Four-channel CWDM transmitter chip based on thin-film lithium niobate platform

Multi-lane integrated transmitter chips are key components in future compact optical modules to realize high-speed optical interconnects.Thin-film lithium niobate(TFLN)photonics have emerged as a promising platform for achieving high-performance chip-scale optical systems.Combining a coarse wavelength-division multiplexing(CWDM)devices using fabrication-tolerant angled multimode interferometer structure and high-performance electro-optical modulators,we demonstrate monolithic on-chip four-channel CWDM transmitter on the TFLN platform for the first time.The four-channel CWDM transmitter enables high-speed transmissions of 100 Gb/s data rate per wavelength channel(i.e.,an aggregated date rate of 400 Gb/s).

Quantification methodologies on organization and morphology features of fiber-like structures:A review

Among all the structural formations,fiber-like structure is one of the most common modalities in organisms that undertake essential functions.Alterations in spatial organization of fibrous structures can refiect information of physiological and pathological activities,which is of significance in both researches and clinical applications.Hence,the quantification of subtle changes in fiber-like structures is potentiallymeaningful in studying structure-function relationships,disease progression,carcinoma staging and engineered tissue remodeling.In this study,we examined a wide range of methodologies that quantify organizational and morphological features of fibrous structures,including orientation,alignment,waviness and thickness.Each method was demonstrated with specific applications.Finally,perspectives of future quantification analysis techniques were explored.

A review and a statistical analysis of porosity in metals additively manufactured by laser powder bed fusion

Additive manufacturing(AM), or 3D printing, is an emerging technology that “adds” materials up and constructs products through a layer-by-layer procedure. Laser powder bed fusion(LPBF) is a powder-bed-based AM technology that can fabricate a large variety of metallic materials with excellent quality and accuracy. However, various defects such as porosity,cracks, and incursions can be generated during the printing process. As the most universal and a near-inevitable defect,porosity plays a substantial role in determining the mechanical performance of as-printed products. This work presents a comprehensive review of literatures that focused on the porosity in LPBF printed metals. The formation mechanisms,evaluation methods, effects on mechanical performance with corresponding models, and controlling methods of porosity have been illustrated and discussed in-depth. Achievements in four representative metals, namely Ti-6Al-4V, 316L, Inconel 718, and Al Si10Mg, have been critically reviewed with a statistical analysis on the correlation between porosity fraction and tensile properties. Ductility has been determined as the most sensitive property to porosity among several key tensile properties. This review also provides potential directions and opportunities to address the current porosity-related challenges.

Three-dimensional remodeling of collagen fibers within cervical tissues in pregnancy

The cervix is a collagen-rich connective tissue that must remain closed during pregnancy while undergoing progressive remodeling in preparation for delivery,which begins before the onset of the preterm labor process.Therefore,it is important to resolve the changes of collagen flbers during cervical remodeling for the prevention of preterm labor.Herein,we assessed the spatial organization of collagen flbers in a three-dimensional(3D)context within cervical tissues of mice on day 3,9,12,15 and 18 of gestation.We found that the 3D directional variance,a novel metric of alignment,was higher on day 9 than that on day 3 and then gradually decreased from day 9 to day 18.Compared with two-dimensional(2D)approach,a higher sensitivity was achieved from 3D analysis,highlighting the importance of truly 3D quantification.Moreover,the depthdependent variation of 3D directional variance was investigated.By combining multiple 3D directional variance-derived metrics,a high level of classification accuracy was acquired in distinguishing different periods of pregnancy.These results demonstrate that 3D directional variance is sensitive to remodeling of collagen fibers within cervical tissues,shedding new light on highly-sensitive,early detection of preterm birth(PTB).

Zeolite-mediated hybrid Cu^(+)/Cu~0 interface for electrochemical nitrate reduction to ammonia

The electrocatalytic conversion of reactive nitrogen species to ammonia is a promising strategy for efficient NH_(3) synthesis.In this study,we reveal that the hybrid Cu^(+)/Cu~0 interface is catalytically active for electrochemical ammonia synthesis from nitrate reduction.To maintain the hybrid Cu^(+)/Cu~0 state at negative reaction potentials,hydrophilic zeolite is used to modify Cu/Cu_(2)O electrocatalyst,which demonstrates an impressive NH_(3) production rate of 41.65 mg h^(-1) cm^(-2)with ~100% Faradaic efficiency of ammonia synthesis at-0.6 V vs.RHE.In-situ Raman spectroscopy unveil the high activity originates from the zeolite reconstruction at the electrode–electrolyte interface,which protects the valence state of Cu~0/Cu^(+) site under negative potential and promotes electrochemical activity towards NH_(3) synthesis.

Fundamentals and applications of photonic waveguides with bound states in the continuum

Photonic waveguides are the most fundamental element for photonic integrated circuits(PICs).Waveguide properties,such as propagation loss,modal areas,nonlinear coefficients,etc.,directly determine the functionalities and performance of PICs.Recently,the emerging waveguides with bound states in the continuum(BICs)have opened new opportunities for PICs because of their special properties in resonance and radiation.Here,we review the recent progress of PICs composed of waveguides with BICs.First,fundamentals including background physics and design rules of a BIC-based waveguide will be introduced.Next,two types of BIC-based waveguide structures,including shallowly etched dielectric and hybrid waveguides,will be presented.Lastly,the challenges and opportunities of PICs with BICs will be discussed.

Realization of advanced passive silicon photonic devices with subwavelength grating structures developed by efficient inverse design

Compact passive silicon photonic devices with high performance are always desired for future largescale photonic integration.Inverse design provides a promising approach to realize new-generation photonic devices,while it is still very challenging to realize complex photonic devices for most inverse designs reported previously due to the limits of computational resources.Here,we present the realization of several representative advanced passive silicon photonic devices with complex optimization,including a sixchannel mode(de)multiplexer,a broadband 90 deg hybrid,and a flat-top wavelength demultiplexer.These devices are designed inversely by optimizing a subwavelength grating(SWG)region and the multimode excitation and the multimode interference are manipulated.Particularly,such SWG structures are more fabrication-friendly than those random nanostructures introduced in previous inverse designs.The realized photonic devices have decent performances in a broad bandwidth with a low excess loss of<1 dB,which is much lower than that of previous inverse-designed devices.The present inverse design strategy shows great effectiveness for designing advanced photonic devices with complex requirements(which is beyond the capability of previous inverse designs)by using affordable computational resources.

Reconfigurable optical add-drop multiplexers for hybrid mode-/wavelength-division-multiplexing systems

Dealing with the increase in data workloads and network complexity requires efficient selective manipulation of any channels in hybrid mode-/wavelength-division multiplexing(MDM/WDM)systems.A reconfigurable optical add-drop multiplexer(ROADM)using special modal field redistribution is proposed and demonstrated to enable the selective access of any mode-/wavelength-channels.With the assistance of the subwavelength grating structures,the launched modes are redistributed to be the supermodes localized at different regions of the multimode bus waveguide.Microring resonators are placed at the corresponding side of the bus waveguide to have specific evanescent coupling of the redistributed supermodes,so that any mode-/wavelength-channel can be added/dropped by thermally tuning the resonant wavelength.As an example,a ROADM for the case with three mode-channels is designed with low excess losses of<0.6,0.7,and 1.3 dB as well as low cross talks of<−26.3,−28.5,and−39.3 dB for the TE0,TE1,and TE2 modes,respectively,around the central wavelength of 1550 nm.The data transmission of 30 Gbps∕channel is also demonstrated successfully.The present ROADM provides a promising route for data switching/routing in hybrid MDM/WDM systems.

Achieving ultra-high strength and ductility in Mg–9Al–1Zn–0.5Mn alloy via selective laser melting

Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting(SLM)technology is quite difficult owing to the poor weldability and low boiling point.To address these challenges and seek the optimal processing parameters,response surface methodology was systematically utilized to determine the appropriate SLM parameter combinations.Mg–9Al–1Zn–0.5Mn sample with high relative density(99.5±0.28%)and favorable mechanical properties(microhardness=95.6±5.28 HV_(0.1),UTS=370.2 MPa,and At=10.4%)was achieved using optimized SLM parameters(P=120 W,v=500 mm/s,and h=45μm).Sample is dominated by a random texture and microstructure is primarily constituted by quantities offine equiaxed grains(α-Mg phase),a small amount ofβ-Al_(12)Mg_(17) structures(4.96 vol%,including spherical:[2110]_(α)//[111]_(β)and long lath-like:[2110]_(α)//[115]_(β)or[1011]_(α)//[321]_(β)),and some short rod-shaped Al8Mn5 nanoparticles.Benefiting from grain boundary strengthening,solid solution strengthening,and precipitation hardening of various nanoparticles(β-Al12Mg17 and Al8Mn5),high-performance Mg–9Al–1Zn–0.5Mn alloy biomedical implants can be fabricated.Precipitation hardening dominates the strengthening mechanism of the SLM Mg–9Al–1Zn–0.5Mn alloy.

Generating a nanoscale blade-like optical field in a coupled nanofiber pair

An optical field with sub-nm confinement is essential for exploring atomic-or molecular-level light-matter interaction.While such fields demonstrated so far have typically point-like cross-sections,an optical field having a higher-dimensional cross-section may offer higher flexibility and/or efficiency in applications.Here,we propose generating a nanoscale blade-like optical field in a coupled nanofiber pair(CNP)with a 1-nm-width central slit.Based on a strong mode coupling-enabled slit waveguide mode,a sub-nm-thickness blade-like optical field can be generated with a cross-section down to~0.28 nm×38 nm at 1550 nm wavelength(i.e.,a thickness of~λ_(0)∕5000)and a peak-to-background intensity ratio(PBR)higher than 20 d B.The slit waveguide mode of the CNP can be launched from one of the two nanofibers that are connected to a standard optical fiber via an adiabatical fiber taper,in which a fundamental waveguide mode of the fiber can be converted into a high-purity slit mode with high efficiency(>98%)within a CNP length of less than 10μm at 1550 nm wavelength.The wavelengthdependent behaviors and group velocity dispersion in mode converting processes are also investigated,showing that such a CNP-based design is also suitable for broadband and ultrafast pulsed operation.Our results may open up new opportunities for studying light-matter interaction down to the sub-nm scale,as well as for exploring ultra-high-resolution optical technology ranging from super-resolution nanoscopy to chemical bond manipulation.

Optical microfiber or nanofiber:a miniature fiber-optic platform for nanophotonics

An optical micro/nanofiber(MNF)is a quasi-one-dimensional free-standing optical waveguide with a diameter close to or less than the vacuum wavelength of light.Combining the tiny geometry with highrefractive-index contrast between the core and the surrounding,the MNF exhibits favorable optical properties such as tight optical confinement,strong evanescent field,and large-diameter-dependent waveguide dispersion.Meanwhile,as a quasi-one-dimensional structure with extraordinarily high geometric and structural uniformity,the MNF also has low optical loss and high mechanical strength,making it favorable for manipulating light on the micro/nanoscale with high flexibility.Over the past two decades,optical MNFs,typically being operated in single mode,have been emerging as a miniaturized fiber-optic platform for both scientific research and technological applications.In this paper,we aim to provide a comprehensive overview of the representative advances in optical MNFs in recent years.Starting from the basic structures and fabrication techniques of the optical MNFs,we highlight linear and nonlinear optical and mechanical properties of the MNFs.Then,we introduce typical applications of optical MNFs from nearfield optics,passive optical components,optical sensors,and optomechanics to fiber lasers and atom optics.Finally,we give a brief summary of the current status of MNF optics and technology,and provide an outlook into future challenges and opportunities.

Generative pre-trained transformers(GPT)-based automated data mining for building energy management:Advantages,limitations and the future

Advanced data mining methods have shown a promising capacity in building energy management.However,in the past decade,such methods are rarely applied in practice,since they highly rely on users to customize solutions according to the characteristics of target building energy systems.Hence,the major barrier is that the practical applications of such methods remain laborious.It is necessary to enable computers to have the human-like ability to solve data mining tasks.Generative pre-trained transformers(GPT)might be capable of addressing this issue,as some GPT models such as GPT-3.5 and GPT-4 have shown powerful abilities on interaction with humans,code generation,and inference with common sense and domain knowledge.This study explores the potential of the most advanced GPT model(GPT-4)in three data mining scenarios of building energy management,i.e.,energy load prediction,fault diagnosis,and anomaly detection.A performance evaluation framework is proposed to verify the capabilities of GPT-4 on generating energy load prediction codes,diagnosing device faults,and detecting abnormal system operation patterns.It is demonstrated that GPT-4 can automatically solve most of the data mining tasks in this domain,which overcomes the barrier of practical applications of data mining methods in this domain.In the exploration of GPT-4,its advantages and limitations are also discussed comprehensively for revealing future research directions in this domain.

Parallel fabrication of silica optical microfibers and nanofibers

Optical micro/nanofibers(MNFs)taper-drawn from silica fibers possess intriguing optical and mechanical properties.Recently,MNF array or MNFs with identical geometries have been attracting more and more attention,however,current fabrication technique can draw only one MNF at a time,with a low drawing speed(typically 0.1 mm/s)and a complicated process for high-precision control,making it inefficient in fabricating multiple MNFs.Here,we propose a parallel-fabrication approach to simultaneously drawing multiple(up to 20)MNFs with almost identical geometries.For fiber diameter larger than 500 nm,measured optical transmittances of all as-drawn MNFs exceed 96.7%at 1550-nm wavelength,with a diameter deviation within 5%.Our results pave a way towards high-yield fabrication of MNFs that may find applications from MNF-based optical sensors,optical manipulation to fiber-to-chip interconnection.

Anisotropy-free arrayed waveguide gratings on X-cut thin film lithium niobate platform of in-plane anisotropy

Arrayed waveguide grating is a versatile and scalable integrated light dispersion device,which has been widely adopted in various applications,including,optical communications and optical sensing.Recently,thin-film lithium niobate emerges as a promising photonic integration platform,due to its ability of shrinking largely the size of typical lithium niobate based optical devices.This would also enable multifunctional photonic integrated chips on a single lithium niobate substrate.However,due to the intrinsic anisotropy of the material,to build an arrayed waveguide grating on X-cut thin-film lithium niobate has never been successful.Here,a universal strategy to design anisotropyfree dispersive components on a uniaxial in-plane anisotropic photonic integration platform is introduced for the first time.This leads to the first implementation of arrayed waveguide gratings on X-cut thin-film lithium niobate with various configurations and high-performances.The best insertion loss of 2.4 dB and crosstalk of−24.1 dB is obtained for the fabricated arrayed waveguide grating devices.Applications of such arrayed waveguide gratings as a wavelength router and in a wavelength-division multiplexed optical transmission system are also demonstrated.

Atomization characteristics of pyrolysis oil derived from waste tires

The atomization characteristics play a key role in the highly efficient combustion of pyrolysis oil derived from waste tires.In this study,the fuel properties of tire pyrolysis oil(TPO)were initially studied,and then a high-speed camera and a phase Doppler particle analyzer were employed to characterize the atomization feature of TPO.The influence of pressure and nozzle orifice diameter on atomization characteristics such as spray angle,droplet velocity,and droplet size distribution was investigated.The results showed that TPO had a high calorific value of about 43.6 MJ/kg and a low viscosity of 3.84×10^(–6)m^(2)/s at 40℃,which made it have the potential to be used as an alternative fuel.Higher pressure expanded the spray angle and extended the spray in both the axial and radial directions.With increasing pressure,spray angle and droplet velocity raised,and the increase in crushing effect of air reduced the Sauter mean diameter(SMD)of the droplets.To obtain proper atomization quality for combustion,the pressure is expected to be higher than 1.25 MPa.With increasing nozzle orifice diameter,droplet velocity increased,and the SMD of the droplets increased as well due to weakened crushing effect of the orifice.Therefore,the pressure must be increased to maintain the atomization quality when using a nozzle with a larger orifice.Due to the lower viscosity,the velocity and particle size distribution of TPO droplets after atomization were smaller than those of diesel droplets.The extremely small carbon black contained in TPO also contributed to the breaking of droplets and played a certain role in the size reduction of the oil droplets,but it may cause the risk of nozzle blockage.In summary,TPO showed great atomization characteristics for alternative fuel applications.

Recent progress on the applications of micro/nanofibers in ultrafast optics

Ultrafast fiber lasers are indispensable components in the field of ultrafast optics,and their continuous performance advancements are driving the progress of this exciting discipline.Micro/Nanofibers(MNFs)possess unique properties,such as a large fractional evanescent field,flexible and controllable dispersion,and high nonlinearity,making them highly valuable for generating ultrashort pulses.Particularly,in tasks involving mode-locking and dispersion and nonlinearity management,MNFs provide an excellent platform for investigating intriguing nonlinear dynamics and related phenomena,thereby promoting the advancement of ultrafast fiber lasers.In this paper,we present an introduction to the mode evolution and characteristics of MNFs followed by a comprehensive review of recent advances in using MNFs for ultrafast optics applications including evanescent field modulation and control,dispersion and nonlinear management techniques,and nonlinear dynamical phenomenon exploration.Finally,we discuss the potential application prospects of MNFs in the realm of ultrafast optics.

Cross-level steam load smoothing and optimization in industrial parks using data-driven approaches

This study focuses on the integrated energy production system in industrial parks, addressing the problem of stable load dispatch of equipment under demand fluctuations. A cross-level method for steam load smoothing and optimization is proposed, aiming to achieve stable production and optimal economic performance through three levels of integration: load forecasting, load dispatch, and load regulation. Unlike traditional methods that directly use load forecasting values, heat network elasticity is presented as a buffer between demand and supply. Constraints for minimal changes in equipment load and operational parameters are established for smooth regulation. Industrial cases demonstrate that the load forecasting model has mean absolute percentage errors of 2.44% and 1.68% for medium-pressure and low-pressure steam, respectively, meeting accuracy requirements. The modified supply-side load smoothness is effectively improved by considering heat network elasticity. The method increases boiler efficiency by 1.92%, reducing average coal consumption by 0.92 t/h. Compared to manual operation, the proposed model leads to an average increase of 5.69 MW in power generation and an average reduction of 10.81% in coal-to-electricity ratio. This study verifies the importance of smooth integration across different levels and analyzes the effective response of the proposed method to the uncertainty in load forecasting. The method demonstrates the enormous potential of data-driven methods in achieving safe, economical, and sustainable production in industrial parks.

Component modeling and updating method of integrated energy systems based on knowledge distillation

Amid the backdrop of carbon neutrality, traditional energy production is transitioning towards integrated energy systems (IES), where model-based scheduling is key in scenarios with multiple uncertainties on both supply and demand sides. The development of artificial intelligence algorithms, has resolved issues related to model accuracy. However, under conditions of high proportion renewable energy integration, component load adjustments require increased flexibility, so the mathematical model of the component must adapt to constantly changing operating conditions. Therefore, the identification of operating condition changes and rapid model updating are pressing issues. This study proposes a modeling and updating method for IES components based on knowledge distillation. The core of this modeling method is the light weighting of the model, which is achieved through a knowledge distillation method, using a teacher-student mode to compress complex neural network models. The triggering of model updates is achieved through principal component analysis. The study also analyzes the impact of model errors caused by delayed model updates on the overall scheduling of IES. Case studies are conducted on critical components in IES, including coal-fired boilers and turbines. The results show that the time consumption for model updating is reduced by 76.67 % using the proposed method. Under changing conditions, compared with two traditional models, the average deviation of this method is reduced by 12.61 % and 3.49 %, respectively, thereby improving the model's adaptability. The necessity of updating the component model is further analyzed, as a 1.00 % mean squared error in the component model may lead to a power deviation of 0.075 MW. This method provides real-time, adaptable support for IES data modeling and updates.

Robust thin-film lithium niobate modulator on a silicon substrate with backside holes

Recently,Mach–Zehnder modulators based on thin-film lithium niobate have attracted broad interest for their potential for high modulation bandwidth,low insertion loss,high extinction ratio,and high modulation efficiency.The periodic capacitively loaded traveling-wave electrode is optimally adopted for ultimate high-performances in this type of modulator.However,such an electrode structure on a silicon substrate still suffers from the velocity mismatch and substrate leakage loss for microwave signals.Here,we introduce a thin-film lithium niobate modulator structure using this periodic capacitively loaded electrode on a silicon substrate.Backside holes in the silicon substrate are prepared to solve robustly the above difficulties.The fabricated device exhibits an insertion loss of 0.9 dB,a halfwave-voltage–length product of 2.18 V·cm,and an ultra-wide bandwidth well exceeding 67 GHz for a 10-mm-long device.Data transmissions with rates up to 112 Gb/s are demonstrated.The proposed structure and fabrication strategy are compatible for other types of monolithic and heterogeneous integrated thin-film lithium niobate modulators on a silicon substrate.

Silicon photonic spectrometer with multiple customized wavelength bands

A silicon photonic spectrometer with multiple customized wavelength bands is developed by introducing multiple channels of wideband optical filters based on multimode waveguide gratings(MWGs)for pre-filtering and the corresponding thermally tunable narrowband filter for high resolution.For these multiple customized wavelength bands,the central wavelengths,bandwidths,and resolutions are designed flexibly as desired,so that the system is simplified and the footprint is minimized for several practical applications(e.g.,gas sensing).A customized silicon photonic spectrometer is designed and demonstrated experimentally with four wavelength bands centered around1310 nm,1560 nm,1570 nm,and 1930 nm,which is,to the best of our knowledge,the first on-chip spectrometer available for sensing multiple gas components like HF,CO,H_(2)S,and CO_(2).The spectral resolutions of the four wavelength bands are 0.11 nm,0.08 nm,0.08 nm,and 0.37 nm,respectively.Such a customized silicon photonic spectrometer shows great potential for various applications,including gas monitors,wearable biosensors,and portable spectral-domain optical coherence tomography.