Chalcogenide As₂S₃Sidewall Bragg Gratings Integrated on LiNbO₃Substrate

This paper introduces the design and applications of integrated As2S3 sidewall Bragg gratings on LiNbO3 substrate. The grating reflectance and bandwidth are analyzed with coupled-mode theory. Coupling coefficients are computed by taking overlap integration. Numerical results for uniform gratings, phase-shifted gratings and grating cavities as well as electro-optic tunable gratings are presented. These integrated As2S3 sidewall gratings on LiNbO3 substrate provide an approach to the design of a wide range of integrated optical devices including switches, laser cavities, modulators, sensors and tunable filters.

Multiwavelength Actively Mode-locked Fiber Laser with a Double-ring Configuration and Integrated Cascaded Sampled Fiber Bragg Gratings

A modified multiwavelength actively mode-locked fiber ring laser is proposed and experimentally demonstrated. In this kind of laser, stable multiwavelengths lasing is achieved by integrating cascaded sampled fiber Bragg gratings(SFBGs) into the laser cavity. To implement actively mode-locking technique, a double-ring cavity configuration is used to assure that the cavity lengths for all wavelengths lasing are identical. Thus, simultaneous mode locking of all wavelengths has been successfully achieved by using the same mode-locking signal.

Industrial utilization of arsenic-containing gold dressing tailings as pellet prepared by straight grate process

The utilization of arsenic-containing gold dressing tailings is an urgent issue faced by gold production companies worldwide.The thermodynamic analysis results indicate that ferrous arsenate(FeAsO_(4)),pyrite(FeS_(2))and sodium cyanide(NaCN)in the arsenic-containing gold metallurgical tailings can be effectively removed using straight grate process,and the removal of pyrite and sodium cyanide is basically completed during the preheating stage,while the removal of ferrous arsenate requires the roasting stage.The pellets undergo a transformation from magnetite to hematite during the preheating process,and are solidified through micro-crystalline bonding and high-temperature recrystallization of hematite(Fe_(2)O_(3))during the roasting process.Ultimately,pellets with removal rates of 80.77% for arsenic,88.78% for sulfur,and 99.88% for cyanide are obtained,as well as the iron content is 61.1% and the compressive strength is 3071 N,meeting the requirements for blast furnace burden.This study provides an industrially feasible method for treating arsenic-containing gold smelting tailings,benefiting gold production enterprises.

Theory and verification of moiréfringes for x-ray three-phase grating interferometer

Dual-phase and three-phase grating x-ray interference is a promising new technique for grating-based x-ray differential phase contrast imaging.Dual-phase grating interferometers have been relatively completely studied and discussed.In this paper,the corresponding imaging fringe formula of the three-phase grating interferometer is provided.At the same time,the similarities and differences between the three-phase grating interferometer and the dual-phase grating interferometer are investigated and verified,and that the three-phase grating interferometer can produce large-period moiréfringes without using the analyzing grating is demonstrated experimentally.Finally,a simple method of designing three-phase grating and multi-grating imaging systems from geometric optics based on the thin-lens theory of gratings is presented.These theoretical formulas and experimental results provide optimization tools for designing three-phase grating interferometer systems.

Enhancing the Goos-Hänchen shift based on quasi-bound states in the continuum through material asymmetric dielectric compound gratings

Quasi-bound state in the continuum(QBIC)resonance is gradually attracting attention and being applied in Goos-Hänchen(GH)shift enhancement due to its high quality(Q)factor and superior optical confinement.Currently,symmetry-protected QBIC resonance is often achieved by breaking the geometric symmetry,but few cases are achieved by breaking the material symmetry.This paper proposes a dielectric compound grating to achieve a high Q factor and high-reflection symmetry-protectede QBIC resonance based on material asymmetry.Theoretical calculations show that the symmetry-protected QBIC resonance achieved by material asymmetry can significantly increase the GH shift up to-980 times the resonance wavelength,and the maximum GH shift is located at the reflection peak with unity reflectance.This paper provides a theoretical basis for designing and fabricating high-performance GH shift tunable metasurfaces/dielectric gratings in the future.

975 nm multimode semiconductor lasers with high-order Bragg diffraction gratings

The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD)with high-order diffraction grat-ings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maxi-mum(FWHM)is less than 0.5 nm.The results demonstrate that the designed high-order surface gratings can effectively nar-row the spectral width of multimode semiconductor lasers at high output power.

Monitoring shear deformation of sliding zone via fiber Bragg grating and particle image velocimetry

Monitoring shear deformation of sliding zones is of great significance for understanding the landslide evolution mechanism,in which fiber optic strain sensing has shown great potential.However,the cor-relation between strain measurements of quasi-distributed fiber Bragg grating(FBG)sensing arrays and shear displacements of surrounding soil remains elusive.In this study,a direct shear model test was conducted to simulate the shear deformation of sliding zones,in which the soil internal deformation was captured using FBG strain sensors and the soil surface deformation was measured by particle image velocimetry(PIV).The test results show that there were two main slip surfaces and two secondary ones,developing a spindle-shaped shear band in the soil.The formation of the shear band was successfully captured by FBG sensors.A sinusoidal model was proposed to describe the fiber optic cable deformation behavior.On this basis,the shear displacements and shear band widths were calculated by using strain measurements.This work provides important insight into the deduction of soil shear deformation using soil-embedded FBG strain sensors.

Waveguide Bragg Grating for Fault Localization in PON

Femtosecond laser direct inscription is a technique especially useful for prototyping purposes due to its distinctive advantages such as high fabrication accuracy,true 3D processing flexibility,and no need for mold or photomask.In this paper,we demonstrate the design and fabrication of a planar lightwave circuit(PLC)power splitter encoded with waveguide Bragg gratings(WBG)using a femtosecond laser inscription technique for passive optical network(PON)fault localization application.Both the reflected wavelengths and intervals of WBGs can be conveniently tuned.In the experiment,we succeeded in directly inscribing WBGs in 1×4 PLC splitter chips with a wavelength interval of about 4 nm and an adjustable reflectivity of up to 70% in the C-band.The proposed method is suitable for the prototyping of a PLC splitter encoded with WBG for PON fault localization applications.

High-performance silicon arrayed-waveguide grating (de)multiplexer with 0.4-nm channel spacing

A high-performance silicon arrayed-waveguide grating(AWG)with 0.4-nm channel spacing for dense wavelength-division multiplexing systems is designed and realized successfully.The device design involves broadening the arrayed waveguides far beyond the single-mode regime,which minimizes random phase errors and propagation loss without requiring any additional fabrication steps.To further enhance performance,Euler bends have been incorporated into the arrayed waveguides to reduce the device’s physical footprint and suppress the excitation of higher modes.In addition,shallowly etched transition regions are introduced at the junctions between the free-propagation regions and the arrayed waveguides to minimize mode mismatch losses.As an example,a 32×32 AWG(de)multiplexer with a compact size of 900μm×2200μm is designed and demonstrated with a narrow channel spacing of 0.4 nm by utilizing 220-nm-thick silicon photonic waveguides.The measured excess loss for the central channel is∼0.65 dB,the channel nonuniformity is around 2.5 dB,while the adjacent-channel crosstalk of the central output port is−21.4 dB.To the best of our knowledge,this AWG(de)multiplexer is the best one among silicon-based implementations currently available,offering both dense channel spacing and a large number of channels.

Strain-Insensitive Fiber Bragg Grating Composite Structure for Wide-Range Temperature Sensing

This paper reports on the design,fabrication,and temperature strain sensing performance of a fiber Bragg grating composite structure for surface mounted temperature measurements over a wide temperature range,with highly reduced strain cross-sensitivity.The fiber Bragg grating sensor is encapsulated in a polyimide tube filled with epoxy resin,forming an arc-shaped cavity.This assembly is then placed between two layers of glass fiber prepreg with a flexible pad in between and cured into shape.Experimental results,supported by finite element simulations,demonstrate an enhanced temperature sensitivity is 26.3 pm/°C over a wide temperature range of–30°C to 70°C,and high strain transfer isolation of about 99.65%.

基于物联网和弱反射光栅阵列的地质灾害监测系统设计与应用

我国是世界上地质灾害类型最多、地质灾害最严重的国家之一,而雨量监测和形变监测在地质灾害监测中发挥着越来越重要的作用,因此确保地质灾害监测系统的长期运行以及在降雨期间的稳定运行尤为重要。文中基于STM32微控制器、LORA模块、4G模块设计了一款物联网数据采集控制板,并结合压电式雨量传感器、拉绳位移传感器研制了雨量智能监测仪、裂缝位移智能监测仪;结合物联网数据采集控制板和弱反射光栅阵列传感技术构建了基于物联网的弱反射光栅地质灾害监测系统,实现了对地质灾害体的定时监测和降雨期间的自动监测;最后将雨量智能监测仪、裂缝位移智能监测仪和弱反射光栅地质灾害监测系统应用于桐梓县大河镇新场火车站新场滑坡、崩塌的监测实验中。监测数据表明,弱反射光栅监测系统测得传感光缆41#弱反射光栅传感段的位移变化达5 mm,在其附近的位移监测仪也测到有位移变化,可有效实现对地质灾害的定时监测和降雨期间的自动监测。

轻钢格栅混凝土组合墙体抗压性能研究

轻钢格栅混凝土组合墙体的抗压性能研究是该种新型结构应用和发展的关键问题。为此对3个足尺轻钢格栅混凝土组合墙体试件进行了轴压、偏压试验,探究轻钢骨架、水泥纤维板和混凝土的协同工作状态,分析试件的抗压承载力和破坏模式,提出轴压承载力的计算方法。结果表明:相比于无混凝土填充试件,填充混凝土试件的抗压承载力和稳定性均有明显提高;在偏压状态下,试件所受拉力主要由轻钢骨架承担,试件表现出良好的延性特性;增大立柱根数、立柱腹板高度、水泥纤维板厚度以及混凝土强度均可以提高该种组合墙体的抗压承载力,其中对于轴压试件,提高混凝土强度最有效;对于偏压试件,立柱腹板高度、水泥纤维板厚对其抗压承载力影响较大。最后,采用强度叠加方法计算了该种组合墙体轴压承载力,计算结果试验结果吻合良好。

Polarization-Insensitive Silica on Silicon Arrayed Waveguide Grating Design

A new technology for fabrication of silica on silicon arrayed waveguide grating (AWG) based on deep etching and thermal oxidation is presented.Using this method,a silicon layer is remained at the side of waveguide.The stress distribution and effective refractive index of waveguide fabricated by this approach are calculated using finite element and finite difference beam propagation method,respectively.The results of these studies indicate that the stress of silica on silicon optical waveguide can be matched in parallel and vertical direction and AWG polarization dependent wavelength (PDλ) can be reduced effectively due to side-silicon layer.

Modified Holographic Exposure to Fabricate Varied Bragg Grating in an Identical Chip

A new fabricating method is demonstrated to realize two different Bragg gratings in an identical chip using traditional holographic exposure. Polyimide is used to protect one Bragg grating during the first period. The technical process of this method is as simple as that of standard holographic exposure.

Fabrication and Evaluation of Bragg Gratings on Optimally Designed Silicon-on-Insulator Rib Waveguides Using Electron-Beam Lithography

The fabrication of Bragg gratings on silicon-on-insulator （SOI） rib waveguides using electron-beam lithography is presented. The grating waveguide is optimally designed for actual photonic integration. Experimental and theoretical evaluations of the Bragg grating are demonstrated. By thinning the SOl device layer and deeply etching the Bragg grating, a large grating coupling coefficient of 30cm^-1 is obtained.

稀疏线阵宽带波数域反卷积波束形成栅瓣抑制方法

为解决稀疏线列阵的栅瓣与宽带Richardson-Lucy(R-L)反卷积处理生成点扩散函数(PSF)字典计算量大的问题,提出一种宽带波数域的R-L反卷积波束形成栅瓣抑制方法。该方法利用宽带波数域波束形成在波数域的恒束宽特点,使所有频点的反卷积计算共用一个PSF字典,减少反卷积计算的PSF存储空间和计算量;结合在波数域波束形成算法的栅瓣与主瓣之间存在周期平移关系,利用实际波束形成主瓣方位、宽度以及能量对栅瓣进行基于实际数据的宽带栅瓣预测和抑制,可以获得好的抑制效果。通过仿真和海试数据验证了所提方法的性能,结果表明该方法相较于常规宽带反卷积处理可以减少计算量,栅瓣抑制效果大于6 dB,拓展了相同阵元数情况下阵列对宽带目标的探测分辨性能。

Fabrication of arbitrarily apodized fiber Bragg gratings with narrow bandwidth

A double-exposure fabrication method without any intensity shadow mask to fabricate arbitrarily apodized fiber Bragg gratings（ FBGs） with narrow bandwidth is demonstrated by controlling the total ultra violet （UV） irradiation along the grating by varying the speed of a translation stage. The UV source used is a stable continuous intracavity frequency-doubled argonion laser. The parameters （such as length, apodization profile, average index change）of FBGs can be easily changed with this method. The total UV irradiation is kept constant in the doubleexposure process because of the precise control of the exposure time, which ensures that the apodized FBG＇s bandwidth can be extremely narrow. The full width at half maximum （FWHM） bandwidth of the 2-cm-long apodized FBG fabricated by this method is 0. 15 nm with a maximum reflectivity of more than 95%.

光纤光栅传感器在固体发动机药柱内部应变监测中的应用

针对固体发动机药柱结构内部应变响应测量难题,提出了一种基于光纤光栅传感器的内埋式应变测量方法。设计了内埋光纤光栅应变传感器的试验器并对其开展了冷增压试验,获得了试验器药柱内部环向应变与轴向应变值。试验结果表明,提出的测试方法可以获取药柱内部的环向和轴向应变。研究成果可为光纤光栅传感器在固体发动机药柱结构测量中的进一步应用奠定基础,为固体发动机监测技术的发展与应用提供参考。

术中小变温环境下多芯光纤三维位形测量误差研究

为了提高连续体手术机器人术中光纤导航的定位精度,研究了在术中小变温环境下多芯光纤布拉格光栅(FBG)传感器温度补偿方法对提高定位精度的有效性。根据多芯FBG传感器的应变和温度传感模型,仿真分析了小温度变化对形状重构精度的影响。同时建立了术中小变温环境温度补偿实验系统,在4种曲率(0,5.00,6.25,8.30 m^(-1))条件下进行了变温形状重构实验。实验结果表明,在术中小变温环境条件下,温补后的三维位形测量误差从7.70%下降至4.72%,温度补偿能够有效提高多芯光纤形状重构精度,对实现精准定位与导航具有重要的研究意义与应用价值。

Laser Doppler Vibrometer Without Directional Ambiguity Using Rectangular Phase Grating

The two-phase detection method for directional discrimination in laser Doppler measurements is discussed.The diffraction efficiency of a sin- gle period rectangular phase grating is analysed and a kind of back-scattered laser Doppler vibrometer without directional ambiguity using the single peri- od rectangular phase grating as the beam-combiner described.The principles of this kind of vibrometer are explained in detail,and some experimental re- sults are given.In this kind of vibrometer,the rectangular phase grating, without the zero diffracted order and even orders,is used to eliminate use- less stray light and to combine the useful signal light.Differential electronics is employed to reject signal noise.Therefore,the signal-to-noise ratio of Doppler signals and the measurement accuracy of the instrument are im- proved and the range of application is expanded.