits the field of view. In this paper a normalized signal to noise ratio is calculated for a full observation and this is then used to determine the field of view. The greatest variation occurs where the radiation pattern of a single feed element is used. The variation is reduced by RF beam-forming. If the radiation pattern has an aspect ratio of 2.5:1 the observed field of view is approximately constant and has a value that is three times larger than that of an equivalent parabolic dish. [ABSTRACT FROM AUTHOR]

This paper studies thermocapillary vortices induced by local heating of a bubble surface in a Hele-Shaw cell by a light beam. It is found that the vortex rotation frequency and its depth depend on the distance from the light-beam projection onto the layer to the bubble boundary. The surface velocity of the thermocapillary flow is calculated using the balance of the near-surface and return flows of the thermocapillary vortex and the equality of capillary and dynamic pressures. It is shown that a decrease in the surface velocity and the vortex rotation frequency with increase in the distance from the light beam to the bubble surface is due to a decrease in the temperature gradient between the illuminated and cold poles of the bubble. [ABSTRACT FROM AUTHOR]

This paper reports a novel optoelectronic nonlinear oscillator, which produces a chaotically phase-modulated light beam over a bandwidth greater than 5 GHz. The setup is intended for high-speed chaos-based secure communications. The nonlinear process is performed by the transient response of a fiber interferometer. The flexibility in the definition of such an all-optical nonlinearity features a potentially high-dimensional key space of the encryption process. Modeling, simulations, and experimental results of the dynamical behaviors are reported. [ABSTRACT FROM AUTHOR]

Metasurface-based beam splitters attracted huge interest for their superior properties compared with conventional ones made of bulk materials. The previously reported designs adopted discrete metasurfaces with the limitation of a discontinuous phase profile. In this paper, we propose a dual-band beam splitter, based on an anisotropic quasi-continuous metasurface, by exploring the optical responses under x-polarized (with an electric field parallel to the direction of the phase gradient) and y-polarized incidences. The adopted metasurface consists of two identical trapezoidal silicon antenna arrays with opposite spatial variations that lead to opposite phase gradients. The operational window of the proposed beam splitter falls in the infrared and visible region, respectively, for x- and y-polarized light, resulting from the different mechanisms. When x-polarized light is incident, the conversion efficiency and total transmission of the beam splitter remains higher than 90% and 0.74 within the wavelength range from 969 nm to 1054 nm, respectively. In this condition, each array can act as a beam splitter of unequal power. For y-polarized incidence, the maximum conversion efficiency and transmission reach approximately 100% and 0.85, while the values remain higher than 90% and 0.65 in the wavelength range from 687 nm to 710 nm, respectively. In this case, each array can be viewed as an effective beam deflector. We anticipate that it can play a key role in future integrated optical devices. [ABSTRACT FROM AUTHOR]

The Sagnac effect is usually considered as being a relativistic effect produced in an interferometer when the device is rotating. General relativistic explanations are known and already widely explained in many papers. Such general relativistic approaches are founded on Einstein's equivalence principle (EEP), which states the equivalence between the gravitational "force" and the pseudo-force experienced by an observer in a non-inertial frame of reference, included a rotating observer. Typically, the authors consider the so-called Langevin-Landau-Lifschitz metric and the path of light is determined by null geodesics. This approach partially hides the physical meaning of the effect. It seems indeed that the light speed varies by c ± ω r in one or the other direction around the disk. In this paper, a slightly different general relativistic approach will be used. The different "gravitational field" acting on the beam splitter and on the two rays of light is analyzed. This different approach permits a better understanding of the physical meaning of the Sagnac effect. [ABSTRACT FROM AUTHOR]