Collective cell migration is a coordinated movement of multi-cell systems essential for various processes throughout life.The collective motions often occur under spatial restrictions,hallmarked by the collective rota...Collective cell migration is a coordinated movement of multi-cell systems essential for various processes throughout life.The collective motions often occur under spatial restrictions,hallmarked by the collective rotation of epithelial cells confined in circular substrates.Here,we aim to explore how geometric shapes of confinement regulate this collective cell movement.We develop quantitative methods for cell velocity orientation analysis,and find that boundary cells exhibit stronger tangential ordering migration than inner cells in circular pattern.Furthermore,decreased tangential ordering movement capability of collective cells in triangular and square patterns are observed,due to the disturbance of cell motion at unsmooth corners of these patterns.On the other hand,the collective cell rotation is slightly affected by a convex defect of the circular pattern,while almost hindered with a concave defect,also resulting from different smoothness features of their boundaries.Numerical simulations employing cell Potts model well reproduce and extend experimental observations.Together,our results highlight the importance of boundary smoothness in the regulation of collective cell tangential ordering migration.展开更多
Holographic display has attracted widespread interest because of its ability to show the complete information of the object and bring people an unprecedented sense of presence. The absence of ideal recording materials...Holographic display has attracted widespread interest because of its ability to show the complete information of the object and bring people an unprecedented sense of presence. The absence of ideal recording materials has hampered the realization of their commercial applications. Here we report that the response time of a bismuth and magnesium codoped lithium niobate(LN:Bi,Mg) crystal is shortened to 7.2 ms and a sensitivity as high as 646 cm/J. The crystal was used to demonstrate a real-time holographic display with a refresh rate of 60 Hz, as that of the popular high-definition television. Moreover, the first-principles calculations indicate that the electron mobility while Bi occupying Nb-site is significantly greater than that in Li-site, which directly induces the fast response of LN:Bi,Mg crystals when the concentration of Mg is above its doping threshold.展开更多
Actin cytoskeleton plays crucial roles in various cellular functions.Extracellular matrix(ECM)can modulate cell morphology by remodeling the internal cytoskeleton.To define how geometry of ECM regulates the organizati...Actin cytoskeleton plays crucial roles in various cellular functions.Extracellular matrix(ECM)can modulate cell morphology by remodeling the internal cytoskeleton.To define how geometry of ECM regulates the organization of actin cytoskeleton,we plated individual NIH 3T3 cells on micropatterned substrates with distinct shapes and sizes.It was found that the stress fibers could form along the nonadhesive edges of T-shaped pattern,but were absent from the opening edge of V-shaped pattern,indicating that the organization of actin cytoskeleton was dependent on the mechanical environment.Furthermore,a secondary actin ring was observed on 50μm circular pattern while did not appear on 30μm and 40μm pattern,showing a size-dependent organization of actin cytoskeleton.Finally,osteoblasts,MDCK and A549 cells exhibited distinct organization of actin cytoskeleton on T-shaped pattern,suggesting a cell-type specificity in arrangement of actin cytoskeleton.Together,our findings brought novel insight into the organization of actin cytoskeleton on micropatterned environments.展开更多
As the indispensable oxygen-transporting cells,erythrocytes exhibit extreme deformability and amazing stability as they are subject to huge reversible shear stress and extrusion force during massive circulation in the...As the indispensable oxygen-transporting cells,erythrocytes exhibit extreme deformability and amazing stability as they are subject to huge reversible shear stress and extrusion force during massive circulation in the body.The unique architecture of spectrin-actin-based membraneskeleton is considered to be responsible for such excellent mechanical properties of erythrocytes.Although erythrocytes have been recognized for more than 300 years,myriad questions about membrane-skeleton constantly attract people's attention.Here,we summarize the kinds of distinctive single-cell and single-molecule techniques that were used to investigate the structure and function of erythrocyte membrane-skeleton at macro and micro levels.展开更多
Synthetic dimensions(SDs)opened the door for exploring previously inaccessible phenomena in high-dimensional space.However,construction of synthetic lattices with desired coupling properties is a challenging and unint...Synthetic dimensions(SDs)opened the door for exploring previously inaccessible phenomena in high-dimensional space.However,construction of synthetic lattices with desired coupling properties is a challenging and unintuitive task.Here,we use deep learning artificial neural networks(ANNs)to construct lattices in real space with a predesigned spectrum of mode eigenvalues,and thus to validly design the dynamics in synthetic mode dimensions.By employing judiciously chosen perturbations(wiggling of waveguides at desired frequencies),we show resonant mode coupling and tailored dynamics in SDs.Two distinct examples are illustrated:one features uniform synthetic mode coupling,and the other showcases the edge defects that allow for tailored light transport and confinement.Furthermore,we demonstrate morphing of light into a topologically protected edge mode with modified Su-Schrieffer-Heeger photonic lattices.Such an ANN-assisted construction of SDs may advance toward“utopian networks,”opening new avenues for fundamental research beyond geometric limitations as well as for applications in mode lasing,optical switching,and communication technologies.展开更多
The oxidation behavior and kinetics of Ti_(2)AlC-20vol.%TiB_(2) composite at 600-900℃ in air were investigated.The results showed that the oxidation kinetics of the composite followed a logarithmic law within the giv...The oxidation behavior and kinetics of Ti_(2)AlC-20vol.%TiB_(2) composite at 600-900℃ in air were investigated.The results showed that the oxidation kinetics of the composite followed a logarithmic law within the given temperature range,which indicated that the composites had excellent oxidation resistance.The selective oxidation of Al in Ti_(2)AlC was greatly enhanced,which facilitated the formation of a continuous and dense protective layer of Al_(2)O_(3).Meanwhile,the existence of molten B_(2)O_(3) inhibited the outward diffusion of Ti and inward diffusion of oxygen,which prevented the growth of anatase TiO_(2) at 600℃ and rutile TiO_(2) at 700-900℃.Therefore,the incorporation of TiB_(2) completely inhibited the abnormally rapid oxidation of bulk Ti_(2)AlC at 600℃ and improved its oxidation resistance at 700-900℃.展开更多
Lithium niobate thin film frequency doubler has extensive applications in the preparation of classical and quantum sources.In this study,we successfully fabricated microdisk resonators with a quality factor of 2.2...Lithium niobate thin film frequency doubler has extensive applications in the preparation of classical and quantum sources.In this study,we successfully fabricated microdisk resonators with a quality factor of 2.2×10^(5) in reverse-polarization dual-layer x-cut lithium niobate for the first time.Based on the modal phase matching condition,efficient second harmonic generation with a record normalized conversion efficiency of~56000%W-1 and cascaded third harmonic generation with an efficiency of~6500%W-2 were obtained in the microdisk resonator.Compared with the periodically poled lithium niobate microcavity,the complex domain structure preparation processes are avoided.Our work provides a scheme for achieving highly efficient second-order nonlinear effects in non-periodically poled microcavities.展开更多
Optical Kerr effect, in which input light intensity linearly alters the refractive index, has enabled the generation ofoptical solitons, supercontinuum spectra, and frequency combs, playing vital roles in the on-chip ...Optical Kerr effect, in which input light intensity linearly alters the refractive index, has enabled the generation ofoptical solitons, supercontinuum spectra, and frequency combs, playing vital roles in the on-chip devices, fibercommunications, and quantum manipulations. Especially, terahertz Kerr effect, featuring fascinating prospects in futurehigh-rate computing, artificial intelligence, and cloud-based technologies, encounters a great challenge due to therather low power density and feeble Kerr response. Here, we demonstrate a giant terahertz frequency Kerr nonlinearitymediated by stimulated phonon polaritons. Under the influences of the giant Kerr nonlinearity, the power-dependentrefractive index change would result in a frequency shift in the microcavity, which was experimentally demonstratedvia the measurement of the resonant mode of a chip-scale lithium niobate Fabry-Pérot microcavity. Attributed to theexistence of stimulated phonon polaritons, the nonlinear coefficient extracted from the frequency shifts is orders ofmagnitude larger than that of visible and infrared light, which is also theoretically demonstrated by nonlinear Huangequations. This work opens an avenue for many rich and fruitful terahertz Kerr effect based physical, chemical, andbiological systems that have terahertz fingerprints.展开更多
Crystalline lithium niobate(LN)is an important optical material because of its broad transmission window that spans from ultraviolet to mid-infrared and its large nonlinear and electro-optic coefficients.Furthermore,t...Crystalline lithium niobate(LN)is an important optical material because of its broad transmission window that spans from ultraviolet to mid-infrared and its large nonlinear and electro-optic coefficients.Furthermore,the recent development and commercialization of LN-on-insulator(LNOI)technology has opened an avenue for the realization of integrated on-chip photonic devices with unprecedented performances in terms of propagation loss,optical nonlinearity,and electro-optic tunability.This review begins with a brief introduction of the history and current status of LNOI photonics.We then discuss the fabrication techniques of LNOI-based photonic structures and devices.The recent revolution in the LN photonic industry has been sparked and is still being powered by innovations of the nanofabrication technology of LNOI,which enables the production of building block structures,such as optical microresonators and waveguides of unprecedented optical qualities.The following sections present various on-chip LNOI devices categorized into nonlinear photonic and electro-optic tunable devices and photonic-integrated circuits.Some conclusions and future perspectives are provided.展开更多
Lithium niobate(LN)thin film has received much attention as an integrated photonic platform,due to its rich and great photoelectric characteristics,based on which various functional photonic devices,such as electro-op...Lithium niobate(LN)thin film has received much attention as an integrated photonic platform,due to its rich and great photoelectric characteristics,based on which various functional photonic devices,such as electro-optic modulators and nonlinear wavelength converters,have been demonstrated with impressive performance.As an important part of the integrated photonic system,the long-awaited laser and amplifier on the LN thin-film platform have made a series of breakthroughs and important progress recently.In this review paper,the research progress of lasers and amplifiers realized on lithium niobate thin film platforms is reviewed comprehensively.Specifically,the research progress on optically pumped lasers and amplifiers based on rare-earth ions doping of LN thin films is introduced.Some important parameters and existing limitations of the current development are discussed.In addition,the implementation scheme and research progress of electrically pumped lasers and amplifiers on LN thin-film platforms are summarized.The advantages and disadvantages of optically and electrically pumped LN thin film light sources are analyzed.Finally,the applications of LN thin film lasers and amplifiers and other on-chip functional devices are envisaged.展开更多
Microcavity lasers based on erbium-doped lithium niobate on insulator(LNOI),which are key devices for LNOI integrated photonics,have attracted significant attention recently.In this study,we report the realization of ...Microcavity lasers based on erbium-doped lithium niobate on insulator(LNOI),which are key devices for LNOI integrated photonics,have attracted significant attention recently.In this study,we report the realization of a C-band single-mode laser using the Vernier effect in two coupled erbium-doped LNOI microrings with different radii under the pump of a 980-nm continuous laser.The laser,operating stably over a large range of pumping power,has a pump threshold of about 200μW and a side-mode suppression ratio exceeding 26 dB.The high-performance LNOI single-mode laser will promote the development of lithium niobate integrated photonics.展开更多
Lithium niobate on insulator(LNOI) provides a platform for the fundamental physics investigations and practical applications of integrated photonics. However, as an indispensable building block of integrated photonics...Lithium niobate on insulator(LNOI) provides a platform for the fundamental physics investigations and practical applications of integrated photonics. However, as an indispensable building block of integrated photonics, lasers are in short supply. In this paper, erbium-doped LNOI laser in the 1550-nm band was demonstrated in microdisk cavities with high quality factors fabricated in batches by UV exposure, inductively coupled plasma reactive ion etching, and chemomechanical polishing. The threshold and conversion efficiency of the erbium-doped LNOI microdisk laser were measured to be lower than 1 m W and 6.5×10^(-5)%, respectively. This work will benefit the development of integrated photonics based on LNOI.展开更多
Lithium niobate on insulator(LNOI), as an emerging and promising optical integration platform, faces shortages of on-chip active devices including lasers and amplifiers. Here, we report the fabrication of on-chip erbi...Lithium niobate on insulator(LNOI), as an emerging and promising optical integration platform, faces shortages of on-chip active devices including lasers and amplifiers. Here, we report the fabrication of on-chip erbium-doped LNOI waveguide amplifiers based on electron beam lithography and inductively coupled plasma reactive ion etching. A net internal gain of ~30 d B/cm in the communication band was achieved in the fabricated waveguide amplifiers under the pump of a974 nm continuous laser. This work develops new active devices on LNOI and may promote the development of LNOI integrated photonics.展开更多
In this study, we investigate the fabrication of periodically poled lithium niobate(PPLN) microdisk cavities on a chip. These resonators are fabricated from a PPLN film with a 16 μm poling period on insulator using c...In this study, we investigate the fabrication of periodically poled lithium niobate(PPLN) microdisk cavities on a chip. These resonators are fabricated from a PPLN film with a 16 μm poling period on insulator using conventional microfabrication techniques.The quality factor of the PPLN microdisk resonators with a 40-μm radius and a 700-nm thickness is 6.7×10~5. Second harmonic generation(SHG) with an efficiency of 2.2×10^(-6) mW(-1) is demonstrated in the fabricated PPLN microdisks. The nonlinear conversion efficiency could be considerably enhanced by optimizing the period and pattern of the poled structure and by improving the cavity quality factors.展开更多
Many applications of metasurfaces require an ability to dynamically change their properties in the time domain. Electrical tuning techniques are of particular interest, since they pave a way to on-chip integration of ...Many applications of metasurfaces require an ability to dynamically change their properties in the time domain. Electrical tuning techniques are of particular interest, since they pave a way to on-chip integration of metasurfaces with optoelectronic devices.In this work, we propose and experimentally demonstrate an electro-optic lithium niobate(EO-LN) metasurface that shows dynamic modulations to phase retardation of transmitted light. Quasi-bound states in the continuum(QBIC) are observed from this metasurface. By applying external electric voltages, the refractive index of lithium niobate(LN) is changed by Pockels EO nonlinearity, leading to efficient phase modulations to the transmitted light around the QBIC wavelength. The EO-LN metasurface developed in this study opens up new routes for potential applications in the field of displaying, pulse shaping, and spatial light modulating.展开更多
The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals....The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals.Despite tremendous efforts in engineering synthetic cold-atom,as well as electronic and photonic lattices to explore orbital physics,thus far high orbitals in an important class of materials,namely,higher-order topological insulators(HOTIs),have not been realized.Here,we demonstrate p-orbital corner states in a photonic HOTI,unveiling their underlying topological invariant,symmetry protection,and nonlinearity-induced dynamical rotation.In a Kagome-type HOTI,we find that the topological protection of p-orbital corner states demands an orbital-hopping symmetry in addition to generalized chiral symmetry.Due to orbital hybridization,nontrivial topology of the p-orbital HOTI is“hidden”if bulk polarization is used as the topological invariant,but well manifested by the generalized winding number.Our work opens a pathway for the exploration of intriguing orbital phenomena mediated by higher-band topology applicable to a broad spectrum of systems.展开更多
Higher-order topological insulators(HOTIs)are recently discovered topological phases,possessing symmetry-protected corner states with fractional charges.An unexpected connection between these states and the seemingly ...Higher-order topological insulators(HOTIs)are recently discovered topological phases,possessing symmetry-protected corner states with fractional charges.An unexpected connection between these states and the seemingly unrelated phenomenon of bound states in the continuum(BICs)was recently unveiled.When nonlinearity is added to the HOTI system,a number of fundamentally important questions arise.For example,how does nonlinearity couple higher-order topological BICs with the rest of the system,including continuum states?In fact,thus far BICs in nonlinear HOTIs have remained unexplored.Here we unveil the interplay of nonlinearity,higher-order topology,and BICs in a photonic platform.We observe topological corner states that are also BICs in a laser-written second-order topological lattice and further demonstrate their nonlinear coupling with edge(but not bulk)modes under the proper action of both self-focusing and defocusing nonlinearities.Theoretically,we calculate the eigenvalue spectrum and analog of the Zak phase in the nonlinear regime,illustrating that a topological BIC can be actively tuned by nonlinearity in such a photonic HOTI.Our studies are applicable to other nonlinear HOTI systems,with promising applications in emerging topology-driven devices.展开更多
A fabrication process allowing for the production of periodically poled lithium niobate(PPLN)photonic devices with any domain pattern and unit size down to 200 nm is developed by combining semiconductor fabrication te...A fabrication process allowing for the production of periodically poled lithium niobate(PPLN)photonic devices with any domain pattern and unit size down to 200 nm is developed by combining semiconductor fabrication techniques and piezo-force-microscopy tips polarization.Based on this fabrication process,PPLN microdisk resonators with quality factors of 8×10~4 were fabricated from a Z-cut lithium niobate film.Second-harmonic generation(SHG)utilizing d(33)in the whole cavity was demonstrated in a PPLN microdisk with a 2μm-spatialperiod radial domain pattern.The SHG conversion efficiency was measured to be 1.44×10^(-5)m W^(-1).This work paves the way to fabricate complex PPLN photonic devices and to obtain efficient nonlinear optical effects that have wide applications in both classical and quantum optics.展开更多
The flourishing of topological photonics in the last decade was achieved mainly due to developments in linear topological photonic structures.However,when nonlinearity is introduced,many intriguing questions arise.For...The flourishing of topological photonics in the last decade was achieved mainly due to developments in linear topological photonic structures.However,when nonlinearity is introduced,many intriguing questions arise.For example,are there universal fingerprints of the underlying topology when modes are coupled by nonlinearity,and what can happen to topological invariants during nonlinear propagation?To explore these questions,we experimentally demonstrate nonlinearity-induced coupling of light into topologically protected edge states using a photonic platform and develop a general theoretical framework for interpreting the mode-coupling dynamics in nonlinear topological systems.Performed on laser-written photonic Su-Schrieffer-Heeger lattices,our experiments show the nonlinear coupling of light into a nontrivial edge or interface defect channel that is otherwise not permissible due to topological protection.Our theory explains all the observations well.Furthermore,we introduce the concepts of inherited and emergent nonlinear topological phenomena as well as a protocol capable of revealing the interplay of nonlinearity and topology.These concepts are applicable to other nonlinear topological systems,both in higher dimensions and beyond our photonic platform.展开更多
We report the first observation, to the best of our knowledge, of sum-frequency generation in on-chip lithium niobate microdisk resonators. The sum-frequency signal in the 780 nm band, distinct in wavelength from seco...We report the first observation, to the best of our knowledge, of sum-frequency generation in on-chip lithium niobate microdisk resonators. The sum-frequency signal in the 780 nm band, distinct in wavelength from secondharmonic signals, was obtained in lithium niobate microresonators under the pump of two individual 1550 nm band lasers. The sum-frequency conversion efficiency was measured to be 1.4 × 10^(-7) mW^(-1). The dependence of the intensities of the nonlinear signals on the total pump power and the wavelength of one pump laser was investigated while fixing the wavelength of the other. This work paves the way for applications of on-chip lithium niobate microdisk resonators ranging from infrared single-photon detection to infrared spectroscopy.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12174208 and 32227802)National Key Research and Development Program of China(No.2022YFC3400600)+2 种基金Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030009)Fundamental Research Funds for the Central Universities(Nos.2122021337 and 2122021405)the 111 Project(No.B23045).
文摘Collective cell migration is a coordinated movement of multi-cell systems essential for various processes throughout life.The collective motions often occur under spatial restrictions,hallmarked by the collective rotation of epithelial cells confined in circular substrates.Here,we aim to explore how geometric shapes of confinement regulate this collective cell movement.We develop quantitative methods for cell velocity orientation analysis,and find that boundary cells exhibit stronger tangential ordering migration than inner cells in circular pattern.Furthermore,decreased tangential ordering movement capability of collective cells in triangular and square patterns are observed,due to the disturbance of cell motion at unsmooth corners of these patterns.On the other hand,the collective cell rotation is slightly affected by a convex defect of the circular pattern,while almost hindered with a concave defect,also resulting from different smoothness features of their boundaries.Numerical simulations employing cell Potts model well reproduce and extend experimental observations.Together,our results highlight the importance of boundary smoothness in the regulation of collective cell tangential ordering migration.
基金The National Key Research and Development Program of China(Grant No.2019YFA0705000)National Natural Science Foundation of China(No.12034010)Program for Changjiang Scholars and Innovative Research Team in University(No.IRT_13R29).
文摘Holographic display has attracted widespread interest because of its ability to show the complete information of the object and bring people an unprecedented sense of presence. The absence of ideal recording materials has hampered the realization of their commercial applications. Here we report that the response time of a bismuth and magnesium codoped lithium niobate(LN:Bi,Mg) crystal is shortened to 7.2 ms and a sensitivity as high as 646 cm/J. The crystal was used to demonstrate a real-time holographic display with a refresh rate of 60 Hz, as that of the popular high-definition television. Moreover, the first-principles calculations indicate that the electron mobility while Bi occupying Nb-site is significantly greater than that in Li-site, which directly induces the fast response of LN:Bi,Mg crystals when the concentration of Mg is above its doping threshold.
基金This work was supported by the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030009)the National Key Research and Development Program of China(2022YFC3400600)National Natural Science Foundation of China(12174208,32227802,11874231,31801134 and 31870843)+2 种基金Tianjin Natural Science Foundation(20JCYBJC01010)China Postdoctoral Science Foundation(2020M680032)Fundamental Research Funds for the Central Universities(2122021337 and 2122021405).
文摘Actin cytoskeleton plays crucial roles in various cellular functions.Extracellular matrix(ECM)can modulate cell morphology by remodeling the internal cytoskeleton.To define how geometry of ECM regulates the organization of actin cytoskeleton,we plated individual NIH 3T3 cells on micropatterned substrates with distinct shapes and sizes.It was found that the stress fibers could form along the nonadhesive edges of T-shaped pattern,but were absent from the opening edge of V-shaped pattern,indicating that the organization of actin cytoskeleton was dependent on the mechanical environment.Furthermore,a secondary actin ring was observed on 50μm circular pattern while did not appear on 30μm and 40μm pattern,showing a size-dependent organization of actin cytoskeleton.Finally,osteoblasts,MDCK and A549 cells exhibited distinct organization of actin cytoskeleton on T-shaped pattern,suggesting a cell-type specificity in arrangement of actin cytoskeleton.Together,our findings brought novel insight into the organization of actin cytoskeleton on micropatterned environments.
基金the National Natural Science Foundation of China(Nos.11874231,11574165 and 31801134)Tianjin Natural Science Foundation(No.18JCQNJC02000)+1 种基金the PCSIRT(No.IRT 13R29)the 111 Project(No.B07013).
文摘As the indispensable oxygen-transporting cells,erythrocytes exhibit extreme deformability and amazing stability as they are subject to huge reversible shear stress and extrusion force during massive circulation in the body.The unique architecture of spectrin-actin-based membraneskeleton is considered to be responsible for such excellent mechanical properties of erythrocytes.Although erythrocytes have been recognized for more than 300 years,myriad questions about membrane-skeleton constantly attract people's attention.Here,we summarize the kinds of distinctive single-cell and single-molecule techniques that were used to investigate the structure and function of erythrocyte membrane-skeleton at macro and micro levels.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1404800)the National Natural Science Foundation of China(Grant Nos.12134006,12274242,11922408,and 12204252)+7 种基金the China Postdoctoral Science Foundation(Grant Nos.BX2021134 and 2021M701790)the Natural Science Foundation of Tianjin for Distinguished Young Scholars(Grant No.21JCJQJC00050)PCSIRT(Grant No.IRT_13R29)the 111 Project(Grant No.B23045)in Chinasupport from the Croatian-Chinese bilateral project funded by the Ministry of Science and Education in Croatia and the Ministry of Science and Technology in Chinasupport from the project“Implementation of cutting-edge research and its application as part of the Scientific Center of Excellence for Quantum and Complex Systems,and Representations of Lie Algebras,”European UnionEuropean Regional Development Fundsupport from the Canada Research Chair program and from NSERC via the Discovery Grant program
文摘Synthetic dimensions(SDs)opened the door for exploring previously inaccessible phenomena in high-dimensional space.However,construction of synthetic lattices with desired coupling properties is a challenging and unintuitive task.Here,we use deep learning artificial neural networks(ANNs)to construct lattices in real space with a predesigned spectrum of mode eigenvalues,and thus to validly design the dynamics in synthetic mode dimensions.By employing judiciously chosen perturbations(wiggling of waveguides at desired frequencies),we show resonant mode coupling and tailored dynamics in SDs.Two distinct examples are illustrated:one features uniform synthetic mode coupling,and the other showcases the edge defects that allow for tailored light transport and confinement.Furthermore,we demonstrate morphing of light into a topologically protected edge mode with modified Su-Schrieffer-Heeger photonic lattices.Such an ANN-assisted construction of SDs may advance toward“utopian networks,”opening new avenues for fundamental research beyond geometric limitations as well as for applications in mode lasing,optical switching,and communication technologies.
基金supported by the National Natural Science Foundation of China(Grant No.52071318).
文摘The oxidation behavior and kinetics of Ti_(2)AlC-20vol.%TiB_(2) composite at 600-900℃ in air were investigated.The results showed that the oxidation kinetics of the composite followed a logarithmic law within the given temperature range,which indicated that the composites had excellent oxidation resistance.The selective oxidation of Al in Ti_(2)AlC was greatly enhanced,which facilitated the formation of a continuous and dense protective layer of Al_(2)O_(3).Meanwhile,the existence of molten B_(2)O_(3) inhibited the outward diffusion of Ti and inward diffusion of oxygen,which prevented the growth of anatase TiO_(2) at 600℃ and rutile TiO_(2) at 700-900℃.Therefore,the incorporation of TiB_(2) completely inhibited the abnormally rapid oxidation of bulk Ti_(2)AlC at 600℃ and improved its oxidation resistance at 700-900℃.
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0705000)the National Natural Science Foundation of China(Grant Nos.12034010,12134007,11734009,92050111,12074199,92050114,and 12004197)the 111 Project(Grant No.B23045)。
文摘Lithium niobate thin film frequency doubler has extensive applications in the preparation of classical and quantum sources.In this study,we successfully fabricated microdisk resonators with a quality factor of 2.2×10^(5) in reverse-polarization dual-layer x-cut lithium niobate for the first time.Based on the modal phase matching condition,efficient second harmonic generation with a record normalized conversion efficiency of~56000%W-1 and cascaded third harmonic generation with an efficiency of~6500%W-2 were obtained in the microdisk resonator.Compared with the periodically poled lithium niobate microcavity,the complex domain structure preparation processes are avoided.Our work provides a scheme for achieving highly efficient second-order nonlinear effects in non-periodically poled microcavities.
基金supported by the National Natural Science Foundation of China(62205158 and 11974192)the Foundation of State Key Laboratory of laser Interaction with Matter(SKLLIM2101)the 111 Project(B23045).
文摘Optical Kerr effect, in which input light intensity linearly alters the refractive index, has enabled the generation ofoptical solitons, supercontinuum spectra, and frequency combs, playing vital roles in the on-chip devices, fibercommunications, and quantum manipulations. Especially, terahertz Kerr effect, featuring fascinating prospects in futurehigh-rate computing, artificial intelligence, and cloud-based technologies, encounters a great challenge due to therather low power density and feeble Kerr response. Here, we demonstrate a giant terahertz frequency Kerr nonlinearitymediated by stimulated phonon polaritons. Under the influences of the giant Kerr nonlinearity, the power-dependentrefractive index change would result in a frequency shift in the microcavity, which was experimentally demonstratedvia the measurement of the resonant mode of a chip-scale lithium niobate Fabry-Pérot microcavity. Attributed to theexistence of stimulated phonon polaritons, the nonlinear coefficient extracted from the frequency shifts is orders ofmagnitude larger than that of visible and infrared light, which is also theoretically demonstrated by nonlinear Huangequations. This work opens an avenue for many rich and fruitful terahertz Kerr effect based physical, chemical, andbiological systems that have terahertz fingerprints.
基金Natural Basic Research Program of China(2019YFA0705000)National Natural Science Foundation of China(11674181,11674340,11734009,11822410,11874154,11874375,61590934,61761136006)+5 种基金Key Research Program of Frontier Sciences(QYZDJ-SSWSLH010)Key Project of the Shanghai Science and Technology Committee(17JC1400400,18DZ1112700)Strategic Priority Research Program of Chinese Academy of Sciences(XDB16030300)Higher Education Discipline Innovation Project(B07013)Program for Changjiang Scholars and Innovative Research Team(IRT_13R29)State Key Laboratory of Advanced Optical Communication Systems and Networks(2019GZKF03006).
文摘Crystalline lithium niobate(LN)is an important optical material because of its broad transmission window that spans from ultraviolet to mid-infrared and its large nonlinear and electro-optic coefficients.Furthermore,the recent development and commercialization of LN-on-insulator(LNOI)technology has opened an avenue for the realization of integrated on-chip photonic devices with unprecedented performances in terms of propagation loss,optical nonlinearity,and electro-optic tunability.This review begins with a brief introduction of the history and current status of LNOI photonics.We then discuss the fabrication techniques of LNOI-based photonic structures and devices.The recent revolution in the LN photonic industry has been sparked and is still being powered by innovations of the nanofabrication technology of LNOI,which enables the production of building block structures,such as optical microresonators and waveguides of unprecedented optical qualities.The following sections present various on-chip LNOI devices categorized into nonlinear photonic and electro-optic tunable devices and photonic-integrated circuits.Some conclusions and future perspectives are provided.
基金This work was financially supported by the National Key Research and Development Program of China(Grant No.2019YFA0705000)National Natural Science Foundation of China(Grant Nos.92250302,12034010,12134007,92050111,12074199,92050114,and 12004197)the 111 Project(Grant No.B23045).
文摘Lithium niobate(LN)thin film has received much attention as an integrated photonic platform,due to its rich and great photoelectric characteristics,based on which various functional photonic devices,such as electro-optic modulators and nonlinear wavelength converters,have been demonstrated with impressive performance.As an important part of the integrated photonic system,the long-awaited laser and amplifier on the LN thin-film platform have made a series of breakthroughs and important progress recently.In this review paper,the research progress of lasers and amplifiers realized on lithium niobate thin film platforms is reviewed comprehensively.Specifically,the research progress on optically pumped lasers and amplifiers based on rare-earth ions doping of LN thin films is introduced.Some important parameters and existing limitations of the current development are discussed.In addition,the implementation scheme and research progress of electrically pumped lasers and amplifiers on LN thin-film platforms are summarized.The advantages and disadvantages of optically and electrically pumped LN thin film light sources are analyzed.Finally,the applications of LN thin film lasers and amplifiers and other on-chip functional devices are envisaged.
基金the National Key Research and Development Program of China(Grant No.2019YFA0705000)the National Natural Science Foundation of China(Grant Nos.12034010,11734009,92050111,12074199,92050114,12004197,and 1774182)the 111 Project(Grant No.B07013).
文摘Microcavity lasers based on erbium-doped lithium niobate on insulator(LNOI),which are key devices for LNOI integrated photonics,have attracted significant attention recently.In this study,we report the realization of a C-band single-mode laser using the Vernier effect in two coupled erbium-doped LNOI microrings with different radii under the pump of a 980-nm continuous laser.The laser,operating stably over a large range of pumping power,has a pump threshold of about 200μW and a side-mode suppression ratio exceeding 26 dB.The high-performance LNOI single-mode laser will promote the development of lithium niobate integrated photonics.
基金supported by the National Key Research and Development Program of China (Grant No. 2019YFA0705000)the National Natural Science Foundation of China (Grant Nos. 12034010, 11734009, 11674181,11674184, and 11774182)+2 种基金the Higher Education Discipline Innovation Project (Grant No. B07013)the National Science Fund for Talent Training in the Basic Sciences (Grant No. J1103208)the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT)(Grant No. IRT_13R29)。
文摘Lithium niobate on insulator(LNOI) provides a platform for the fundamental physics investigations and practical applications of integrated photonics. However, as an indispensable building block of integrated photonics, lasers are in short supply. In this paper, erbium-doped LNOI laser in the 1550-nm band was demonstrated in microdisk cavities with high quality factors fabricated in batches by UV exposure, inductively coupled plasma reactive ion etching, and chemomechanical polishing. The threshold and conversion efficiency of the erbium-doped LNOI microdisk laser were measured to be lower than 1 m W and 6.5×10^(-5)%, respectively. This work will benefit the development of integrated photonics based on LNOI.
基金supported by the National Key Research and Development Program of China(No.2019YFA0705000)the National Natural Science Foundation of China(Nos.12034010,11734009,92050111,92050114,12074199,12004197,and 11774182)+1 种基金the Higher Education Discipline Innovation Project(No.B07013)the Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)(No.IRT_13R29)。
文摘Lithium niobate on insulator(LNOI), as an emerging and promising optical integration platform, faces shortages of on-chip active devices including lasers and amplifiers. Here, we report the fabrication of on-chip erbium-doped LNOI waveguide amplifiers based on electron beam lithography and inductively coupled plasma reactive ion etching. A net internal gain of ~30 d B/cm in the communication band was achieved in the fabricated waveguide amplifiers under the pump of a974 nm continuous laser. This work develops new active devices on LNOI and may promote the development of LNOI integrated photonics.
基金supported by the National Natural Science Foundation of China(Grant Nos.11734009,11674181,11774182,and 11674184)the 111 Project(Grant No.B07013)+1 种基金PCSIRT(Grant No.IRT 13R29)CAS Interdisciplinary Innovation Team
文摘In this study, we investigate the fabrication of periodically poled lithium niobate(PPLN) microdisk cavities on a chip. These resonators are fabricated from a PPLN film with a 16 μm poling period on insulator using conventional microfabrication techniques.The quality factor of the PPLN microdisk resonators with a 40-μm radius and a 700-nm thickness is 6.7×10~5. Second harmonic generation(SHG) with an efficiency of 2.2×10^(-6) mW(-1) is demonstrated in the fabricated PPLN microdisks. The nonlinear conversion efficiency could be considerably enhanced by optimizing the period and pattern of the poled structure and by improving the cavity quality factors.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research (Grant No.2020B0301030009)the National Key R&D Program of China (Grant Nos.2017YFA0305100,2017YFA0303800,and 2019YFA0705000)+5 种基金the National Natural Science Foundation of China (Grant Nos.92050114,91750204,61775106,11904182,12074200,and 11774185)the 111 Project (Grant No.B07013)PCSIRT (Grant No.IRT0149)the Open Research Program of Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang ProvinceFundamental Research Funds for the Central Universities (Grant Nos.010-63201003,01063201008,and 010-63201009)Tianjin Youth Talent Support Program。
文摘Many applications of metasurfaces require an ability to dynamically change their properties in the time domain. Electrical tuning techniques are of particular interest, since they pave a way to on-chip integration of metasurfaces with optoelectronic devices.In this work, we propose and experimentally demonstrate an electro-optic lithium niobate(EO-LN) metasurface that shows dynamic modulations to phase retardation of transmitted light. Quasi-bound states in the continuum(QBIC) are observed from this metasurface. By applying external electric voltages, the refractive index of lithium niobate(LN) is changed by Pockels EO nonlinearity, leading to efficient phase modulations to the transmitted light around the QBIC wavelength. The EO-LN metasurface developed in this study opens up new routes for potential applications in the field of displaying, pulse shaping, and spatial light modulating.
基金the National Key R&D Program of China(2022YFA1404800)the National Natural Science Foundation of China(12134006,12274242)+4 种基金the Natural Science Foundation of Tianjin(21JCJQJC00050)the QuantiXLie Center of Excellence,a project co-financed by the Croatian Government and the European Union through the European Regional Development Fund the Competitiveness and Cohesion Operational Programme(KK.01.1.1.01.0004)the 66 Postdoctoral Science Grant of Chinathe NSERC Discovery Grantthe Canada Research Chair Programs.
文摘The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals.Despite tremendous efforts in engineering synthetic cold-atom,as well as electronic and photonic lattices to explore orbital physics,thus far high orbitals in an important class of materials,namely,higher-order topological insulators(HOTIs),have not been realized.Here,we demonstrate p-orbital corner states in a photonic HOTI,unveiling their underlying topological invariant,symmetry protection,and nonlinearity-induced dynamical rotation.In a Kagome-type HOTI,we find that the topological protection of p-orbital corner states demands an orbital-hopping symmetry in addition to generalized chiral symmetry.Due to orbital hybridization,nontrivial topology of the p-orbital HOTI is“hidden”if bulk polarization is used as the topological invariant,but well manifested by the generalized winding number.Our work opens a pathway for the exploration of intriguing orbital phenomena mediated by higher-band topology applicable to a broad spectrum of systems.
基金This research is supported by the National Key R&D Program of China under Grant No.2017YFA0303800the National Natural Science Foundation(11922408,91750204,11674180)+2 种基金PCSIRT,and the 111 Project(No.B07013)in ChinaD.B.acknowledges support from the 66 Postdoctoral Science Grant of ChinaD.J.and H.B.acknowledge support in part by the Croatian Science Foundation Grant No.IP-2016-06-5885 SynthMagIA and the QuantiXLie Center of Excellence,a project co-financed by the Croatian Government and European Union through the European Regional Development Fund-the Competitiveness and Cohesion Operational Programme(Grant KK.01.1.1.01.0004)。
文摘Higher-order topological insulators(HOTIs)are recently discovered topological phases,possessing symmetry-protected corner states with fractional charges.An unexpected connection between these states and the seemingly unrelated phenomenon of bound states in the continuum(BICs)was recently unveiled.When nonlinearity is added to the HOTI system,a number of fundamentally important questions arise.For example,how does nonlinearity couple higher-order topological BICs with the rest of the system,including continuum states?In fact,thus far BICs in nonlinear HOTIs have remained unexplored.Here we unveil the interplay of nonlinearity,higher-order topology,and BICs in a photonic platform.We observe topological corner states that are also BICs in a laser-written second-order topological lattice and further demonstrate their nonlinear coupling with edge(but not bulk)modes under the proper action of both self-focusing and defocusing nonlinearities.Theoretically,we calculate the eigenvalue spectrum and analog of the Zak phase in the nonlinear regime,illustrating that a topological BIC can be actively tuned by nonlinearity in such a photonic HOTI.Our studies are applicable to other nonlinear HOTI systems,with promising applications in emerging topology-driven devices.
基金National Key Research and Development Program of China(2019YFA0705000)National Natural Science Foundation of China(11674181,11674184,11734009,11774182)+2 种基金Higher Education Discipline Innovation Project(B07013)National Science Fund for Talent Training in the Basic Sciences(J1103208)PCSIRT(IRT13R29)。
文摘A fabrication process allowing for the production of periodically poled lithium niobate(PPLN)photonic devices with any domain pattern and unit size down to 200 nm is developed by combining semiconductor fabrication techniques and piezo-force-microscopy tips polarization.Based on this fabrication process,PPLN microdisk resonators with quality factors of 8×10~4 were fabricated from a Z-cut lithium niobate film.Second-harmonic generation(SHG)utilizing d(33)in the whole cavity was demonstrated in a PPLN microdisk with a 2μm-spatialperiod radial domain pattern.The SHG conversion efficiency was measured to be 1.44×10^(-5)m W^(-1).This work paves the way to fabricate complex PPLN photonic devices and to obtain efficient nonlinear optical effects that have wide applications in both classical and quantum optics.
基金supported by the National Key R&D Program of China under Grant No.2017YFA0303800the National Natural Science Foundation(11922408,91750204,11674180),PCSIRT+5 种基金the 111 Project(No.B07013)in Chinasupport in part by the Croatian Science Foundation Grant No.IP-2016-06-5885 SynthMagIAthe QuantiXLie Center of Excellence,a project co-financed by the Croatian Government and European Union through the European Regional Development Fund-the Competitiveness and Cohesion Operational Programme(Grant KK.01.1.1.01.0004)supported by the Australian Research Council(DE19010043)supported by the Institute for Basic Science in Korea(IBS-R024-Y1)support from the Russian Foundation for Basic Research(grant No.19-52-12053).
文摘The flourishing of topological photonics in the last decade was achieved mainly due to developments in linear topological photonic structures.However,when nonlinearity is introduced,many intriguing questions arise.For example,are there universal fingerprints of the underlying topology when modes are coupled by nonlinearity,and what can happen to topological invariants during nonlinear propagation?To explore these questions,we experimentally demonstrate nonlinearity-induced coupling of light into topologically protected edge states using a photonic platform and develop a general theoretical framework for interpreting the mode-coupling dynamics in nonlinear topological systems.Performed on laser-written photonic Su-Schrieffer-Heeger lattices,our experiments show the nonlinear coupling of light into a nontrivial edge or interface defect channel that is otherwise not permissible due to topological protection.Our theory explains all the observations well.Furthermore,we introduce the concepts of inherited and emergent nonlinear topological phenomena as well as a protocol capable of revealing the interplay of nonlinearity and topology.These concepts are applicable to other nonlinear topological systems,both in higher dimensions and beyond our photonic platform.
基金National Natural Science Foundation of China(NSFC)(11374165,11674181,11674184,61475077)Ministry of Science and Technology of the People’s Republic of China(MOST)(2013CB328702)+1 种基金Ministry of Education of the People’s Republic of China(MOE)(B07013)PCSIRT(IRT_13R29)
文摘We report the first observation, to the best of our knowledge, of sum-frequency generation in on-chip lithium niobate microdisk resonators. The sum-frequency signal in the 780 nm band, distinct in wavelength from secondharmonic signals, was obtained in lithium niobate microresonators under the pump of two individual 1550 nm band lasers. The sum-frequency conversion efficiency was measured to be 1.4 × 10^(-7) mW^(-1). The dependence of the intensities of the nonlinear signals on the total pump power and the wavelength of one pump laser was investigated while fixing the wavelength of the other. This work paves the way for applications of on-chip lithium niobate microdisk resonators ranging from infrared single-photon detection to infrared spectroscopy.
