Chirality plays an important role in biological processes,and enantiomers often possess similar physical properties and different physiologic functions.In recent years,chiral detection of enantiomers become a popular ...Chirality plays an important role in biological processes,and enantiomers often possess similar physical properties and different physiologic functions.In recent years,chiral detection of enantiomers become a popular topic.Plasmonic metasurfaces enhance weak inherent chiral effects of biomolecules,so they are used in chiral detection.Artificial intelligence algorithm makes a lot of contribution to many aspects of nanophotonics.Here,we propose a nanostructure design method based on reinforcement learning and devise chiral nanostructures to distinguish enantiomers.The algorithm finds out the metallic nanostructures with a sharp peak in circular dichroism spectra and emphasizes the frequency shifts caused by nearfield interaction of nanostructures and biomolecules.Our work inspires universal and efficient machine-learning methods for nanophotonic design.展开更多
Phonon-assisted photon upconversion(UPC)is an anti-Stokes process in which incident photons achieve higher energy emission by absorbing phonons.This letter studies phonon-assisted UPC in twisted 2D semiconductors,in w...Phonon-assisted photon upconversion(UPC)is an anti-Stokes process in which incident photons achieve higher energy emission by absorbing phonons.This letter studies phonon-assisted UPC in twisted 2D semiconductors,in which an inverted contrast between UPC and conventional photoluminescence(PL)of WSe2 twisted bilayer is emergent.A 4-fold UPC enhancement is achieved in 5.5°twisted bilayer while PL weakens by half.Reduced interlayer exciton conversion efficiency driven by lattice relaxation,along with enhanced pump efficiency resulting from spectral redshift,lead to the rotation-angle-dependent UPC enhancement.The counterintuitive phenomenon provides a novel insight into a unique way that twisted angle affects UPC and light-matter interactions in 2D semiconductors.Furthermore,the UPC enhancement platform with various superimposable means offers an effective method for lighting bilayers and expanding the application prospect of 2D stacked van der Waals devices.展开更多
The manipulation of polarization states beyond the optical limit presents advantages in various applications.Considerable progress has been made in the design of meta-waveplates for on-demand polarization transformati...The manipulation of polarization states beyond the optical limit presents advantages in various applications.Considerable progress has been made in the design of meta-waveplates for on-demand polarization transformation,realized by numerical simulations and parameter sweep methodologies.However,due to the limited freedom in these classical strategies,particular challenges arise from the emerging requirement for multiplex optical devices and multidimensional manipulation of light,which urge for a large number of different nanostructures with great polarization control capability.Here,we demonstrate a set of self-designed arbitrary wave plates with a high polarization conversion efficiency.We combine Bayesian optimization and deep neural networks to design perfect halfand quarter-waveplates based on metallic nanostructures,which experimentally demonstrate excellent polarization control functionalities with the conversion ratios of 85%and 90%.More broadly,we develop a comprehensive wave plate database consisting of various metallic nanostructures with high polarization conversion efficiency,accompanying a flexible tuning of phase shifts(0-2π)and group delays(0-10 fs),and construct an achromatic metalens based on this database.Owing to the versatility and excellent performance,our self-designed wave plates can promote the performance of multiplexed broadband metasurfaces and find potential applications in compact optical devices and polarization division multiplexing optical communications.展开更多
Phonon-assisted upconverted emission is the heart of energy harvesting,bioimaging,optical cryptography,and optical refrigeration.It has been demonstrated that emerging two-dimensional(2D)semiconductors can provide an ...Phonon-assisted upconverted emission is the heart of energy harvesting,bioimaging,optical cryptography,and optical refrigeration.It has been demonstrated that emerging two-dimensional(2D)semiconductors can provide an excellent platform for efficient phonon-assisted upconversion due to the enhanced optical transition strength and phonon-exciton interaction of 2D excitons.However,there is little research on the further enhancement of excitonic upconverted emission in 2D semiconductors.Here,we report the enhanced multiphoton upconverted emission of 2D excitons in doubly resonant plasmonic nanocavities.Owing to the enhanced light collection,enhanced excitation rate,and quantum efficiency enhancement arising from the Purcell effect,an upconverted emission amplification of>1000-fold and a decrease of 2~3 orders of magnitude in the saturated excitation power are achieved.These findings pave the way for the development of excitonic upconversion lasing,nanoscopic thermometry,and sensing,revealing the possibility of optical refrigeration in future 2D electronic or excitonic devices.展开更多
基金This work is supported by the National Science Foundation of China(Grant Nos.12027807,62225501,and 11974002)National Key Research and Development Program of China(Grant No.2020YFA0211300,2020YFA0906900,and 2021YFF1200500)PKU-Baidu Fund Project(Grant No.2020BD023),and High-performance Computing Platform of Peking University.
文摘Chirality plays an important role in biological processes,and enantiomers often possess similar physical properties and different physiologic functions.In recent years,chiral detection of enantiomers become a popular topic.Plasmonic metasurfaces enhance weak inherent chiral effects of biomolecules,so they are used in chiral detection.Artificial intelligence algorithm makes a lot of contribution to many aspects of nanophotonics.Here,we propose a nanostructure design method based on reinforcement learning and devise chiral nanostructures to distinguish enantiomers.The algorithm finds out the metallic nanostructures with a sharp peak in circular dichroism spectra and emphasizes the frequency shifts caused by nearfield interaction of nanostructures and biomolecules.Our work inspires universal and efficient machine-learning methods for nanophotonic design.
基金supports from the National Key Research and Development Program of China(2020YFA0211300)National Science Foundation of China(grant Nos.62225501,12027807)+1 种基金Bejing Natural Science Foundation(grant Nos.Z180011)High-performance Computing Platform of Peking University.
文摘Phonon-assisted photon upconversion(UPC)is an anti-Stokes process in which incident photons achieve higher energy emission by absorbing phonons.This letter studies phonon-assisted UPC in twisted 2D semiconductors,in which an inverted contrast between UPC and conventional photoluminescence(PL)of WSe2 twisted bilayer is emergent.A 4-fold UPC enhancement is achieved in 5.5°twisted bilayer while PL weakens by half.Reduced interlayer exciton conversion efficiency driven by lattice relaxation,along with enhanced pump efficiency resulting from spectral redshift,lead to the rotation-angle-dependent UPC enhancement.The counterintuitive phenomenon provides a novel insight into a unique way that twisted angle affects UPC and light-matter interactions in 2D semiconductors.Furthermore,the UPC enhancement platform with various superimposable means offers an effective method for lighting bilayers and expanding the application prospect of 2D stacked van der Waals devices.
基金National Key Research and Development Program of China(2020YFA0211300)National Natural Science Foundation of China(12027807,62225501)+1 种基金PKU-Baidu Fund Project(2020BD023)High-performance Computing Platform of Peking University。
文摘The manipulation of polarization states beyond the optical limit presents advantages in various applications.Considerable progress has been made in the design of meta-waveplates for on-demand polarization transformation,realized by numerical simulations and parameter sweep methodologies.However,due to the limited freedom in these classical strategies,particular challenges arise from the emerging requirement for multiplex optical devices and multidimensional manipulation of light,which urge for a large number of different nanostructures with great polarization control capability.Here,we demonstrate a set of self-designed arbitrary wave plates with a high polarization conversion efficiency.We combine Bayesian optimization and deep neural networks to design perfect halfand quarter-waveplates based on metallic nanostructures,which experimentally demonstrate excellent polarization control functionalities with the conversion ratios of 85%and 90%.More broadly,we develop a comprehensive wave plate database consisting of various metallic nanostructures with high polarization conversion efficiency,accompanying a flexible tuning of phase shifts(0-2π)and group delays(0-10 fs),and construct an achromatic metalens based on this database.Owing to the versatility and excellent performance,our self-designed wave plates can promote the performance of multiplexed broadband metasurfaces and find potential applications in compact optical devices and polarization division multiplexing optical communications.
基金supported by National Key Research and Development Program of China(grant no.2017YFA0206000)Beijing Natural Science Foundation(grant nos.Z180011)+2 种基金National Key Research Program(2017YFA0205700,2019YFA0210203,2020YFA0211300)National Science Foundation of China(gant nos.12027807,21790364,12104241)High-performance Computing Platform of Peking University.
文摘Phonon-assisted upconverted emission is the heart of energy harvesting,bioimaging,optical cryptography,and optical refrigeration.It has been demonstrated that emerging two-dimensional(2D)semiconductors can provide an excellent platform for efficient phonon-assisted upconversion due to the enhanced optical transition strength and phonon-exciton interaction of 2D excitons.However,there is little research on the further enhancement of excitonic upconverted emission in 2D semiconductors.Here,we report the enhanced multiphoton upconverted emission of 2D excitons in doubly resonant plasmonic nanocavities.Owing to the enhanced light collection,enhanced excitation rate,and quantum efficiency enhancement arising from the Purcell effect,an upconverted emission amplification of>1000-fold and a decrease of 2~3 orders of magnitude in the saturated excitation power are achieved.These findings pave the way for the development of excitonic upconversion lasing,nanoscopic thermometry,and sensing,revealing the possibility of optical refrigeration in future 2D electronic or excitonic devices.