Tailoring electron vortex beams with customizable intensity patterns by electron diffraction holography

An electron vortex beam(EVB) carrying orbital angular momentum(OAM) plays a key role in a series of fundamental scientific researches, such as chiral energy-loss spectroscopy and magnetic dichroism spectroscopy. So far, almost all the experimentally created EVBs manifest isotropic doughnut intensity patterns. Here, based on the correlation between local divergence angle of electron beam and phase gradient along azimuthal direction, we show that free electrons can be tailored to EVBs with customizable intensity patterns independent of the carried OAM. As proof-of-concept, by using computer generated hologram and designing phase masks to shape the incident free electrons in the transmission electron microscope, three structured EVBs carrying identical OAM are tailored to exhibit completely different intensity patterns. Furthermore, through the modal decomposition, we quantitatively investigate their OAM spectral distributions and reveal that structured EVBs present a superposition of a series of different eigenstates induced by the locally varied geometries. These results not only generalize the concept of EVB, but also demonstrate an extra highly controllable degree of freedom for electron beam manipulation in addition to OAM.

Meta analysis of application of acupuncture combined with drug anesthesia in anorectal surgery

Objective:To evaluate the effectiveness and safety of acupuncture combined drug anesthesia and simple drug anesthesia in anorectal surgery.Methods:The randomized controlled trials of acupuncture combined with drug anesthesia was evaluated using Cochrane systematic review method.The search scope was China National Knowledge Internet,wanfang database,China Biomedical Literature,Pubmed and Embase.The deadline was December 31,2018.The randomized controlled trials of acupuncture combined with anesthesia that met the inclusion criteria were selected.In terms of trial quality evaluation,Cochrane risk bias was used for evaluation.Finally,RevMan 5.2 software was used for statistical analysis.Results:This study finally included 15 articles,a total of 1321 patients.The heterogeneity of significant rate was good,and the combined effect amount OR was 3.55(95%CI[2.06,6.12]).The combined effect quantitative test(Z=4.57,P<0.00001)showed that there was a statistical significance,indicating that acupuncture combined drug anesthesia was better than simple anesthesia in anorectal surgery.The heterogeneity of adverse reactions was good,and the combined effect test(Z=8.88,P<0.00001)showed that there was a statistical significance,indicating that the adverse reaction rate of acupuncture combined with drug anesthesia was lower than that of simple drug anesthesia in the anorectal surgery.Conclusion:Compared with simple drug anesthesia,acupuncture combined with drug anesthesia can improve the anesthesia effect and reduce the occurrence of adverse reactions in anorectal surgery.

Godunov-type solutions for gas-liquid two-phase transient flows with gas release effects

The gas-liquid two-phase homogenous flow has been extensively investigated without the effect of gas release.However,the dissolved gas will release when internal water pressure drops below saturation pressure during hydraulic transients.This results in inaccuracy or even invalidity of the existing model for homogenous flows,especially for the reproduction of two-phase mass transfer processes.To address this problem,this paper couples the gas release model with conservation equations of homogenous flows,which are numerically solved by the second-order Godunov-type scheme(GTS).Specifically,a virtual-cell method is adopted at system boundaries to achieve the same second-order accuracy as interior cells,which is realized by the monotonic upwind scheme for conservation laws(MUSCL-Hancock scheme).Simulated pressure curves by the proposed model are compared with a series of analytical,numerical and experimental results.It indicates that the proposed model with gas release effects reproduces actual pressure responses most accurately,with minimum relative error and root mean squared error compared with experimental data.Moreover,the gas release leads to dynamic synchronous fluctuations of void fraction,wave speed and pressure head,including the opposite trends of void fraction and pressure,and higher void fraction leading to greater wave speed depression.Furthermore,sensitivity analysis is concluded with recommended Courant number,and different gas release effects in different initial void fractions.Present research increases the basic understanding of two-phase mass transfer processes and their implications for hydraulic transients.

Geometric phase-encoded stimuli-responsive cholesteric liquid crystals for visualizing real-time remote monitoring:humidity sensing as a proof of concept

Liquid crystals are a vital component of modern photonics,and recent studies have demonstrated the exceptional sensing properties of stimuli-responsive cholesteric liquid crystals.However,existing cholesteric liquid crystal-based sensors often rely on the naked eye perceptibility of structural color or the measurement of wavelength changes by spectrometric tools,which limits their practical applications.Therefore,developing a platform that produces recognizable sensing signals is critical.In this study,we present a visual sensing platform based on geometric phase encoding of stimuli-responsive cholesteric liquid crystal polymers that generates real-time visual patterns,rather than frequency changes.To demonstrate this platform’s effectiveness,we used a humidity-responsive cholesteric liquid crystal polymer film encoded with a q-plate pattern,which revealed that humidity causes a shape change in the vortex beam reflected from the encoded cholesteric liquid crystal polymers.Moreover,we developed a prototype platform towards remote humidity monitoring benefiting from the high directionality and long-range transmission properties of laser beams carrying orbital angular momentum.Our approach provides a novel sensing platform for cholesteric liquid crystals-based sensors that offers promising practical applications.The ability to generate recognizable sensing signals through visual patterns offers a new level of practicality in the sensing field with stimuli-responsive cholesteric liquid crystals.This platform might have significant implications for a broad readership and will be of interest to researchers working in the field of photonics and sensing technology.

Wearable and interactive multicolored photochromic fiber display

Endowing flexible and adaptable fiber devices with light-emitting capabilities has the potential to revolutionize the current design philosophy of intelligent,wearable interactive devices.However,significant challenges remain in developing fiber devices when it comes to achieving uniform and customizable light effects while utilizing lightweight hardware.Here,we introduce a mass-produced,wearable,and interactive photochromic fiber that provides uniform multicolored light control.We designed independent waveguides inside the fiber to maintain total internal reflection of light as it traverses the fiber.The impact of excessive light leakage on the overall illuminance can be reduced by utilizing the saturable absorption effect of fluorescent materials to ensure light emission uniformity along the transmission direction.In addition,we coupled various fluorescent composite materials inside the fiber to achieve artificially controllable spectral radiation of multiple color systems in a single fiber.We prepared fibers on mass-produced kilometer-long using the thermal drawing method.The fibers can be directly integrated into daily wearable devices or clothing in various patterns and combined with other signal input components to control and display patterns as needed.This work provides a new perspective and inspiration to the existing field of fiber display interaction,paving the way for future human–machine integration.

Broadband tunable liquid crystal terahertz waveplates driven with porous graphene electrodes

Versatile devices,especially tunable ones,for terahertz imaging,sensing and high-speed communication,are in high demand.Liquid crystal based components are perfect candidates in the optical range;however,they encounter significant challenges in the terahertz band,particularly the lack of highly transparent electrodes and the drawbacks induced by a thick cell.Here,a strategy to overcome all these challenges is proposed:Few-layer porous graphene is employed as an electrode with a transmittance of more than 98%.A subwavelength metal wire grid is utilized as an integrated high-efficiency electrode and polarizer.The homogeneous alignment of a high-birefringence liquid crystal is implemented on both frail electrodes via a non-contact photo-alignment technique.A tunable terahertz waveplate is thus obtained.Its polarization evolution is directly demonstrated.Furthermore,quarter-wave plates that are electrically controllable over the entire testing range are achieved by stacking two cells.The proposed solution may pave a simple and bright road toward the development of various liquid crystal terahertz apparatuses.

An all-optical modulator based on a stereo graphene–microfiber structure

An in-line,all-optical fiber modulator based on a stereo graphene–microfiber structure(GMF)utilizing the lab-on-rod technique was demonstrated in this study.Owing to its unique spring-like geometry,an ultra-long GMF interaction can be achieved,and a modulation depth of,7.5 dB(,2.5 dB)and a modulation efficiency of,0.2 dB mW^(-1)(,0.07 dB mW^(-1))were demonstrated for two polarization states.The modulation depth and modulation efficiency are more than one order of magnitude larger than those of other graphene–microfiber hybrid all-optical modulators,although at the cost of a higher insertion loss.By further optimizing the transferring and cleaning process,the upper limit of the modulation depth is mainly determined by the loss from the intrinsic absorption,which depends on the light–graphene interaction.Then,the modulator can quickly switch between the on-state and the off-state with a theoretically maximized modulation depth of tens of decibels.This modulator is compatible with the current fiber-optic communication systems and may be applied in the near future to meet the impending need for ultrafast optical signal processing.

Tunable and enhanced light emission in hybrid WS_(2)-optical-fiber-nanowire structures

In recent years,the two-dimensional(2D)transition metal dichalcogenides(TMDCs)have attracted renewed interest owing to their remarkable physical and chemical properties.Similar to that of graphene,the atomic thickness of TMDCs significantly limits their optoelectronic applications.In this study,we report a hybrid WS_(2)-optical-fibernanowire(WOFN)structure for broadband enhancement of the light-matter interactions,i.e.,light absorption,photoluminescence(PL)and second-harmonic generation(SHG),through evanescent field coupling.The interactions between the anisotropic light field of an optical fiber nanowire(OFN)and the anisotropic second-order susceptibility tensor of WS_(2) are systematically studied theoretically and experimentally.In particular,an efficient SHG in the WOFN appears to be 20 times larger than that in the same OFN before the WS_(2) integration under the same conditions.Moreover,we show that strain can efficiently manipulate the PL and SHG in the WOFN owing to the large configurability of the silica OFN.Our results demonstrate the potential applications of waveguide-coupled TMDCs structures for tunable high-performance photonic devices.

Arbitrary and reconfigurable optical vortex generation:a high-efficiency technique using director-varying liquid crystal fork gratings

A high-efficiency technique for optical vortex(OV) generation is proposed and demonstrated. The technique is based on liquid crystal fork gratings with space-variant azimuthal orientations, which are locally controlled via polarization-sensitive alignment layers. Thanks to the optical rewritability of the alignment agent and the dynamic image generation of the digital micro-mirror device, fork gratings can be instantly and arbitrarily reconfigured.Corresponding optical vortices carrying arbitrary azimuthal and radial indices are demonstrated with a conversion efficiency of 98.5%, exhibiting features of polarization control and electrical switching. The technique may pave a bright road toward OV generation, manipulation, and detection.

Planar liquid crystal polarization optics for near-eye displays

As a promising candidate for next-generation mobile platforms,virtual reality and augmented reality have the potential to revolutionize the way we perceive and interact with various types of digital information.In the meantime,ultrathin planar liquid crystal polarization optics are enabling a new evolutionary trend in near-eye displays.A recent invited review paper published in eLight provides an insightful review on liquid crystal optical elements and their applications toward AR and VR.

Silica optical fiber integrated with two-dimensional materials:towards opto-electro-mechanical technology

In recent years,the integration of graphene and related two-dimensional(2D)materials in optical fbers have stimulated signifcant advances in ll-fber photonics and optoelectronics.The conventional passive silia fiber devices with 2D materials are empowered for enhancing light-matter interactions and are applied for manipulating light beams in respect of their polarization,phase,intensity and frequency,and even realizing the active photo-electric conversion and electro-optic modulation,which paves a new route to the integrated multifunctional ll-fber optoelectronic system.This article reviews the fast-progress field of hybrid 2D-materials-optical fiber for the opto-electro-mechanical devices.The challenges and opportunities in this field for future development are discussed.

All-fiber ultrafast laser generating gigahertz-rate pulses based on a hybrid plasmonic microfiber resonator

Ultrafast lasers generating high-repetition-rate ultrashort pulses through various mode-locking methods can benefit many important applications,including communications,materials processing,astronomical observation,etc.For decades,mode-locking based on dissipative four-wave-mixing(DFWM)has been fundamental in producing pulses with repetition rates on the order of gigahertz(GHz),where multiwavelength comb filters and long nonlinear components are elemental.Recently,this method has been improved using filter-driven DFWM,which exploits both the filtering and nonlinear features of silica microring resonators.However,the fabrication complexity and coupling loss between waveguides and fibers are problematic.We demonstrate a tens-to hundreds-of gigahertz-stable pulsed all-fiber laser based on a hybrid plasmonic microfiber knot resonator device.Unlike previously reported pulse generation mechanisms,the operation utilizes the nonlinear-polarization-rotation(NPR)effect introduced by the polarization-dependent feature of the device to increase intracavity power for boosting DFWM mode-locking,which we term NPRstimulated DFWM.The easily fabricated versatile device acts as a polarizer,comb filter,and nonlinear component simultaneously,thereby introducing an application of microfiber resonator devices in ultrafast and nonlinear photonics.We believe that our work underpins a significant improvement in achieving practical low-cost ultrafast light sources.

Self-assembled liquid crystal architectures for soft matter photonics

Self-assembled architectures of soft matter have fascinated scientists for centuries due to their unique physical properties originated from controllable orientational and/or positional orders,and diverse optic and photonic applications.If one could know how to design,fabricate,and manipulate these optical microstructures in soft matter systems,such as liquid crystals(LCs),that would open new opportunities in both scientific research and practical applications,such as the interaction between light and soft matter,the intrinsic assembly of the topological patterns,and the multidimensional control of the light(polarization,phase,spatial distribution,propagation direction).Here,we summarize recent progresses in self-assembled optical architectures in typical thermotropic LCs and bio-based lyotropic LCs.After briefly introducing the basic definitions and properties of the materials,we present the manipulation schemes of various LC microstructures,especially the topological and topographic configurations.This work further illustrates external-stimuli-enabled dynamic controllability of self-assembled optical structures of these soft materials,and demonstrates several emerging applications.Lastly,we discuss the challenges and opportunities of these materials towards soft matter photonics,and envision future perspectives in this field.

Liquid crystal depolarizer based on photoalignment technology

We propose a depolarizer based on the principle of a collection of half-wave plates with randomly distributed optic axes. The design is demonstrated by means of dynamically photopatterning liquid crystal into randomly aligned homogeneous domains. We characterize the liquid crystal depolarizer for 1550 nm and C-band(1520–1610 nm). A degree of polarization of less than 5% is obtained for any linearly polarized light. This study provides a practical candidate for high-performance depolarizers.

Pancharatnam-Berry phase reversal via opposite-chirality-coexisted superstructures

Recently discovered reflective Pancharatnam-Berry phase(PB phase)from chiral anisotropic media(e.g.,cholesteric liquid crystal,CLC)has aroused great interest in the emerging frontier of planar optics.However,the single chirality of common CLCs results in the intrinsic limitation of the same spin-selective PB phase manipulation,which means the reversal of the input spin cannot realize the conjugated PB phase.In this work,an innovative scheme based on opposite-chirality-coexisted superstructures is proposed to simultaneously modulate orthogonal circular polarization and get PB phase reversal.Through refilling CLC into a washed-out polymer network with opposite chirality and delicate photo-patterned structures,reflective optical vortex(OV)with opposite topological charges and vector beams with conjugated spiral PB phases are efficiently generated depending on the incident polarization.Furthermore,OV holograms are encoded to reconstruct polarization-selective OV arrays,indicating the strong capability of such opposite-chirality-coexisted anisotropic media.This work provides a new compact platform for planar optics,and sheds light on the architectures and functionalities of chiral superstructures.

High-dimensional entanglement generation based on a Pancharatnam–Berry phase metasurface

High-dimensional entanglement is of great importance in quantum communications and can be realized by encoding information on multiple degrees of freedom(Do Fs)of the photons.Conventionally,the realization of such high-dimensional entanglement involves different combinations of bulky optical elements.In this work,we present the use of a single dielectric metasurface to generate high-dimensional entanglement by modulating multi-Do Fs of photons.By sending one of the polarization-entangled photons to interact with the metasurface,we encode path,spin angular momentum,and orbital angular momentum information to the original state.We achieve a four-qubit quantum state in the experiment.To verify it,we experimentally demonstrate the nonlocal correlations between the two photons by recording the correlated images,and we also perform a quantum state tomography measurement.This scheme can be applied to on-chip quantum state manipulation,which is promising in quantum communication with integrated components.

High-fidelity,low-latency polarization quantum state transmissions over a hollow-core conjoined-tube fiber at around 800 nm

Hollow-core fiber(HCF)promises to unify air-borne light propagation and non-line-of-sight transmission,thus holding great potential for versatile photonics-based quantum information applications.The early version of HCF based on photonic-bandgap guidance has not proven itself a reliable quantum channel because of the poor modal purity in both spatial and polarization domains,as well as significant difficulty in fabrication when the wavelength shifts to the visible region.In this work,based on the polarization degree of freedom,we demonstrate high-fidelity(∼0.98)single-photon transmission and distribution of entangled photons over a 36.4 m hollow-core conjoined-tube fiber(CTF)by using commercial silicon single-photon avalanche photodiodes.Our CTF realizes the combined merits of low loss,high spatial modal purity,low polarization degradation,and low chromatic dispersion.We also demonstrate single-photon low-latency(∼99.96%speed of light in vacuum)transmission,paving the way for extensive uses of HCF links in versatile photonics-based quantum information processing.

Going beyond the limit of an LCD’s color gamut

In this study,we analyze how a backlight’s peak wavelength,full-width at half-maximum(FWHM),and color filters affect the color gamut of a liquid crystal display(LCD)device and establish a theoretical limit,even if the FWHM approaches 1 nm.To overcome this limit,we propose a new backlight system incorporating a functional reflective polarizer and a patterned half-wave plate to decouple the polarization states of the blue light and the green/red lights.As a result,the crosstalk between three primary colors is greatly suppressed,and the color gamut is significantly widened.In the experiment,we prepare a white-light source using a blue light-emitting diode(LED)to pump green perovskite polymer film and red quantum dots and demonstrate an exceedingly large color gamut(95.8%Rec.2020 in Commission internationale de l'éclairage(CIE)1931 color space and 97.3%Rec.2020 in CIE 1976 color space)with commercial high-efficiency color filters.These results are beyond the color gamut limit achievable by a conventional LCD.Our design works equally well for other light sources,such as a 2-phosphorconverted white LED.