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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 study of optical topological insulators (PTIs) has revealed intriguing optical properties that diversify the ways in which light can be manipulated, offering significant potential for a wide range of applications. This paper presents a machine learning (ML)-based approach for the reverse design of optical PTIs. Using finite element methods, the paper addresses the challenge of computing the band structure of a dual-band model, enabling the construction of a dataset suitable for ML training. With the goal of maximizing dual-band bandgaps, the study employs the random forest algorithm to predict target parameters and further designs topological edge states. Leveraging these boundary state patterns, two different optical PTI beam splitters are devised, and their transmission coefficients and losses are computed. The results demonstrate that optical devices designed using topological boundary states exhibit enhanced stability and robustness. This approach offers a reliable solution for applications in fields such as optical communication and optical sensing. [ABSTRACT FROM AUTHOR]

Metasurfaces have gained a considerable amount of interest in the past decade for their capabilities to manipulate electromagnetic (EM) waves in different manners. They have offered multiple functionalities in terms of wave control depending on the given application. In terms of wave control, particularly EM beam splitting, it can be challenging compared to the given literature review, to achieve a wide number of beam-splitting reflections and coverage for multiple incident angles simultaneously. In this paper, we focus on the design of a metasurface based on the methodology of high periodicity supercell design (5.76 λ) and impedance modulation to achieve a various number of beam-splitting angles, while maintaining the same coverage at multiple incident angles for millimeter-wave (mm-Wave) frequencies. Following the generalized phase law of reflection alongside proper optimization of the surface impedance, the proposed reflective anomalous beam splitter (RABS) metasurface is designed to be polarization independent, and high reflection efficiency is achieved with a wave beam split into 11 different directions while operating for multiple incident angles simultaneously, making it a promising candidate to overcome challenges for various mm-Wave communication applications, especially in expanding 5G coverage in non-line of sight regions at a 28 GHz frequency band. The performance of the RABS metasurface is evaluated using both full-wave simulations and experimental measurements, which demonstrate its effectiveness in achieving 11 efficient reflective anomalous beams with a reflection efficiency of up to 96.65% and 97.36% in TE and TM modes at 28 GHz. [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]

This paper presents a polarizing beam splitter (PBS) based on a hexagonal lattice silver-filled photonic crystal fiber (PCF) with two silver wires, which possesses advantages such as a short splitting length, high extinction ratio (ER), and an ultra-wide bandwidth in commonly used communication bands. Utilizing the full-vector finite element method (FV-FEM), thorough investigations were conducted on lasers within the wavelength range of 1.1 to 1.9 μm. The PBS demonstrates a working bandwidth of 725 nm (1.14 to 1.865 μm) under an ultra-short splitting length of 55.3 μm, with an ER exceeding 20 dB, covering all bands of O + E + S + C + L + U optical communication, and achieving a maximum ER of 74.65 dB, where the surface plasmon resonance (SPR) effect of silver metal plays a significant role. It not only features an ultra-short splitting length and an ultra-wide splitting bandwidth but also exhibits excellent manufacturing tolerances and anti-interference capabilities. This polarizing beam splitter represents a promising candidate in communication and may find various applications in optical communication. [ABSTRACT FROM AUTHOR]

This paper presents a novel pentagonal structure dual-core photonic crystal fiber polarizing beam splitter (PS-DC-PCF PBS) filled with a nematic liquid crystal (NLC) in the central hole. Unlike previous designs with symmetric arrangements, the upper and lower halves of the structure have different air hole arrangements. The upper half consists of air holes arranged in a regular quadrilateral pattern, while the lower half features a regular hexagonal arrangement of air holes. By filling the central hole with birefringent liquid crystal, the birefringence of the structure is enhanced, reducing the coupling lengths along the x polarization and y polarization directions. The polarization properties, coupling characteristics, and the influence of different structural parameters on the extinction ratio of the polarizing beam splitter are analyzed using the full-vector finite element method. Simulation results demonstrate that the designed PS-DC-PCF PBS achieves a maximum extinction ratio (ER) of 72.94 dB with a splitting length of only 61.9 μm and a wide operating bandwidth of 423 nm (1.324–1.747 μm), covering most of the O, E, S, C, L, and U communication bands. It exhibits not only ultra-short splitting lengths and ultra-wide splitting bandwidth but also good manufacturing tolerances and anti-interference capabilities. The designed PS-DC-PCF PBS could provide crucial device support for future all-optical communication systems and has potential applications in fiber optic communication or fiber laser systems. [ABSTRACT FROM AUTHOR]

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]

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]

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]

Polarization processors with versatile functionalities are needed in optical systems, which use or manipulate polarized light. In this paper, we propose and realize an integrated polarization processor based on a coherent 4-port micro-ring resonator. The arbitrary unknown polarization state is input to the polarization processor via a 2-dimensional grating coupler (2DGC), which serves as a polarization beam splitter. The coherent 4-port micro-ring resonator (MRR) operates as a unitary processor and is formed by one crossbar micro-ring resonator and two thermally tunable phase shifters, one of which tunes the micro-ring while the other tunes the coherent interference between the two inputs from the 2DGC. The 4-port system can be used to control the input polarization states that appear at the two output ports and, therefore, can be used to implement a multi-function polarization processor, including polarization descrambler, polarization switch, polarizers, and polarization analyzer (both division of space (DOS) and division of time (DOT)). In this paper, we experimentally demonstrate the use of coherent 4-port MRR for polarization mode switching and for polarization mode unscrambling. The polarization unscrambler was capable of separating two polarization-multiplexed 40 GHz data lanes from the input fiber with crosstalk levels below −21 dB and is suitable for use in the receiver for polarization-multiplexed direct-detection optical communications systems. The same photonic circuit may be used as a polarization analyzer, either as a DOS polarization analyzer or a DOT polarization analyzer. The DOS polarization analyzer measured the polarization with measured deviation of the orientation angle (2ψ) varying from −0.5° to 1.3°and deviation of ellipticity angle (2χ) varying from −0.98° to 7.27°. The DOT polarization analyzer measured the polarization with a deviation of the orientation angle (2ψ) that varied from −2.93° to 3.49° and deviation of ellipticity angle (2χ) that varied from −3.5° to 3.05°. [ABSTRACT FROM AUTHOR]

Progress on two-dimensional materials has shown that valleys, as energy extrema in a hexagonal first Brillouin zone, provide a new degree of freedom for information manipulation. Then, valley Hall topological insulators supporting such-polarized edge states on boundaries were set up accordingly. In this paper, a two-dimensional valley crystal composed of six tunable dielectric triangular pillars in each unit cell is proposed in the photonic sense of a deformed Su–Schrieffer–Heeger model. We reveal the vortex nature of valley states and establish the selection rules for valley-polarized states. Based on the valley topology, a rhombus-shaped beam splitter waveguide is designed to verify the valley-chirality selection rule above. Our numerical results entail that this topologically protected edge states still maintain robust transmission at sharp corners, thus providing a feasible idea for valley photonic devices in the THz regime. [ABSTRACT FROM AUTHOR]

In this paper, a novel microwave photonic filter (MPF) based on a single longitudinal mode Brillouin laser achieved by parity time (PT) symmetry mode selection is proposed, and its unparalleled ultra-narrow bandwidth as low as to sub-kHz together with simple and agile tuning performance is experimentally verified. The Brillouin fiber laser ring resonator is cascaded with a PT symmetric system to achieve this MPF. Wherein, the Brillouin laser resonator is excited by a 5 km single mode fiber to generate Brillouin gain, and the PT symmetric system is configured with Polarization Beam Splitter (PBS) and polarization controller (PC) to achieve PT symmetry. Thanks to the significant enhancement of the gain difference between the main mode and the edge mode when the polarization state PT symmetry system breaks, a single mode oscillating Brillouin laser is generated. Through the selective amplification of sideband modulated signals by ultra-narrow linewidth Brillouin single mode laser gain, the MPF with ultra-narrow single passband performance is obtained. By simply tuning the central wavelength of the stimulated Brillouin scattering (SBS) pumped laser to adjust the Brillouin oscillation frequency, the gain position of the Brillouin laser can be shifted, thereby achieving flexible tunability. The experimental results indicate that the MPF proposed in this paper achieves a single pass band narrow to 72 Hz and the side mode rejection ratio of more than 18 dB, with a center frequency tuning range of 0–20 GHz in the testing range of vector network analysis, which means that the MPF possesses ultra high spectral resolution and enormous potential application value in the domain of ultra fine microwave spectrum filtering such as radar imaging and electronic countermeasures. [ABSTRACT FROM AUTHOR]

The application of precision interferometers is generally restricted to expensive and smooth high-quality surfaces. Here, we offer a route to ultimate miniaturization of interferometers by integrating a beam splitter, reference mirror, and light collector into a single optical element, an interference lens (iLens), which produces stable high-contrast fringes from the in situ surface of paper, wood, plastic, rubber, unpolished metal, human skin, etc. A self-referencing real-time precision of a sub-20 picometer (∼λ/30 000) is demonstrated with simple intensity detection under ambient conditions. The principle of iLens interferometry has been exploited to build a variety of compact devices, such as a paper-based optical picobalance, having 1000 times higher sensitivity and speed, when compared with a high-end seven-digit electronic balance. Furthermore, we used cloth, paper, and polymer films to readily construct broadband acoustic sensors possessing matched or higher sensitivity when compared with piezo and electromagnetic sensors. Our work opens the path for affordable yet ultraprecise frugal photonic devices and universal microinterferometers for imaging. [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]

In this paper, the thermo-optical performance using novel cooling strategy improvements for a hybrid photovoltaic/parabolic dish concentrator with a conical thermal receiver using a beam splitter filter (PV/PDC-CTR-BSF) is investigated. The study's main goal is to improve the cooling effectiveness of the serpentine-shaped cooling duct by investigating the effect of the cross-section shape and positioning of the cooling duct under the PV panel. Typical cooling pipes have either a rectangular or circular cross-section and are usually attached to the back sheet of the PV panel using off-the-shelf adhesives that have very low thermal conductivity. With the advent of 3D printing technology, the back sheets could be 3D-printed with integral cooling ducts of different cross-sections at different locations and orientations within the back sheet that allow for increased heat transfer from the back sheet and thus improve PV/PDC-CTR-BSF's thermos-optical performance. For this purpose, the study investigates and compares the thermal performance of four different cooling duct cross-sections that include: rectangular, semi-circular, semi-elliptical and triangular. For each of the cooling duct cross-sections, several positions and orientations, which include flush below the back sheet layer and embedded inside the back sheet but positioned at the bottom, middle and top of the back sheet, are examined. Numerical simulations using the commercial software ANSYS FLUENT(R2019) are performed to assess the performance of the cooling ducts and, in turn, the thermo-optical performance of the PV/PDC-CTR-BSF system. The semi-elliptical cross-section duct embedded in the middle of the back sheet was found to yield the best cooling performance since its rate of heat removal from the PV back sheet was found to be the highest. [ABSTRACT FROM AUTHOR]

Aerial displays for providing road information require long-distance image formation and a compact installation space. This paper proposes a compact optical system for forming long-distance floating images by introducing a Fresnel lens in an aerial imaging by retro-reflection (AIRR) optical system. In the conventional AIRR optics, since the aerial image position is the plane-symmetrical position of the light source with respect to the beam splitter, the installation space for forming a long-distance aerial image becomes huge. Our proposed method uses the virtual image formed by a Fresnel lens as the light source in an AIRR optical system. This leads to a much longer distance from the beam splitter to the aerial image than the distance from the beam splitter to the light source. We developed a prototype long-distance floating aerial display system using a large-scale Fresnel lens. As a result, the distance from the LED panel to the beam splitter was halved. Furthermore, we used two beam splitters to form two aerial images by using a single LED panel. Long-distance floating images could be formed 3.4 m and 4.6 m away from the beam splitters and could be seen with the naked eye. [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, we investigate a system composed of two spatially separated cavities, each with a magnon mode of a yttrium iron garnet (YIG) sphere coupled to a microwave (MW) cavity and phonon modes, respectively, via linear beam splitter and magnetostrictive interactions. In addition, two-mode squeezed vacuum fields drive the two cavities. We investigate and compare the behavior of three nonclassicality indicators in two subsystems (i.e., magnon–magnon and phonon–phonon) under the influences of the temperature, the cavity–magnon damping rate, and the magnomechanical coupling rate. We use the entanglement of formation (EoF) to measure the degree of entanglement, the Gaussian quantum discord (GQD) to characterize the quantum correlations beyond entanglement and Gaussian quantum coherence (GQC) to quantify coherence. Considering that the quantifiers share the same entropic definition, we compare the three quantifiers and test the validity of the hypothesis that quantum states with nonzero discord are inherently entangled. We find, on the one hand, that both GQC and GQD exhibit freezing behavior and that they are more robust to the decoherence effect than the EoF. On the other hand, the EoF and the GQD are always upper bounded by GQC, and there is no simple dominance relationship between EoF and GQD; hence these two quantifiers should not be compared. The effect of other parameters is also discussed in detail. [ABSTRACT FROM AUTHOR]

With zeroth-order suppression, a double-groove reflective grating for dual-port reflection beam splitter is studied in this paper. Under normal incidence, the grating obtains great efficiencies for both TE and TM polarizations. The parameters of the double-groove grating are derived using rigorous coupled-wave analysis. The finite element method and the simulated annealing algorithm are also presented to make sure that the ideal parameters are obtained. Total efficiencies of 98.95% for TE polarization and 99.30% for TM polarization are realized at an incidence wavelength of 1550 nm. In the meantime, the efficiencies of TE polarization and TM polarization at ± 1st orders are 48.15% and 46.26%, while at zeroth order, they are being effectively suppressed at 2.41% and 6.56%. The suggested grating has exceptional qualities and performs admirably. [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]

In the paper the methods of laser hardening of external tool corners on the example of bending tools for press brakes were presented. The disadvantages and limitations of the most commonly used techniques for guiding a hardening laser light beam are presented, i.e.: (i) in one pass parallel to the tool corner plane symmetry, (ii) in two passes perpendicular to the surfaces adjacent to the corner, and (iii) in one pass perpendicular to the surface adjacent to the corner by using two diode lasers. The microstructure of the tool material after laser and induction hardening was compared. A significant influence of the heating method on the microstructure of the tool material after hardening was demonstrated. The original method of hardening the outer corners of bending tools using a hardening laser beam splitter was subject to a more detailed analysis. The analysis of material heating in simultaneously hardened corner area and adjacent surfaces was carried out using the Marc/Mentat software based on the finite element method. By analyzing the temperature distributions it was shown that if a beam splitter was used, obtaining a continuous and uniform hardened layer (i.e. with comparable hardness, depth, without tempered or non-tempered areas) in the area of the outer corner and adjacent surfaces was possible. In practice, achieving such a layer is conditioned by the correct selection of the size of the k parameter which determines the distance between the separated beams of laser light. Depending on the geometry of the hardened tool corner and the parameters of the hardening laser beam, this distance can be determined experimentally or on the basis of numerical simulation. [ABSTRACT FROM AUTHOR]

In this paper a procedure to design transmissive metasurfaces based on graphene-metal hybrid layers is developed and employed to design a multi-functional reconfigurable structure. Due to the inclusion of graphene, with tunable conductivity, different applications are achieved without any physical changes in the structure and by just varying the chemical potential of graphene through an electrostatic bias voltage. The designed structure consists of four identical layers to provide 360° phase-shift range with acceptable amplitude and full control of the transmitted wave front. By imposing an appropriate phase gradient profile on the supercell, several applications like beam steering, lens with arbitrary focal length and beam splitter with arbitrary angles are achieved. Simulation results of near field distributions as well as far field patterns vindicate the effectiveness of the proposed design procedure. The designed structure is promising for applications in the 6G wireless communication networks, nano-photonic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

In the context of variational compiling of a continuous-variable (CV) unitary operation, the architecture and parameter space of the Xanadu X8 processor constrain both the set of feasible compiling problems and the allowed cost functions. In this paper, we motivate a faithful cost function for variational compiling of a two-mode, continuous-variable beam splitter gate with real matrix elements (i.e., a "zero-phase" beam splitter) that complies with the constraints of the X8 processor. This cost function is then computed on the X8. Despite the noise in the processor, we find that the cost function exhibits optimum parameter resilience and, therefore, that this variational compiling problem is feasible on the X8. The intent of the paper is partly to report a proof-of-principle cost function calculation on near-term CV hardware and partly to present methods that may be relevant for CV variational compiling problems in more complicated, large scale settings. [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]

While the quantum metrological advantages of performing non‐Gaussian operations on two‐mode squeezed vacuum (TMSV) states have been extensively explored, similar studies in the context of two‐mode squeezed thermal (TMST) states are severely lacking. This paper explores the potential advantages of performing non‐Gaussian operations on TMST state for phase estimation using parity detection‐based Mach–Zehnder interferometry and compares it with the TMSV case. To this end, a realistic photon subtraction, addition, and catalysis model is considered. A unified Wigner function of the photon subtracted, photon added, and photon catalyzed TMST state is derived, which is used to obtain the expression for the phase sensitivity. The results show that performing non‐Gaussian operations on TMST states can enhance the phase sensitivity for significant squeezing and transmissivity parameter ranges. Because of the probabilistic nature of these operations, it is of utmost importance to consider their success probability. When the success probability is considered, the photon catalysis operation performed using a high transmissivity beam splitter is the optimal non‐Gaussian operation. This contrasts with the TMSV case, where photon addition is observed as the most optimal. Further, the derived Wigner function of the non‐Gaussian TMST states will be useful for state characterization and various quantum protocols. [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]

The phase retrieval method based on the Transport of Intensity Equation needs to record the light intensity information on two or more planes perpendicular to the optical axis propagating along the optical axis. Usually, a single CCD camera is moved back and forth for recording, which not only brings the corresponding mechanical errors, but also has a certain time difference between the collected intensity images, which cannot meet the real-time requirements. In this paper, a single phase retrieval technique based on cube-corner prisms is proposed. This method can simultaneously collect the required initial intensity image in a single exposure, and then calculate the phase after registration and repair, so as to obtain high-precision results. According to the parallel reflection characteristics of the cube-corner prisms, the experimental system designed correspondingly can not only stagger the two beams separated by the beam splitter, but also ensure that the upper and lower propagation distances of a single beam are equal. Finally, the accuracy and effectiveness of the proposed method are fully verified by simulation experiments and experimental measurements. [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]

In this paper, we investigate the optical analog to coherent population return (CPR) in coupled nonlinear waveguides. The nonlinearity sometimes plays a negative role in classical simulations of quantum adiabatic passages in waveguides. Nevertheless, it is interesting to note that the nonlinearity here helps simulating the adiabatic CPR technique. The CPR can still occur when the detuning (difference of the propagation constants) between the two nonlinear waveguides is moderate, which is a typical requirement of the technique. Moreover, the adiabatic process can appear when the detuning is small or zero. This is done by simply adjusting the incident light power, which is easy and of high accuracy compared with modulating the propagation constants. Therefore, the requirements towards the propagation constants of the waveguides are further relaxed in the nonlinear case. Finally, we point out that the CPR in nonlinear waveguides can be extended to design achromatic beam splitters. [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]

Design of the optical devices is an important matter of discussion in the present scenario where optical devices have become ultra‐compact due to miniaturization, ultra‐speed with the integration of optoelectronic devices. In this paper a 1 × 3 2D photonic crystal based on optical beam‐splitter has been designed on OptiFDTD for TE polarized light. The wafer is of the dimensions of 21 µm × 15 µm in length and width, respectively. The design works at the wavelength of 1.55 µm, and the mode is selected to be the Gaussian Modulated Continuous Wave (GMCW). The design is based on the 2D Hexagonal lattice, where the elliptical Si‐rods are placed in the air. This splitter prototype consists of one input and three outputs with the split ratio as 60:20:20. This refers to the first output port has 60% power of the transmitted signal, and the second and the third output ports have 20% power of the input. The structure is implemented using OptiFDTD software. It utilizes Finite Domain Time Difference (FDTD) numerical method to analyze the transmission spectra of the structure, and the Plane Wave Expansion (PWE) method is utilized to calculate the photonic bandgap of the prototype. [ABSTRACT FROM AUTHOR]

We propose multiple aerial imaging system by use of two beam splitters in the optical system of aerial imaging by retro-reflection (AIRR). The AIRR optical system consists of a light source, a beam splitter, and a retro-reflector. Use of two-layered beam splitters enables us to show multiple aerial signs to drivers in multiple driving lanes. The purpose of this paper is to confirm feasibility that an aerial display by use of AIRR for a novel traffic information provision. First, we explain an optical configuration to show aerial images to multiple road lanes, a driving lane and an overtaking lane with AIRR by use of two beam splitters. Next, we have developed a prototype optical system by use of two large beam splitters and a large high-brightness LED sign that is designed to be used for actual road displays. The light source was an LED display with a height of 450 mm and a width of 390 mm, which shows a character. We observed aerial images by naked eyes as experiments. And we discuss the issues for practical application that the experiments have revealed. [ABSTRACT FROM AUTHOR]

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In this paper, we theoretically study the concept of the wave–particle duality of two entangled neutral Bragg diffracted atoms. This is an extension of a recent study where the same idea was proposed in the photonic setup [Man et al., Sci. Rep. 7, 42539 (2017)] using two independent Mach–Zehnder interferometers. Now, we propose a similar scheme using the cavity-QED based setup, which comprises two independent atomic de Broglie Mach–Zehnder–Bragg interferometers, a source cavity that generates two external momenta state entangled atoms. Once the atoms pass through the source cavity initially prepared in the superposition of zero and one photon, they emerge out of the cavity in entangled momenta state such that if one atom is transmitted to the upper interferometer, then the second atom must traverse the lower interferometer, and vice versa. The final atomic de Broglie beam splitter at the top interferometer is prepared in the superposition of zero and one photon and facilitates observing the wave or particle aspect in a single setting. This entire setup functions in off-resonant Bragg diffraction and the proposed schematics are shown to be experimentally feasible under contemporary research scenarios. [ABSTRACT FROM AUTHOR]

Determining if a quantum state is separable or entangled is a complex problem. Proposed schemes usually employ the von Neumann entropy, the positivity of the partial transpose or various inequalities. Determining the separability of the output of an optical system is an even more involved task. In this paper, we find necessary conditions for the output separability of a SU(2) system. We first discuss some previously reported criteria, showing their limitations. We then introduce our covariance-based criterion and assess its performance. For a system having one input port in the vacuum state, we arrive at a very simple criterion for the output separability. For pure input states, we introduce an artifice to easily assess the output separability with the help of the two-parameter quantum Fisher information. Applications of the proposed criterion are given by evaluating the output separability of a non-balanced beam splitter, fed by a number of input states. [ABSTRACT FROM AUTHOR]

The paper presents an optical method based on auto-collimation to simultaneously measure five degrees of freedom error motions of the rotary axis. The proposed method consists of the collimated lasers, beam splitters, focusing lens, quadrant photodiode detectors, a high-precision steel ball, and a special mirror fixed to the rotary axis. The mathematical model is established byoptical ray tracing, and the corresponding optical path is also simulated by OpticStudio. Meanwhile, an adjusting mechanism for X–Y micro-displacement, based on the elastic deformation of the material, is designed to adjust the installation eccentricity error of the high-precision steel ball. The calibration results of the proposed system demonstrate that the displacement errors are ±0.25 µm within the measuring range of ±10 µm, and the tilt angle errors are ±0.6 arcsec within the measuring range of ±25 arcsec. Taking a direct drive (DD) motor as the test object, the radial error motions of the rotary axis range from −3.2 to 4.1 µm, the axial error motions range from −4.9 to 4.7 µm, and the tilt error motions around the X and Y axes range from −2.8 to 1.8 arcsec and −2.6 to 2.0 arcsec, respectively. [ABSTRACT FROM AUTHOR]

Purpose: Multiple-source disturbances exist in the polarization sensor, which severely affect the sensor accuracy and stability. Hence, the disturbance analysis plays a vital role in improving the sensor orientation performance. This paper aims to present a novel sensor error model, a disturbances quantitative analysis, a calibration and performance test of polarization sensor based on a polarizing beam splitter. Design/methodology/approach: By combining with the sensor coefficient errors, the Azimuth of Polarization (AoP) error model and the Degree of Polarization (DoP) error model are established, respectively. In addition, the multiple-source disturbances are classified, while the influence on the orientation accuracy is quantitative analyzed. Moreover, the least square optimization algorithm is employed to calibrate the sensor coefficients. Finally, an outdoor test is carried out to test the sensor long-term accuracy. Findings: The theoretical analysis and numerical simulations illustrate that the sensor accuracy is closely related to the disturbances. To eliminate the influence of the disturbances, the least square optimization algorithm, which can minimize the sum of squares of the residual difference of AoP and DoP, is used to calibrate the sensor coefficients. The outdoor test indicates that the sensor can maintain long-term accuracy and stability. Originality/value: The main contribution of this paper is to establish a novel sensor error model, where the sensor coefficient errors are introduced. In addition, the disturbances are classified and analyzed to evaluate the orientation accuracy of the sensor. [ABSTRACT FROM AUTHOR]

In this paper, unlike many researches that focus on beam splitters based on gratings with symmetrical structures, an asymmetric grating with double-groove structure is proposed. Based on the double-groove grating, multi-port beam splitters including dual-port, three-port, and four-port, under normal incidence working at terahertz frequency are designed for both transverse-electric and transverse-magnetic polarizations. Rigorous couple-wave analysis and simulated annealing algorithm are employed to get the optimal parameters of the grating and accelerate the computing process. For the purpose of understanding the phenomenon of the beam incident, the finite element method is also applied to get the simulation result. It is proven that the proposed beam splitters all present great efficiency and uniformity on the energy distribution. High manufacturing tolerance of the beam splitters is also analyzed, which allows for greater flexibility in the fabrication process. Compared with beam splitters based on single-groove grating, multi-port beam splitters based on double grooves show great performance and universality. [ABSTRACT FROM AUTHOR]

To improve the accuracy of infrared radiation characteristics measurement in the aviation field, an infrared Fourier transform imaging spectrometer based on a double-swing solid angle reflector was designed. This imaging spectrometer operates in the 3–5 μm wavelength range and has a field of view of 1.7° × 1.7°. This article presents a comprehensive analysis of the system's stray light and also studies the impact of external stray light on the imaging quality, along with the influence of internal stray light on the interference effects and the spectral resolution. It also present the design of a hood that suppresses the point source transmittance of the external stray light down to the order of 10−4. Based on this, we propose a method that incorporates the introduction of wedge and inclination angles. Additionally, a numerical range is provided for the addition of these angles on the beam splitter mirror and compensation plate. This ensures the effective suppression of any internal stray light. This study fills the gap in the knowledge about Fourier transform imaging spectrometers operating in the mid-infrared band for aviation applications, and proposes a suppression method suitable for interference systems, which is also suitable for Fourier transform imaging spectrometers based on other types of interferometers. This study broadens the application field of Fourier transform imaging spectrometers in stray light, and has great significance to promote the development of Fourier transform imaging spectrometer. [ABSTRACT FROM AUTHOR]

Many devices based on silicon and other photonic integrated circuit platforms exhibit significant polarization dependence. Polarization beam splitter (PBS) is a device that split optical signals into transverse electric (TE) and transverse magnetic (TM) modes. Among various PBSs, asymmetric directional couplers are widely used due to their fine performance, but their working bandwidth is limited due to wavelength changes that can lead to deviations in effective refractive index and coupling strength. We propose a PBS, which uses metamaterial anisotropy to replace structural asymmetry and break the bandwidth bottleneck. It achieves good performance in the wavelength range of 258 nm, where the extinction ratio of the TM polarization is greater than 24 dB and that of the TE polarization is greater than 26 dB. It covers the E, S, C, L, and U bands, and the coupling area is as small as 7.25×2.625 μm, with a total device footprint of 15.65×6.125 μm. [ABSTRACT FROM AUTHOR]

In this paper, a triple-layer grating beam splitter with three-port output is designed. Through the combination of rigorous coupled-wave analysis (RCWA) and simulated annealing algorithms (SAA), the calculation and optimization of each parameter of the grating is carried out to make the diffraction efficiency of the grating meet the conditions. At the incident wavelength of 800 nm, the diffraction efficiencies of 0th order and ±1st order under TE polarization are 31.6% and 31.4%, respectively. The diffraction efficiencies of 0th order and ±1st order under TM polarization are 32.7% and 32.5%, respectively. It can be seen that not only the total diffraction efficiency under TE polarization and TM polarization exceeds 90%, but also the uniformity of diffraction efficiency at each order exceeds 99%. Finally, the influence of grating parameters and incident wave characteristics on diffraction efficiency is discussed. [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]