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ABSTRACTThe lithium niobate on insulator devices confine the light field to submicron size in monocrystalline lithium niobate, to achieve ultra-strong electro-optical interaction and nonlinear optical interaction, and thus extend the frontiers of the photonic research in the past decade. Such devices are manufactured using nano-fabrication technology over the thin-film lithium niobate wafer, which usually stands on a silica insulator layer above the substrate material, including low-loss waveguides, electro-optical modulators, domain engineered structures, high-Q microring resonators and electrical filters etc., and lead to breakthroughs in optical communication, microwave photonics and quantum integration.

Abstract Electronic processors are reaching the physical speed ceiling that heralds the era of optical processors. Multifunctional all-optical logic gates (AOLGs) of massively parallel processing are of great importance for large-scale integrated optical processors with speed far in excess of electronics, while are rather challenging due to limited operation bandwidth and multifunctional integration complexity. Here we for the first time experimentally demonstrate a reconfigurable all-in-one broadband AOLG that achieves nine fundamental Boolean logics in a single configuration, enabled by ultrabroadband (400–4000 nm) plasmon-enhanced thermo-optical nonlinearity (TONL) of liquid-metal Galinstan nanodroplet assemblies (GNAs). Due to the unique heterogeneity (broad-range geometry sizes, morphology, assembly profiles), the prepared GNAs exhibit broadband plasmonic opto-thermal effects (hybridization, local heating, energy transfer, etc.), resulting in a huge nonlinear refractive index under the order of 10−4−10−5 within visual-infrared range. Furthermore, a generalized control-signal light route is proposed for the dynamic TONL modulation of reversible spatial-phase shift, based on which nine logic functions are reconfigurable in one single AOLG configuration. Our work will provide a powerful strategy on large-bandwidth all-optical circuits for high-density data processing in the future.

Abstract Dissipative Kerr soliton (DKS) microcomb has emerged as an enabling technology that revolutionizes a wide range of applications in both basic science and technological innovation. Reliable turnkey operation with sub-optical-cycle and sub-femtosecond timing jitter is key to the success of many intriguing microcomb applications at the intersection of ultrafast optics and microwave electronics. Here we propose an approach and demonstrate the first turnkey Brillouin-DKS frequency comb to the best of our knowledge. Our microresonator-filtered laser design offers essential benefits, including phase insensitivity, self-healing capability, deterministic selection of the DKS state, and access to the ultralow noise comb state. The demonstrated turnkey Brillouin-DKS frequency comb achieves a fundamental comb linewidth of 100 mHz and DKS timing jitter of 1 femtosecond for averaging times up to 56 μs. The approach is universal and generalizable to various device platforms for user-friendly and field-deployable comb devices.

LNOI devices have emerged as prominent contributors to photonic integrated circuits (PICs), benefiting from their outstanding performance in electro-optics, acousto-optics, nonlinear optics, etc. Due to the physical properties and current etching technologies of LiNbO3, slanted sidewalls are typically formed in LNOI waveguides, causing polarization-related mode hybridization and crosstalk. Despite the low losses achieved with fabrication advancements in LNOI, such mode hybridization and crosstalk still significantly limit the device performance by introducing polarization-related losses. In this paper, we propose a vertically etched LNOI construction. By improving the geometrical symmetry in the waveguides, vertical sidewalls could adequately mitigate mode hybridization in common waveguide cross sections. Taking tapers and bends as representatives of PIC components, we then conducted theoretical modeling and simulations, which showed that vertical etching effectively exempts devices from polarization-related mode crosstalk. This not only improves the polarization purity and input mode transmittance but also enables lower polarization-related losses within more compact structures. As a demonstration of fabrication feasibility, we innovatively proposed a two-step fabrication technique, and successfully fabricated waveguides with vertical sidewalls. Such vertical etching technology facilitates the development of next-generation high-speed modulators, nonlinear optical devices, and other advanced photonic devices with lower losses and a smaller footprint, driving further innovations in both academic research and industrial applications.

Periodically poled lithium niobate on insulator (PPLNOI) offers an admirably promising platform for the advancement of nonlinear photonic integrated circuits (PICs). In this context, domain inversion engineering emerges as a key process to achieve efficient nonlinear conversion. However, periodic poling processing of thin-film lithium niobate has only been realized on the chip level, which significantly limits its applications in large-scale nonlinear photonic systems that necessitate the integration of multiple nonlinear components on a single chip with uniform performances. Here, we demonstrate a wafer-scale periodic poling technique on a 4-inch LNOI wafer with high fidelity. The reversal lengths span from 0.5 to 10.17 mm, encompassing an area of ~1 cm2 with periods ranging from 4.38 to 5.51 μm. Efficient poling was achieved with a single manipulation, benefiting from the targeted grouped electrode pads and adaptable comb line widths in our experiment. As a result, domain inversion is ultimately implemented across the entire wafer with a 100% success rate and 98% high-quality rate on average, showcasing high throughput and stability, which is fundamentally scalable and highly cost-effective in contrast to traditional size-restricted chiplet-level poling. Our study holds significant promise to dramatically promote ultra-high performance to a broad spectrum of applications, including optical communications, photonic neural networks, and quantum photonics.

Abstract Fiber components form the standard not only in modern telecommunication but also for future quantum information technology. For high-performance single-photon detection, superconducting nanowire single-photon detectors (SPDs) are typically fabricated on a silicon chip and fiber-coupled for easy handling and usage. The fiber-to-chip interface hinders the SPD from being an all-fiber device for full utilization of its excellent performance. Here, we report a scheme of SPD that is directly fabricated on the fiber tip. A bury-and-planar fabrication technique is developed to improve the roughness of the substrate for all-fiber detectors’ performance for single-photon detection with amorphous molybdenum silicide (MoSi) nanowires. The low material selectivity and universal planar process enable fabrication and packaging on a large scale. Such a detector responds to a broad wavelength range from 405 nm to 1550 nm at a dark count rate of 100 cps. The relaxation time of the response pulse is ~ 15 ns, which is comparable to that of on-chip SPDs. Therefore, this device is free from fiber-to-chip coupling and easy packaging for all-fiber quantum information systems.

We theoretically and experimentally study soliton generation and real-time dynamics via time magnifier in microresonator-filtered fiber lasers, achieving self-starting, broad-bandwidth, high-efficiency, and low-noise soliton microcombs at ≥ 10 GHz.

Here the authors demonstrate spatiotemporal mode-locked dissipative Kerr soliton and enhanced photonic flywheel performances in both the fundamental comb linewidth and DKS timing jitter.

Abstract Archaeological silver artifacts are often found to be brittle because of long-term corrosion. However, the restoration of brittle archaeological silver artifacts by thermal treatment has never been quantitatively and systematically studied due to the lack of sufficient experimental samples. Herein, the simulated Ag–Cu alloy flake samples with intergranular corrosion consistent with those brittle archaeological silver artifacts were prepared through two-step annealing and accelerated aging in Fe(NO3)3 + AgNO3 solution. The changes in the microstructure and mechanical strength (σbb, Eb, and HV) of the brittle samples after thermal treatments were studied with the help of SEM–EDS, metallographic observation, three-point bending tests, and microhardness tests. In addition, the most suitable conditions for the restoration of the brittle samples were summarized by the temperature–time (T-t) map obtained from a series of comprehensive thermal treatments. Moreover, the differences in microstructures and mechanical strength between the brittle samples annealed in an aerobic/anaerobic environment were revealed. This work provides an important reference for the restoration and conservation of brittle archaeological silver artifacts.

Abstract In recent years, 3D technology has been widely used in various aspects of the entire workflow of conservation–restoration. However, in the majority of cases, researchers have mainly relied on 3D technologies to assist the conventional conservation–restoration process, and its advantages have not truly been exploited. In this paper, we applied a combination of digital acquisition, virtual anastylosis, virtual reconstruction, and 3D printing of a transparent reversible prosthesis with slots for the restoration of a gold foil decorated Black Ding bowl collected by the Chifeng Museum of the Inner Mongolia Autonomous Region. While completing the physical/aesthetic restoration of the artifact, the conservation–restoration principles of the integrity and authenticity of cultural heritage, minimal intervention and reversibility were followed to the utmost extent. At the same time, we also conducted preliminary performance tests on the 3D printing material of the prosthesis, and the results showed that the material has excellent mechanical properties and stain resistance, contributing to the long-term, stable preservation of the artifact. This work presents an innovative solution applicable to other pieces of cultural heritage and has high significance for promotion.

Weyl semimetals have interesting band-structure features that lead to unique properties. Here, the authors observe and study high-harmonic generation in type-II Weyl semimetal β-WP2 crystals.

Abstract Antimonene, a new member of monoelemental two‐dimensional crystals composed of antimony atoms, was predicted to possess high stability, as well as outstanding electrical and optical properties. Here, we report on the experimental results of productive, high‐quality synthesis of antimonene quantum dots (AQDs) via liquid‐phase exfoliation. The obtained AQDs exhibited excellent nonlinear saturable absorption. The modulation depth and the saturable intensity were found to be around 3.9% and 10.02 GW/cm2, respectively. By using the AQDs saturable absorber in the 639 nm Pr:YLF laser, stable Q‐switching pulsed laser was realized. The maximum output power was 83 mW and the corresponding pulse width was 255 ns with a pulse repetition rate of 227 kHz. These results suggest that AQDs are a promising candidate for nonlinear optical applications.

Abstract We report the generation of frequency-uncorrelated photon pairs from counter-propagating spontaneous parametric down-conversion in a periodically-poled KTP waveguide. The joint spectral intensity of photon pairs is characterized by measuring the corresponding stimulated process, namely, the difference frequency generation process. The experimental result shows a clear uncorrelated joint spectrum, where the backward-propagating photon has a narrow bandwidth of 7.46 GHz and the forward-propagating one has a bandwidth of 0.23 THz like the pump light. The heralded single-photon purity estimated through Schmidt decomposition is as high as 0.996, showing a perspective for ultra-purity and narrow-band single-photon generation. Such unique feature results from the backward-wave quasi-phase-matching condition and does not has a strict limitation on the material and working wavelength, thus fascinating its application in photonic quantum technologies.

Abstract Qudit entanglement is an indispensable resource for quantum information processing since increasing dimensionality provides a pathway to higher capacity and increased noise resilience in quantum communications, and cluster-state quantum computations. In continuous-variable time–frequency entanglement, encoding multiple qubits per photon is only limited by the frequency correlation bandwidth and detection timing jitter. Here, we focus on the discrete-variable time–frequency entanglement in a biphoton frequency comb (BFC), generating by filtering the signal and idler outputs with a fiber Fabry–Pérot cavity with 45.32 GHz free-spectral range (FSR) and 1.56 GHz full-width-at-half-maximum (FWHM) from a continuous-wave (cw)-pumped type-II spontaneous parametric downconverter (SPDC). We generate a BFC whose time-binned/frequency-binned Hilbert space dimensionality is at least 324, based on the assumption of a pure state. Such BFC’s dimensionality doubles up to 648, after combining with its post-selected polarization entanglement, indicating a potential 6.28 bits/photon classical-information capacity. The BFC exhibits recurring Hong–Ou–Mandel (HOM) dips over 61 time bins with a maximum visibility of 98.4% without correction for accidental coincidences. In a post-selected measurement, it violates the Clauser–Horne–Shimony–Holt (CHSH) inequality for polarization entanglement by up to 18.5 standard deviations with an S-parameter of up to 2.771. It has Franson interference recurrences in 16 time bins with a maximum visibility of 96.1% without correction for accidental coincidences. From the zeroth- to the third-order Franson interference, we infer an entanglement of formation (E of) up to 1.89 ± 0.03 ebits—where 2 ebits is the maximal entanglement for a 4 × 4 dimensional biphoton—as a lower bound on the 61 time-bin BFC’s high-dimensional entanglement. To further characterize time-binned/frequency-binned BFCs we obtain Schmidt mode decompositions of BFCs generated using cavities with 45.32, 15.15, and 5.03 GHz FSRs. These decompositions confirm the time–frequency scaling from Fourier-transform duality. Moreover, we present the theory of conjugate Franson interferometry—because it is characterized by the state’s joint-temporal intensity (JTI)—which can further help to distinguish between pure-state BFC and mixed state entangled frequency pairs, although the experimental implementation is challenging and not yet available. In summary, our BFC serves as a platform for high-dimensional quantum information processing and high-dimensional quantum key distribution (QKD).

Abstract We demonstrate a compact, high efficiency and widely tunable intracavity singly resonant optical parametric oscillator (IC-OPO) based on multichannel periodically poled lithium niobate (PPLN). The IC-OPO is composed of 808 nm pump laser diode (LD), Nd:YVO4 laser and linear OPO. The continuous-wave (CW) mid-infrared (MIR) output laser is tunable from 2.25 to 4.79 μm. The maximum output power exceeds 1.08 W at 3.189 μm at 9.1 W LD pump power and the conversion efficiency is 11.88%. We also build up a prototype with volume of 145 × 85 × 42.5 mm3 and its total weight is less than 2 kg. The measured power stability is 1.3% Root Meat Square (RMS) for a 3 h duration under simulated high temperature conditions of 40 °C. RMS is 2.6% for a 4 h duration when simulated temperature is − 40 °C.

The self-injection-locked diode laser can significantly reduce the linewidth down to a sub-100 kHz level but requires optical filtering that is much narrower than the laser cavity linewidth. Such optical filtering is usually sophisticated and beyond the capability of the normal dielectric coating approach. Here we develop a 0.16 nm narrowband dielectric coating using a Fabry–Perot dielectric filter (HFFPF) for the narrow linewidth self-injection-locked laser demonstration using a cost-effective Fabry–Perot laser diode. Single-longitude-mode output is achieved, with beat linewidth down to ~66 kHz and a high side mode suppression ratio over 60 dB. This setup of self-injection-locked laser is cost-effective for mass production and thus is suitable for various applications such as laser ranging, LIDAR, optical communication, and holographic.

Cyclocarya paliurus (Batal.) Iljinskaja (LCP) leaves have been widely employed in food and traditional medicine for treating hyperlipidaemia and its complications, possibly owing to their antioxidant properties. The aim of the present study is to identify the chemical ingredients of antioxidant extracts from LCP by using UHPLC-Q-Orbitrap-MS/MS-based molecular networking, a very recent and useful tool for annotation of chemical constituents in mixtures. The extraction conditions of antioxidant extracts from LCP were optimised by single-factor analysis and response surface methodology (RSM). The optimised conditions were a methanol concentration of 32%, a liquid-to-solid ratio of 0.4 ml/mg, an extraction temperature of 25°C, and an extraction time of 32 min. Under these conditions, the antioxidant yield was 516.20 ± 28.52 μmol TE/ml. The main active ingredients in the antioxidants were identified by UHPLC-Q-Exactive Orbitrap-MS-based molecular networking. In total, 42 compounds were identified, including 20 flavonoids, 16 quinic acid derivatives, 4 caffeoyl derivatives, and 2 coumaroyl derivatives. The findings of the present work suggest that LCP could be a suitable source of natural antioxidant compounds, which might be applicable in the development of potential pharmaceutical drugs targeting diseases related to oxidative stress.

Optical quantum network plays an important role in large scale quantum communication. However, different components for photon generation, transmission, storage and manipulation in network usually cannot interact directly due to the wavelength and bandwidth differences, and thus interfaces are needed to overcome such problems. We propose an optical interface for frequency down-conversion and bandwidth compression based on the counter-propagating quasi-phase-matching difference frequency generation process in the periodically-poled lithium niobate on insulator waveguide. We prove that a separable spectral transfer function can be obtained only by choosing proper pump bandwidth, thus relaxing the limitation of material, dispersion, and working wavelength as a result of the counter-propagation phase-matching configuration. With numerical simulations, we show that our design results in a nearly separable transfer function with the Schmidt number very close to 1. With proper pump bandwidth, an photon at central wavelength of 550 nm with a bandwidth ranging from 50 GHz to 5 THz can be converted to a photon at central wavelength of 1,545 nm with a much narrower bandwidth of 33 GHz.

Mid-infrared (MIR) radiation is essential for remote gas sensing, ranging, and lidar applications, where high pulse energy and narrow linewidth are the keys to the high sensitivity over long distance. However, complex optical and electronic locking schemes are normally required to achieve both features at the same time. Here, we demonstrate pulse-pumped single-longitudinal-mode (SLM) MIR generation using a microresonator seed in the form of a sheet optical parametric oscillator (SOPO). The SOPO features a sub-coherence-length thickness of 400 µm, which enables SLM and high-energy oscillation using cavity phase matching. Its output around 1.55 µm is seeded into an optical parametric amplifier and locks the MIR output in SLM at 3.38 µm. In a simple and compact setup, up to 21% conversion efficiency and 22% slope efficiency are measured with a MIR output energy of 54 µJ. This SLM MIR source with the SOPO seed greatly reduces the system size and is compatible for further integration for field-deployable devices and thus has broad applications in the field of remote gas sensing.

In recent years, with the excavation of an increasing amount of gold and silver artifacts, there has been an urgent need to optimize the formulations and methods of metallographic etching. Herein, a kinetic control study is performed to investigate the mechanisms leading to poor results when etching ancient gold materials with aqua regia, i.e., when secondary AgCl impurities form during the etching of the sample surface. To this end, a concentrated ammonia and sodium thiosulfate solution is used to dissolve AgCl impurities and obtain high-quality metallographic images of ancient gold materials using a coordination reaction to generate stable free-state coordination ions from Ag+. On this basis, a ferric chloride + sodium thiosulfate method is proposed to optimize the formulation of the etchant for ancient silver materials. The formulation is efficient, safe and easy to handle, and solves the problems of the easy failure of the commonly used etchant of ammonia + hydrogen peroxide and the complicated preparation process of acidified potassium dichromate while maintaining the long-term stability of the etched Ag–Cu alloy samples.

The coherent superposition of position states in a quantum walk (QW) can be precisely engineered towards the desired distributions to meet the need of quantum information applications. The coherent distribution can make full use of quantum parallel in computation and simulation. Particularly, the uniform superposition provides the robust nonlocality, which has wide applications such as the generation of genuine multibit random numbers without postprocessing. We experimentally demonstrate that the rich dynamics featured with arbitrary coherent distributions can be obtained by introducing different sets of the time- and position-dependent operations. Such a QW is realized by a resource-constant and flexible optical circuit, in which the variable operation is executed based on a Sagnac interferometer in an intrinsically stable and precisely controlled way. Our results contribute to the practical realization of quantum-walk-based quantum computation, quantum simulations, and quantum information protocols.

Hyperparametric oscillation is essential for coherent optical signal generation in a broad wavelength range. Integration in a compact system, such a broadband light source, is of special interest for practical applications requiring field-deployable spectroscopy devices. Here we demonstrate an all-fiber hyperparametric oscillation source based on four-wave mixing in a high-Q fiber Fabry–Pérot (FFP) microresonator. Assisted by the Raman effect, the generated optical signal spans over 400 nm with fine line-to-line spacing of 667 MHz. The compatibility of this FFP microresonator enables a robust and reliable all-fiber system through a splicing technique and fiber connectors. Such a plug-and-play platform is convenient and efficient for broad applications in optical communications and spectroscopy.

Optical microcavities have been widely used in nonlinear optics, quantum optics, and laser technologies. Here we demonstrate the self-injection locking of a distributed feedback diode laser using home-made high-finesse Fabry-Perot microcavity. The Fabry-Perot microcavity is fabricated from an x-cut lithium niobate crystal with highly reflective coatings. Frequency pulling effect can be observed for a successful locking, and results in a single-longitudinal mode lasing with narrow linewidth. The lasing wavelength and output power are found robust to the laser-diode current and temperature variations, in comparison to the free-running case. We further characterize the laser linewidth with beat note measurement with a high-performance external cavity diode laser, with beat-note linewidth of 601.85 kHz. This results shows a new method for laser frequency stabilization in a simple setup, and may find applications in telecommunication and spectroscopy.

We demonstrate here a compact optical parametric oscillator module for mid-infrared generation via nonlinear frequency conversion. This module weighs only 2.5 kg and fits within a small volume of 220 × 60 × 55 mm3. The module can be easily aligned to various pump laser sources, and here we use a 50 W ytterbium (Yb)-doped fiber laser as an example. With a two-channel MgO-doped periodically poled lithium niobate crystal (MgO:PPLN), our module covers a tuning range of 2416.17–2932.25 nm and 3142.18–3452.15 nm. The highest output power exceeds 10.4 W at 2.7 μm, corresponding to a conversion efficiency of 24%. The measured power stability is 2.13% Root Meat Square (RMS) for a 10 h duration under outdoor conditions.