In soft-lattice lead-halide perovskites,the polaronic effects involving stabilization of localized charge character by structural deformations and polarizations have an important effect on the properties of functional...In soft-lattice lead-halide perovskites,the polaronic effects involving stabilization of localized charge character by structural deformations and polarizations have an important effect on the properties of functional materials such as the band gap,which has attracted considerable investigations.However,the concept of polaron assisted nonlinear photonics remains largely unexplored,which has a wide range of applications from optoelectronics to telecommunications and quantum technologies.Here,we report the first observation of the polaronic state assisted saturable absorption through subbandgap excitation with a redshift exceeding 60 meV.By combining photoluminescence,transient absorption measurements and density functional theory calculations,we explicate that the anomalous nonlinear saturable absorption under sub-bandgap excitation is caused by the transient picosecond timescale polaronic state formed by strong carrier/excitonphonon coupling effect.The bandgap fluctuation caused by polaron formation can be further tuned through excitonphonon coupling of perovskites with different Young’s modulus.This suggests that we can design targeted soft lattice lead-halide perovskite with a specific structure to effectively manipulate exciton-phonon coupling and exciton-polaron formation.These findings profoundly expand our understanding of exciton-polaronic nonlinear optics physics and provide an ideal platform for developing actively tunable nonlinear photonics applications.展开更多
The control of polarization,an essential property of light,is of broad scientific and technological interest.Polarizers are indispensable optical elements for direct polarization generation.However,arbitrary polarizat...The control of polarization,an essential property of light,is of broad scientific and technological interest.Polarizers are indispensable optical elements for direct polarization generation.However,arbitrary polarization generation,except that of common linear and circular polarization,relies heavily on bulky optical components such as cascading linear polarizers and waveplates.Here,we present an effective strategy for designing all-in-one full Poincare sphere polarizers based on perfect arbitrary polarization conversion dichroism and implement it in a monolayer all-dielectric metasurface.This strategy allows preferential transmission and conversion of one polarization state located at an arbitrary position on the Poincare sphere to its handedness-flipped state while completely blocking its orthogonal state.In contrast to previous methods that were limited to only linear or circular polarization,our method manifests perfect dichroism of nearly 100%in theory and greater than 90%experimentally for arbitrary polarization states.By leveraging this attractive dichroism,our demonstration of the generation of polarization beams located at an arbitrary position on a Poincare sphere directly from unpolarized light can substantially extend the scope of meta-optics and dramatically promote state-of-the-art nanophotonic devices.展开更多
The emerging meta-holograms rely on arrays of intractable meta-atoms with various geometries and sizes for customized phase profiles that can precisely modulate the phase of a wavefront at an optimal incident angle fo...The emerging meta-holograms rely on arrays of intractable meta-atoms with various geometries and sizes for customized phase profiles that can precisely modulate the phase of a wavefront at an optimal incident angle for given wavelengths.The stringent and band-limited angle tolerance remains a fundamental obstacle for their practical application,in addition to high fabrication precision demands.Utilizing a different design principle,we determined that facile metagrating holograms based on extraordinary optical diffraction can allow the molding of arbitrary wavefronts with extreme angle tolerances(near-grazing incidence)in the visible–near-infrared regime.By modulating the displacements between uniformly sized meta-atoms rather than the geometrical parameters,the metagratings produce a robust detour phase profile that is irrespective of the wavelength or incident angle.The demonstration of high-fidelity meta-holograms and in-site polarization multiplexing significantly simplifies the metasurface design and lowers the fabrication demand,thereby opening new routes for flat optics with high performances and improved practicality.展开更多
Lanthanide-doped upconversion nanoparticles emerged recently as an attractive material platform underpinning a broad range of innovative applications such as optical cryptography,luminescent probes,and lasing.However,...Lanthanide-doped upconversion nanoparticles emerged recently as an attractive material platform underpinning a broad range of innovative applications such as optical cryptography,luminescent probes,and lasing.However,the intricate 4f-associated electronic transition in upconversion nanoparticles leads only to a weak photoluminescence intensity and unpolarized emission,hindering many applications that demand ultrabright and polarized light sources.Here,we present an effective strategy for achieving ultrabright and dual-band polarized upconversion photoluminescence.We employ resonant dielectric metasurfaces supporting high-quality resonant modes at dual upconversion bands enabling two-order-of-magnitude amplification of upconversion emissions.We demonstrate that dual-band resonances can be selectively switched on polarization,endowing cross-polarization controlled upconversion luminescence with ultra-high degrees of polarization,reaching approximately 0.86 and 0.91 at dual emission wavelengths of 540 and 660 nm,respectively.Our strategy offers an effective approach for enhancing photon upconversion processes paving the way towards efficient low-threshold polarization upconversion lasers.展开更多
Bound states in the continuum(BICs)are localized states coexisting with extended waves inside the continuous spectrum range,which have infinite lifetimes without any radiation.To extract high-Q quasi-BIC resonances fr...Bound states in the continuum(BICs)are localized states coexisting with extended waves inside the continuous spectrum range,which have infinite lifetimes without any radiation.To extract high-Q quasi-BIC resonances from the symmetry-protected BIC for practical applications,symmetry-breaking approaches are usually exploited,either by slightly breaking the excitation field symmetry or structure symmetry.Here,we introduce an all-dielectric superlattice metasurface that can symmetrycompatibly convert BIC states into high-Q quasi-BIC modes based on the guidedmode resonance coupling by relative displacement tuning.The metasurface is composed of a superlattice of multiple nanobeams,supporting both magnetic mode and toroidal mode with large tunability.Both modes can interact with the incident continuum by mediating the displacement between nanobeams,which empowers dual asymmetric Fano resonances with high Q-factors.The bandwidth of the toroidal mode under y-polarized incidences and that of the magnetic mode under x-polarized incidences can be readily tuned by the local displacement between nanobeams in each unit cell.Such displacement-mediated BIC resonance is promising for various applications such as bio-molecule sensing and low threshold lasing.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.62275275,11904239,62422506,12474383,52273202)National Key R&D Program of China(2022YFA1604200)+2 种基金Natural Science Foundation of Hunan Province(Grant Nos.2021JJ40709,2022JJ20080,2024JJ6481)Postgraduate Innovative Project of Central South University(Grant No.CX20230246)supported in part by the High-Performance Computing Center of Central South University and Open Sharing Found for the Large-scale Instruments and Equipment of Central South University.
文摘In soft-lattice lead-halide perovskites,the polaronic effects involving stabilization of localized charge character by structural deformations and polarizations have an important effect on the properties of functional materials such as the band gap,which has attracted considerable investigations.However,the concept of polaron assisted nonlinear photonics remains largely unexplored,which has a wide range of applications from optoelectronics to telecommunications and quantum technologies.Here,we report the first observation of the polaronic state assisted saturable absorption through subbandgap excitation with a redshift exceeding 60 meV.By combining photoluminescence,transient absorption measurements and density functional theory calculations,we explicate that the anomalous nonlinear saturable absorption under sub-bandgap excitation is caused by the transient picosecond timescale polaronic state formed by strong carrier/excitonphonon coupling effect.The bandgap fluctuation caused by polaron formation can be further tuned through excitonphonon coupling of perovskites with different Young’s modulus.This suggests that we can design targeted soft lattice lead-halide perovskite with a specific structure to effectively manipulate exciton-phonon coupling and exciton-polaron formation.These findings profoundly expand our understanding of exciton-polaronic nonlinear optics physics and provide an ideal platform for developing actively tunable nonlinear photonics applications.
基金supported by the National Key R&D Program of China(2018YFB1107200)the National Natural Science Foundation of China(NSFC)(Grants 62075084,61522504,61420106014,11734012,and 11574218)+3 种基金the Guangdong Provincial Innovation and Entrepreneurship Project(Grant 2016ZT06D081)the Guangdong Basic and Applied Basic Research Foundation(2020A1515010615)the Fundamental Research Funds for the Central Universities(21620415)the China Scholarship Council(201906785011).
文摘The control of polarization,an essential property of light,is of broad scientific and technological interest.Polarizers are indispensable optical elements for direct polarization generation.However,arbitrary polarization generation,except that of common linear and circular polarization,relies heavily on bulky optical components such as cascading linear polarizers and waveplates.Here,we present an effective strategy for designing all-in-one full Poincare sphere polarizers based on perfect arbitrary polarization conversion dichroism and implement it in a monolayer all-dielectric metasurface.This strategy allows preferential transmission and conversion of one polarization state located at an arbitrary position on the Poincare sphere to its handedness-flipped state while completely blocking its orthogonal state.In contrast to previous methods that were limited to only linear or circular polarization,our method manifests perfect dichroism of nearly 100%in theory and greater than 90%experimentally for arbitrary polarization states.By leveraging this attractive dichroism,our demonstration of the generation of polarization beams located at an arbitrary position on a Poincare sphere directly from unpolarized light can substantially extend the scope of meta-optics and dramatically promote state-of-the-art nanophotonic devices.
基金supported by the National Key R&D Program of China(YS2018YFB110012)the National Natural Science Foundation of China(NSFC)(Grant 11604217,61522504,61420106014,11774145,11734012,11574218)+3 种基金the Fundamental Research Funds for the Central Universities(Grant 21617410)the Guangdong Provincial Innovation and Entrepreneurship Project(Grant 2016ZT06D081,2017ZT07C071)the Applied Science and Technology Project of the Guangdong Science and Technology Department(2017B090918001)the Natural Science Foundation of the Shenzhen Innovation Committee(JCYJ20170412153113701).
文摘The emerging meta-holograms rely on arrays of intractable meta-atoms with various geometries and sizes for customized phase profiles that can precisely modulate the phase of a wavefront at an optimal incident angle for given wavelengths.The stringent and band-limited angle tolerance remains a fundamental obstacle for their practical application,in addition to high fabrication precision demands.Utilizing a different design principle,we determined that facile metagrating holograms based on extraordinary optical diffraction can allow the molding of arbitrary wavefronts with extreme angle tolerances(near-grazing incidence)in the visible–near-infrared regime.By modulating the displacements between uniformly sized meta-atoms rather than the geometrical parameters,the metagratings produce a robust detour phase profile that is irrespective of the wavelength or incident angle.The demonstration of high-fidelity meta-holograms and in-site polarization multiplexing significantly simplifies the metasurface design and lowers the fabrication demand,thereby opening new routes for flat optics with high performances and improved practicality.
基金supporting by national Key R&D Program of China(2021YFB2802003,2022YFB3607300)the China Postdoctoral Science Foundation funded project(No.2022M711241)+1 种基金National Natural Science Foundation of China(NSFC)(62075084)the Guangdong Basic and Applied Basic Research Foundation(2022B1515020004).
文摘Lanthanide-doped upconversion nanoparticles emerged recently as an attractive material platform underpinning a broad range of innovative applications such as optical cryptography,luminescent probes,and lasing.However,the intricate 4f-associated electronic transition in upconversion nanoparticles leads only to a weak photoluminescence intensity and unpolarized emission,hindering many applications that demand ultrabright and polarized light sources.Here,we present an effective strategy for achieving ultrabright and dual-band polarized upconversion photoluminescence.We employ resonant dielectric metasurfaces supporting high-quality resonant modes at dual upconversion bands enabling two-order-of-magnitude amplification of upconversion emissions.We demonstrate that dual-band resonances can be selectively switched on polarization,endowing cross-polarization controlled upconversion luminescence with ultra-high degrees of polarization,reaching approximately 0.86 and 0.91 at dual emission wavelengths of 540 and 660 nm,respectively.Our strategy offers an effective approach for enhancing photon upconversion processes paving the way towards efficient low-threshold polarization upconversion lasers.
基金support provided by the National Key R&D Program of China(2018YFB1107200)Guangdong Basic and Applied Basic Research Foundation(2020A1515010615)+3 种基金the Fundamental Research Funds for the Central Universities(21620415)the National Natural Science Foundation of China(NSFC)(62075084,61522504,61420106014,11734012,and 11574218)Guangzhou Science and Technology Program(202102020566)the Guangdong Provincial Innovation and Entrepreneurship Project(2016ZT06D081).
文摘Bound states in the continuum(BICs)are localized states coexisting with extended waves inside the continuous spectrum range,which have infinite lifetimes without any radiation.To extract high-Q quasi-BIC resonances from the symmetry-protected BIC for practical applications,symmetry-breaking approaches are usually exploited,either by slightly breaking the excitation field symmetry or structure symmetry.Here,we introduce an all-dielectric superlattice metasurface that can symmetrycompatibly convert BIC states into high-Q quasi-BIC modes based on the guidedmode resonance coupling by relative displacement tuning.The metasurface is composed of a superlattice of multiple nanobeams,supporting both magnetic mode and toroidal mode with large tunability.Both modes can interact with the incident continuum by mediating the displacement between nanobeams,which empowers dual asymmetric Fano resonances with high Q-factors.The bandwidth of the toroidal mode under y-polarized incidences and that of the magnetic mode under x-polarized incidences can be readily tuned by the local displacement between nanobeams in each unit cell.Such displacement-mediated BIC resonance is promising for various applications such as bio-molecule sensing and low threshold lasing.
