Optical Modes Research Articles

Quantum Repeater Protocol for Deterministic Distribution of Macroscopic Entanglement

AbstractDistributing long‐distance entanglement is a fundamental goal that is necessary for a variety of tasks such as quantum communication, distributed quantum computing, and quantum metrology. Currently quantum repeater schemes typically aim to distribute one ebit at a time, the equivalent of one Bell pair's worth of entanglement. Here, a scheme is presented to distribute a macroscopic amount of entanglement across long‐distances using a number of operations that scales only linearly with the chain length in the ideal case (without decoherence). The scheme involves ensembles of qubits and entangling them with an interaction, which can be realized using atomic gas ensembles coupled by a shared optical mode. Using only local measurements on the intermediate ensembles, this leaves the ensembles at the ends of the chain entangled. It is showed that there are particular “magic” interaction times that allow for distribution of entanglement with perfect fidelity, with no degradation with chain length. The scheme is deterministic, such that with suitable local conditional unitary corrections, the same entangled state can always be prepared with good approximation.

Amplify high harmonic generation via anharmonic phonons in PbTe

High-harmonic generation (HHG) provides insights into the nonlinear optics dynamics of the electrons with inherent attosecond temporal resolution. However, current strategies of HHG control suffer from low efficiency and weak radiation. Here we employ phonons in the field of high-harmonic generation over a broad range of wavelengths and elliptically polarized light, providing a significant approach for the efficient and flexible manipulation of HHG. Our results indicate that the symmetry breaking induced by transverse optical (TO) and transverse acoustic (TA) phonon modes can extremely enhance the intensity of HHG in PbTe. In addition, we report the emergence of magnetization due to the noncentrosymmetric states of the TO and longitudinal optical (LO) phonons. These results pave the way toward perturbative and nonperturbative nonlinear optics and significantly contribute to the attosecond science.

Torque Loss, Survival, and Strain Distribution of Implant-Supported Prostheses with Zirconia and Cobalt–Chromium Hybrid Abutments

Background and Objectives: The manufacturing of single crowns using hybrid abutments is an alternative that may be interesting in clinical practice, combining the advantages of the different materials used in a personalized design for each case. The purpose of this in vitro study was to evaluate the torque loss, survival, reliability, failure mode, and strain distribution of implant-supported prostheses with zirconia (Zir) and cobalt–chromium (Co-Cr) hybrid abutments. Materials and Methods: Abutments were milled by CAD/CAM and divided into two groups according to the materials used, Zir and Co-Cr, and cemented on titanium bases screwed to dental implants. Monolithic zirconia crowns were cemented on the abutments. The implant/abutment/crown sets were subjected to thermomechanical cycling (n = 10) (2 Hz, 140 N, 1 × 106 cycles, immersed in water at 5–55 °C) to evaluate the torque loss. The single load to fracture test (SLF) was performed to design the loading profiles (light, moderate, and aggressive) of the step-stress accelerated life testing (SSALT) (n = 21) to evaluate the survival and reliability. The representative fractured specimens were analyzed under optical and scanning electron microscopy. The digital image correlation (DIC) (n = 1) was performed using specimens embedded in polyurethane resin models that received static point loading, and the strain distribution was analyzed. Results: There was no difference in torque loss, survival, or reliability between zirconia and Co-Cr abutments. An analysis of the fractured surfaces showed that the abutments presented the same failure mode, where the fracture probably started in the titanium base/screw. The zirconia abutment model presented only compressive strains around the implant, while the Co-Cr abutment model showed tensile and compressive strains in the middle of the implant; however, all strains were within the clinically acceptable limits. There was a strain concentration in the titanium base close to the implant platform for both groups. Conclusions: Zirconia and Co-Cr hybrid abutments presented similar torque loss, survival, reliability, and failure modes, but the abutment material influenced the strain distribution around the implant. The titanium base screw was the weakest link in the system.

Purity and composite petal-Like mode laser emission with tunable topological charge from 1 to 35

Purity and composite petal-Like mode laser emission with tunable topological charge from 1 to 35

Перспективы развития волоконно-оптических систем измерений

Статья посвящена исследованиям в области распределенных и точечных волоконно-оптических измерений (РВОИ и ТВОИ). Представлены результаты этих исследований. Показаны направления разрешения проблем, связанных с одновременным использованием различных возможностей волоконно-оптической техники (ВОТ) для поиска наиболее продуктивных методов и технологий комплексирования антагонистических функций передачи диагностической информации на основе волоконно-оптических линий связи. The article is devoted to research and obtained results related to the field of distributed and point-based fiber-optic measurements based on coherent reflectometry. The necessity of overcoming the following main obstacle is shown: the high sensitivity of the fiber-optic cable laid along the railway track and used as the basis for building a distributed fiber-optic sensor for monitoring train movement parameters to vibroacoustic and seismoacoustic influences exerted during the interaction of wheelsets and rails during the passage of the train, which is the basis for improving the accuracy of optical measurements of train movement parameters, it also becomes an obstacle when transmitting ordinary information packets over other optical fibers of the cable in the mode of transmitting information over an optical communication line. Because of this, various requirements for laying an optical cable also appear: in the first case, as close as possible to the source of vibroacoustic and seismoacoustic effects to increase the sensitivity of distributed fiber-optic sensors, in the second – as far as possible to reduce interference when transmitting information in the optical communication line mode. To solve the existing problems, a method is proposed based on connecting optical coils assembled from optical fiber loops to certain optical fibers of the main optical cable at specified locations. At the same time, to ensure that the results of optical measurements on a distributed sensor are linked to a digital train movement map, the placement of coils is chosen combined with elements of the railway infrastructure that have an accurate geodetic reference. A distinctive feature of the innovations proposed in the article is the possibility of their joint use, which ensures a significant increase in the efficiency of optical measurements.

Crystal structure manipulation to achieve better thermoelectric performance in Te-substituted GeSe

GeSe has recently gained attention for its structural similarity to SnSe, an excellent thermoelectric material. However, for the orthorhombic GeSe, the maximum zT is limited to ∼0.2 at 700 K. A significant improvement in the thermoelectric performance is observed when GeSe is stabilized in a rhombohedral or cubic structure; thus, the crystal structure plays an important role in GeSe for improved zT. In this study, we investigated the structural transitions and thermoelectric properties of Te-substituted GeSe. Increasing Te substitution in GeSe1-xTex (x = 0.00–0.50) induces a transition from orthorhombic to rhombohedral crystal structure at ambient conditions with the maximum zT ∼ 0.58 observed in rhombohedral GeSe0.6Te0.4 at 573 K. The improved thermoelectric performance in the rhombohedral phase is due to a concurrent increase in the power factor and a decrease in lattice thermal conductivity. The phonon dispersion calculation tells that the high-frequency optical phonon modes significantly increase the phonon–phonon scattering for the rhombohedral phase, enhancing the lattice anharmonicity and reducing the lattice thermal conductivity. This behavior aligns with the presence of metavalent bonding in rhombohedral GeSe. Additionally, peak broadening observed in the Raman spectra of the rhombohedral phase indicates pronounced lattice anharmonicity and phonon modes softening due to the metavalent bond character.

Effect of Core Geometry on Frequency Correlations and Channel Capacity of a Multimode Optical Fiber

Photons are the fundamental carriers of classical and quantum information across long distances via optical fibers. Multimode fibers with many transverse optical modes can support high‐capacity communication through space‐division multiplexing. While spatial correlations in light transmission via fibers have been investigated for counteracting mode mixing, less is known about frequency correlations, which are critical for high‐capacity communication using ultrashort pulses. This study uses complex wavefront shaping methods to investigate how core geometry affects the frequency correlation bandwidth of structured wavefronts in circular and rectilinear‐core fibers. Measurements reveal that rectilinear‐core fibers exhibit up to a 40% increase in frequency correlation bandwidth compared to circular core fibers, particularly when focusing light away from the fiber center—common in spatially multiplexed optical communication. This enhanced bandwidth results in a 20% boost in optical communication channel capacity, highlighting the potential of rectilinear core fibers. Furthermore, this observation of novel spatiotemporal wave correlations could be exploited for application of rectilinear core fibers in chip‐to‐chip interconnects for photonic quantum processors, contributing to scale up of photonic quantum technologies.

Logic-qubit CNOT gates in decoherence-free subspaces assisted by the nitrogen-vacancy center.

Employing an optical microcavity interacting with a nitrogen-vacancy (NV) center with excellent optical performance and scalability, two logic-qubit controlled-not (CNOT) gates in decoherence-free subspaces (DFSs) are successfully constructed against collective-rotating noise and collective-dephasing noise, respectively. The circuit has a heralded function that can filter out incorrect components. Furthermore, a waveform corrector (WFC) is adopted to balance the amplitude of two components in different spatial modes, thereby achieving high fidelity.

Optimizing microstructure and minimizing defects in laser-arc hybrid additive manufacturing of Al-Cu alloy: the role of laser mode

Recently, laser-arc hybrid additive manufacturing (LAHAM) has emerged as a transformative method for producing lightweight aluminum alloys, valued for its advantageous surface quality and mechanical properties. In this study, the effect of various laser modes on macro morphology, defect formation, microstructure evolution, and mechanical properties of Al-Cu alloy were investigated. At a laser power threshold of 1.5 kW, the transition from conduction mode to keyhole mode was observed. When the keyhole formed, the molten metal exhibited enhanced fluidity, resulting in smoother surfaces and more uniform spreading. As laser power increased, although hydrogen-induced pores (HIP) were notably reduced, the keyhole-induced pores (KIP) began to appear. During subsequent depositions, the intense reheating effects from laser facilitated a transformation from reticular eutectics (RE) along grain boundaries to granular eutectics (GE). Additionally, recrystallization and formation of Σ3 coincidence site lattice (CSL) boundaries were restricted due to the reduced residual stress caused by moderating cooling rates, alleviating stress concentration near pores during deformation. Therefore, optimal results were achieved in conduction mode at a laser power of 1 kW, achieving highest tensile strengths of 269.5 MPa and 260.1 MPa, and elongations of 19.6% and 13.8% in horizontal and vertical directions, respectively.

Demonstration of a scalable mode converter in lithium niobate on insulator.

Lithium niobate on insulator (LNOI) attracts extensive attention from academic and industrial communities due to LN's excellent electro-optic (EO) properties, which also brings bright prospects for achieving high-speed and large-capacity photonic integrated circuits (PICs) including active and passive components such as modulator, filter, and multiplexer. A mode converter can implement optical mode conversion from a fundamental mode to a high-order mode, which plays a key role in an on-chip mode-division multiplexing (MDM) system. In this Letter, we propose high-performance and scalable mode converters in LNOI, and based on our proposed scalable principle, the mode converter can be designed to implement the optical mode conversion from the fundamental mode to arbitrary high-order mode. As a proof of concept, we design and fabricate TE0-TEi (i = 1,2,3) mode converters. The experimental results show the insertion loss (IL) and cross talk (CT) are less than 2.5 dB and -10.3 dB in the wavelength range of 1525-1565 nm for all fabricated devices, which are basically consistent with the simulation results. This work brings great promise for achieving high-performance PICs on the LNOI platform in the future.

Are mechanical and electromechanical methods accurately interchangeable for measuring plasma prothrombin time and activated partial thromboplastin time? A comparative analysis study and potential implication to cardiovascular disease

INTRODUCTION: The DT100 offers both optical and mechanical modes, with its mechanical mode showing better homogenization than the STAGO, but comparative study is limited. OBJECTIVES: The study aimed to evaluate the diagnostic accuracy of plasma Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT) measurements using the DT100 and STAGO instruments. METHODS: Designated as a cross-sectional study, this study was conducted at RSUD Dr. Soetomo from October 2022 to January 2023. Venous blood samples with plasma citrate anticoagulant 0.109 M 3.2% were consecutively collected from hospitalized patients, and all samples underwent testing using both the DT100 in mechanical mode (DT100, TCoag Ireland Limited, Ireland) and the STAGO employing an electromechanical method (Compact Max3, STAGO, France). Statistical analysis included comparison using Paired t-test, Pearson correlation, and Bland-Altman analysis to assess agreement between the results obtained from the two instruments. RESULTS: The study included 51 patients. PT levels were significantly lower with the DT100 compared to STAGO (MD: -2.0; 95%CI: (-2.30) – (-1.3); p<0.0001), and showed a strong positive correlation between methods (r:0.9535; p<0.0001). However, Bland-Altman analysis for PT showed a bias of 1.84, with limits of agreement (3.30-0.37), indicating systematic differences and variability. APTT levels were significantly higher with DT100 compared to STAGO (MD:3.60; 95%CI: 2.13–5.07; p<0.0001), with a moderate positive correlation (r:0.6690; p<0.0001). For APTT, bias of Bland-Altman analysis was -3.60, with limits ((-9.84) – (2.64)), suggesting significant discrepancies and variability between methods. CONCLUSION: The study found significant variability in PT and APTT measurements between the DT100 and STAGO methods. Keywords: Prothrombin time, activated partial thromboplastin time, mechanical method, DT100 TCoag, STAGO Compact Max 3

Dispersive heterodyne cavity ring-down spectroscopy exploiting eigenmode frequencies for high-fidelity measurements.

Measuring low light absorption with combined uncertainty <1 per mil (‰) is crucial for many applications. Popular cavity ring-down spectroscopy can provide ultrahigh precision, below 0.01‰, but its accuracy is often worse than 5‰ due to inaccuracies in light intensity measurements. To eliminate this problem, we exploit optical frequency information carried by the ring-down cavity electromagnetic field. Instead of measuring only the decaying light intensity, we perform heterodyne detection of ring-downs followed by Fourier analysis to provide exact frequencies of optical cavity modes and a high-fidelity dispersive spectrum of a gas sample from them. We demonstrate the sub-per-mil accuracy of our method, confirmed by the best ab initio results for CO line intensity and for HD line shape, and the long-term repeatability of our dispersion measurements at 10-4 level. We see potential for our approach in atmospheric remote sensing, isotope ratio metrology, thermometry, and establishment of primary gas standards.

Efficient frequency conversion via a wide-spanning intermodal four-wave mixing Bragg scattering process

We demonstrate efficient Bragg-scattering four-wave mixing frequency conversion in a few-mode fiber with two pumps spectrally separated from the signal and idler by 600 nm. The wideband frequency conversion is made possible by propagating the frequency components in two different spatial modes, the pumps are excited in the LP11 mode, while the signal is excited in the LP01 mode, and the Bragg scattering (BS) idler is generated in the LP01 mode. For these processes, we experimentally characterize their conversion efficiency and bandwidth. The dependency of conversion efficiency on peak pump power and the separation between BS components are measured, demonstrating a peak conversion efficiency of up to 79%.

High power, high beam quality and narrow linewidth diode-end-pumped Nd:YAG seed laser at 1319 nm for a sodium guide star laser system

Abstract A high power, high beam quality and narrow linewidth Nd:YAG 1319 nm pulsed seed laser for sodium beacon is demonstrated, which was dual-end-pumped by the low quantum loss 885 nm quasi-continuous wave laser diodes (LDs). The resonator was based on a ring convex–convex structure with a dual-rod configuration. Adjusting the effective pump size in the crystal and the temperature of the LDs to realize the optimal size ratio of the pump beam and laser mode was analyzed finely. An output power of up to 25 W at 1319 nm has been obtained, operating at 800 Hz with a pulse duration of 140 μs, corresponding to a high optical-to-optical conversion efficiency of 18%. The average beam quality factor of M 2 was measured to be 1.25. To the best of our knowledge, this is both the highest output power and the highest beam quality at 1319 nm for the 885 nm LDs end-pumped with the pulse oscillator. This result provides a 1319 nm seed laser for a sodium guide star laser system, with high quality (high power, high beam quality and narrow linewidth), and also better stability.

Improving the accuracy of vortex beam rotational velocity measurement based on phase recovery and polarization reference

In remote rotational velocity measurements, atmospheric turbulence-induced phase distortion of the vortex beam increases velocity measurement error (VME). Previous studies overlooked the reference to new dimensional information for measurement error analysis and accuracy enhancement. Our work proposes the Optimal Joint Reference VME (OJR-σ) method as a, to our knowledge, novel error optimization method; it references the measurement error information from the left- and right-handed polarized components (LP and RP) of the polarized vortex beam and optimizes the velocity measurements values weights of LP and RP in the result to minimize the VME. Combined with the GS phase recovery algorithm, this method effectively reduces system VME, enabling distortion compensation and optimal VME mode distribution evaluation. The results indicate that the OJR-σ method achieves a lower VME advantage across all modes compared to both the General Joint Reference VME (GJR-σ) and General VME (G-σ) methods, with maximum VME decreases of 29% and 71% for the High VME decline rate modes, respectively. Additionally, the OJR-σ method exhibits fewer High VME modes, resulting in an average VME of 83.6% and 71.0% compared to the other two methods. After GS compensation, the VME of High VME modes decreases by 6.12%, 4.7%, and 6.78% for the three error methods, respectively. Furthermore, the OJR-σ method proves more effective than GJR-σ in reducing the VME for high topological charge modes, achieving a decline reaching 69.9%. Our work combines the phase recovery algorithm with the reference of measurement error information from both polarization dimensions, significantly reducing VME and demonstrating the potential of polarized vortex beams in high-precision applications. This innovatively provides, to our knowledge, a novel method and theoretical support for further enhancing the accuracy of free-space rotational velocity measurements.

Simultaneous measurement of multimode squeezing through multimode phase-sensitive amplification

Multimode squeezed light is an increasingly popular tool in photonic quantum technologies, including sensing, imaging, and computation. Meanwhile, the existing methods of its characterization are technically complicated, which reduces the level of squeezing, and mostly deal with a single mode at a time. Here, for the first time, to the best of our knowledge, we employ optical parametric amplification to characterize multiple squeezing eigenmodes simultaneously. We retrieve the shapes and squeezing degrees of all modes at once through direct detection followed by modal decomposition. This method is tolerant to inefficient detection and does not require a local oscillator. For a spectrally and spatially multimode squeezed vacuum, we characterize eight strongest spatial modes, obtaining squeezing and anti-squeezing values of up to −5.2 ± 0.2 dB and 8.6 ± 0.3 dB, respectively, despite the 50% detection loss. This work, being the first exploration of an optical parametric amplifier’s multimode capability for squeezing detection, paves the way for the real-time detection of multimode squeezing.

Chaos from a free-running broad-area VCSEL.

We experimentally report on the detection of chaos from a free-running commercial broad-area vertical-cavity surface-emitting laser (VCSEL) without the need for external perturbation such as optical feedback, injection, or current modulation. The evolution of nonlinear dynamics leading to chaotic behavior is studied, and the system's complexity is characterized using chaos titration and correlation dimension. We link the occurrence of chaos with the complex interplay between the spatial laser mode competition and polarization dynamics.

Spontaneous symmetry breaking of an optical polarization state in a polarization-selective nonlinear resonator.

We exploit polarization self-rotation (PSR) in atomic rubidium vapor to observe spontaneous symmetry breaking and bistability of polarization patterns. We pump the vapor cell with horizontally polarized light while the vertical polarization, which is initially in the vacuum state, is resonated in a ring cavity. Microscopic field fluctuations in this mode experience cumulative gain due to the compound action of amplification due to the self-rotation and feedback through the resonator, eventually acquiring a macroscopic magnitude akin to an optical parametric oscillator. The randomness of these fluctuations results in a bistable, random macroscopic polarization pattern at the output. We propose utilizing this mechanism to simulate an Ising-like interaction between multiple spatial modes and as a basis for a fully optical coherent Ising machine (CIM).

Design and Fabrication of Multi-Magnetron Microwave Oven for High-Temperature Applications

This article examines the design, manufacture, and performance of multi-magnetron ovens capable of reaching high temperatures. Firstly, an appropriate waveguide was simulated, and the production process was completed. Then, the proposed designs for multi-magnetron ovens were simulated, and appropriate dimensions were suggested. It was reported that the average power density (PD) value of the produced multi-magnetron oven was 0.37 mW/cm², which indicates its performance and efficiency. This value was found to be compliant with standards and safe for human use. The main objective of our study was to demonstrate that waveguides can reach high temperatures at the center of the oven without affecting each other. In this context, it was observed that the temperature created by magnetrons operating in single, double, triple, and quadruple modes gradually increased at the center of the oven. The simulation results supporting this showed that the S21 parameter was -177 dB. The design proposed and applied in our study was efficient, easy to produce, safe for human use, low cost, and usable in commercial and academic studies for reaching high temperatures. Overall, the multi-magnetron oven design proved to be a successful and practical solution for applications requiring high temperatures, showcasing its potential for both industrial and research purposes. The findings of this study contribute valuable insights into the development of advanced heating technologies, demonstrating significant improvements in efficiency and safety for high-temperature applications.

Normal Form Formulae of Turing–Turing Bifurcation for Partial Functional Differential Equations With Nonlinear Diffusion

ABSTRACTFor most systems, the appearance of Turing bifurcation means that it is possible to excite Turing–Turing bifurcation, thus inducing superimposed spatial patterns, multistable spatial patterns co‐existing, and others.It is undoubtedly of interest to qualitatively analyze the structures and stability of these spatially heterogeneous solutions generated by Turing–Turing bifurcation. Therefore, in this paper, with the aid of the center manifold theory and the normal form method, for general partial functional differential equations with nonlinear diffusion, the third‐order normal form is firstly derived. It is locally topologically equivalent to the primitive partial functional differential equations at the Turing–Turing bifurcation point. And then the explicit formulae for the coefficients in the normal form associated with three different spatial modes are presented. As an application, a predator–prey model with predator–taxis is considered. It is theoretically revealed that the system admits the coexistence of a pair of stable steady states with a single characteristic wavelength and the coexistence of four stable steady states with different single characteristic wavelengths. Further, the parameter regions in which these phenomena will arise are quantitatively given. It is illustrated that the self‐diffusion of prey and predator–taxis complement each other to promote the formation for the spatially homogeneous distributions of populations.