Modification of Longitudinal Modulus of 3D Full Five Directional Braided Composite Materials Base on Energy Theory

The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its topological structure. Then, according to the intrinsic relation of different cells, the axial moduli of internal, surface and corner cells are systematically deduced, and the influence of corner-cell periodic discontinuity on the moduli is also analyzed. Finally, considering the actual shape of axial yarns after consolidation, the longitudinal moduli of the different cells are modified based on energy theory. The technology factor λ is also proposed in this modification. The results show that the axial mechanical properties of this material can be strongly designable. The straightness of the axial yarns greatly affects the longitudinal modulus. Technology factor λ is between 1 to 2, corresponding to the minimum and the maximum modulus, respectively.

Side Polished Fiber:A Versatile Platform for Compact Fiber Devices and Sensors

Side polished fiber(SPF)has a controllable average roughness and length of the side-polishing region,which becomes a versatile platform for integrating multiple materials to interact with the evanescent field to fabricate all-fiber devices and sensors.It has been widely used in couplers,filters,polarizers,optical attenuators,photodetectors,modulators,and sensors for temperature,humidity,strain,biological molecules,chemical gas,and vector magnetic monitoring.In this article,an overview of the development history,fabrication techniques,fiber types,transmission characteristics,and varied recent applications of SPFs are reviewed.Firstly,the fabrication techniques of SPFs are reviewed,including the V-groove assisted polishing technique and wheel polishing technique.Then,the different types of SPFs and their characteristics are discussed.Finally,various applications of SPFs are discussed and concluded theoretically and experimentally,including their principles and structures.When designing the device,the residual thickness and polishing lengths of the SPF need to be appropriately selected in order to obtain the best performance.Developing all-fiber devices and sensors is aimed at practical usability under harsh environments and allows to avoid the high coupling loss between optical fibers and on-chip integrated devices.

High-sensitivity and fast-response fiber optic temperature sensor using an anti-resonant reflecting optical waveguide mechanism

Temperature sensing is essential for human health monitoring.High-sensitivity(>1 nm∕℃)fiber sensors always require long interference paths and temperature-sensitive materials,leading to a long sensor and thus slow response(6–14 s).To date,it is still challenging for a fiber optic temperature sensor to have an ultrafast(~ms)response simultaneously with high sensitivity.Here,a side-polished single-mode/hollow/single-mode fiber(SPSHSF)structure is proposed to meet the challenge by using the length-independent sensitivity of an anti-resonant reflecting optical waveguide mechanism.With a polydimethylsiloxane filled sub-nanoliter volume cavity in the SP-SHSF,the SP-SHSF exhibits a high temperature sensitivity of 4.223 nm/℃ with a compact length of 1.6 mm,allowing an ultrafast response(16 ms)and fast recovery time(176 ms).The figure of merit(FOM),defined as the absolute ratio of sensitivity to response time,is proposed to assess the comprehensive performance of the sensor.The FOM of the proposed sensor reaches up to 263.94(nm/℃)∕s,which is more than two to three orders of magnitude higher than those of other temperature fiber optic sensors reported previously.Additionally,a threemonth cycle test shows that the sensor is highly robust,with excellent reversibility and accuracy,allowing it to be incorporated with a wearable face mask for detecting temperature changes during human breathing.The high FOM and high stability of the proposed sensing fiber structure provide an excellent opportunity to develop both ultrafast and highly sensitive fiber optic sensors for wearable respiratory monitoring and contactless in vitro detection.

Sensitivity-enhanced surface plasmon resonance sensor utilizing a tungsten disulfide (WS_2) nanosheets overlayer

Tungsten disulfide(WS_2), as a representative layered transition metal dichalcogenide(TMDC) material, possesses important potential for applications in highly sensitive sensors. Here, a sensitivity-enhanced surface plasmon resonance(SPR) sensor with a metal film modified by an overlayer of WS_2 nanosheets is proposed and demonstrated. The SPR sensitivity is related to the thickness of the WS_2 overlayer, which can be tailored by coating a WS_2 ethanol suspension with different concentrations or by the number of times of repeated post-coating.Benefitting from its large surface area, high refractive index, and unique optoelectronic properties, the WS_2 nanosheet overlayer coated on the gold film significantly improves the sensing sensitivity. The highest sensitivity(up to 2459.3 nm∕RIU) in the experiment is achieved by coating the WS_2 suspension once. Compared to the case without a WS_2 overlayer, this result shows a sensitivity enhancement of 26.6%. The influence of the WS_2 nanosheet overlayer on the sensing performance improvement is analyzed and discussed. Moreover, the proposed WS_2 SPR sensor has a linear correlation coefficient of 99.76% in refractive index range of 1.333 to 1.360. Besides sensitivity enhancement, the WS_2 nanosheet overlayer is able to show additional advantages, such as protection of metal film from oxidation, tunability of the resonance wavelength region, biocompatibility, capability of vapor,and gas sensing.

Photonic cavity enhanced high-performance surface plasmon resonance biosensor

Herein we propose a novel strategy to enhance surface plasmon resonance(SPR)by introducing a photonic cavity into a total-internal-reflection architecture.The photonic cavity,which is comprised of a highly reflective photonic crystal(PC),defect layers,and a gold(Au)film,enables Fabry–Perot(FP)resonances in the defect layers and therefore narrows the SPR resonance width in the metallic surface as well as increases the electric field intensity and penetration depth in the evanescent region.The fabricated sensor exhibits a 5.7-fold increase in the figure of merit and a higher linear coefficient as compared with the conventional Au-SPR sensor.The demonstrated PC/FP cavity/metal structure presents a new design philosophy for SPR performance enhancement.

High-performance fiber-integrated multifunctional graphene-optoelectronic device with photoelectric detection and optic-phase modulation

In graphene-based optoelectronic devices,the ultraweak interaction between a light and monolayer graphene leads to low optical absorption and low responsivity for the photodetectors and relative high half-wave voltage for the phase modulator.Here,an integration of the monolayer graphene onto the side-polished optical fiber is demonstrated,which is capable of providing a cost-effective strategy to enhance the light–graphene interaction,allowing us to obtain a highly efficient optical absorption in graphene and achieve multifunctions:photodetection and optical phase modulation.As a photodetector,the device has ultrahigh responsivity(1.5×10^(7) A/W)and high external quantum efficiency(>1.2×10^(9)%).Additionally,the polybutadiene/polymethyl methacrylate(PMMA)film on the graphene can render the device an optical phase modulator through the large thermo-optic effect of the PMMA.As a phase modulator,the device has a relatively low half-wave voltage of 3 V with a 16 dB extinction ratio in Mach–Zehnder interferometer configuration.

Optimized weak measurement of orbital angular momentum-induced beam shifts in optical reflection

Tiny but universal beam shifts occur when a polarized light beam is reflected upon a planar interface.Although the beam shifts of Gaussian beams have been measured by the weak measurement technique, the weak measurement for orbital angular momentum(OAM)-induced spatial shifts of vortex beams is still missing.Here, by elaborately choosing the preselection and postselection states, the tiny OAM-induced Goos–H?nchen and Imbert–Fedorov shifts are amplified at an air–prism interface. The maximum shifts along directions both parallel and perpendicular to the incident plane are theoretically predicted and experimentally verified with optimal preselection and postselection states. These maximum shifts can be used to determine the OAM of vortex beams.

Tunable spin splitting of Laguerre–Gaussian beams in graphene metamaterials

Optical spin splitting has attracted significant attention owing to its potential applications in quantum information and precision metrology. However, it is typically small and cannot be controlled efficiently. Here, we enhance the spin splitting by transmitting higher-order Laguerre–Gaussian(LG) beams through graphene metamaterial slabs. The interaction between LG beams and metamaterial results in an orbital-angularmomentum-(OAM) dependent spin splitting. The upper bound of the OAM-dependent spin splitting is found,which varies with the incident OAM and beam waist. Moreover, the spin splitting can be flexibly tuned by modulating the Fermi energy of the graphene sheets. This tunable spin splitting has potential applications in the development of spin-based applications and the manipulation of mid-infrared waves.

Distance-controllable and direction-steerable opto-conveyor for targeting delivery

Opto-conveyors have attracted widespread interest in various fields because of their non-invasive and non-contact delivery of micro/nanoparticles.However,the flexible control of the delivery distance and the dynamic steering of the delivery direction,although very desirable in all-optical manipulation,have not yet been achieved by optoconveyors.Here,using a simple and cost-effective scheme of an elliptically focused laser beam obliquely irradiated on a substrate,a direction-steerable and distance-controllable opto-conveyor for the targeting delivery of microparticles is implemented.Theoretically,in the proposed scheme of the opto-conveyor,the transverse and longitudinal resultant forces of the optical gradient force and the optical scattering force result in the transverse confinement and the longitudinal transportation of microparticles,respectively.In this study,it is experimentally shown that the proposed opto-conveyor is capable of realizing the targeting delivery for microparticles.Additionally,the delivery distance of microparticles can be flexibly and precisely controlled by simply adjusting the irradiation time.By simply rotating the cylindrical lens,the proposed opto-conveyor is capable of steering the delivery direction flexibly within a large range of azimuthal angles,from-75°to 75°.This study also successfully demonstrated the real-time dynamic steering of the delivery direction from-45°to 45°with the dynamical rotation of the cylindrical lens.Owing to its simplicity,flexibility,and controllability,the proposed method is capable of creating new opportunities in bioassays as well as in drug delivery.

Resonance-assisted light–control–light characteristics of SnS_2 on a microfiber knot resonator with fast response

An all-optical light–control–light functionality with the structure of a microfiber knot resonator (MKR) coated with tin disulfide (SnS_2) nanosheets is experimentally demonstrated. The evanescent light in the MKR [with a resonance Q of ～59,000 and an extinction ratio (ER) of ～26 dB] is exploited to enhance light–matter interaction by coating a two-dimensional material SnS_2 nanosheet onto it. Thanks to the enhanced light–matter interaction and the strong absorption property of SnS_2, the transmitted optical power can be tuned quasi-linearly with an external violet pump light power, where a transmitted optical power variation rate ΔT with respect to the violet light power of ～0.22 dB∕mW is obtained. In addition, the MKR structure possessing multiple resonances enables a direct experimental demonstration of the relationship between resonance properties (such as Q and ER), and the obtained ΔT variation rate with respect to the violet light power. It verifies experimentally that a higher resonance Q and a larger ER can lead to a higher ΔT variation rate. In terms of the operating speed, this device runs as fast as ～3.2 ms. This kind of all-optical light–control–light functional structure may find applications in future all-optical circuitry, handheld fiber sensors, etc.