Observation of the second-harmonic generation(SHG)from subwavelength metallic structures is often hindered by the interrelations of higher-order multipolar contributions.In particular,the magnetic Lorentz contribution...Observation of the second-harmonic generation(SHG)from subwavelength metallic structures is often hindered by the interrelations of higher-order multipolar contributions.In particular,the magnetic Lorentz contribution to SHG is often neglected due to the ineffective magnetic field enhancement in electrically resonant structures.Here,we demonstrate a strong Lorentz-driven SHG output at the plasmon-induced magnetic dipolar resonance in inversionsymmetry-broken plasmonic nanocavities.We observe experimentally tenfold enhancement in the SHG intensity when the magnetic dipole mode is excited,with polarization-resolved measurements confirming the significant role of the hydrodynamic Lorentz-driven second-order nonlinear response.The enhancement originates from a significant spatial overlap between the electric and magnetic fields within the nanometer-scale cavity gaps.Our findings outline the critical role played by the resonant Lorentz-driven optically induced magnetic nonlinearities in metallic nanocavities,and it paves the way towards developing highly efficient nanoscale nonlinear photonic devices.展开更多
Nonlinear Cherenkov radiation(NCR),an intriguing noncollinear second harmonic generation process satisfying versatile longitudinal phase matching and its diffraction in space,has been realized in periodically poled li...Nonlinear Cherenkov radiation(NCR),an intriguing noncollinear second harmonic generation process satisfying versatile longitudinal phase matching and its diffraction in space,has been realized in periodically poled lithium niobate(PPLN)nonlinear grating and other engineered nonlinear photonic structures.Here,we report on the observation of unprecedented ultrabroadband NCR(with a 1.3-octave bandwidth ranging from 363 to 900 nm)from a single PPLN nonlinear grating plate driven by a high-peak-power ultrashort femtosecond pump white laser that covers 2.2-octave bandwidth ranging from 400 to 1,850 nm and possesses a maximum pulse energy of 1.7mJ.Multiple colored NCR patterns along the direction of Cherenkov conical angles simultaneously appear and superimpose in space,leading to a beautifully colorful red-violet rainbow picture dispersed in space clearly observable by the naked eye that has never been reported before.The experiments would enrich the basic physical and optical understanding of nonlinear optical interaction and diffraction characteristics of ultrabroadband high-peak-power white laser sources with engineered nonlinear microstructures.展开更多
基金financial support from the Research Grants Council of Hong Kong through a General Research Fund grant(11305521)supported by the Australian Research Council(Grant No.DP210101292)+3 种基金the International Technology Center Indo-Pacific(ITC IPAC)via Army Research Office(Contract No.FA520923C0023)financial support from the National Natural Science Foundation of China(Grant No.12204328)Sichuan Science and Technology Program(Grant No.2024NSFSC1351)the Fundamental Research Funds for the Central Universities.
文摘Observation of the second-harmonic generation(SHG)from subwavelength metallic structures is often hindered by the interrelations of higher-order multipolar contributions.In particular,the magnetic Lorentz contribution to SHG is often neglected due to the ineffective magnetic field enhancement in electrically resonant structures.Here,we demonstrate a strong Lorentz-driven SHG output at the plasmon-induced magnetic dipolar resonance in inversionsymmetry-broken plasmonic nanocavities.We observe experimentally tenfold enhancement in the SHG intensity when the magnetic dipole mode is excited,with polarization-resolved measurements confirming the significant role of the hydrodynamic Lorentz-driven second-order nonlinear response.The enhancement originates from a significant spatial overlap between the electric and magnetic fields within the nanometer-scale cavity gaps.Our findings outline the critical role played by the resonant Lorentz-driven optically induced magnetic nonlinearities in metallic nanocavities,and it paves the way towards developing highly efficient nanoscale nonlinear photonic devices.
基金supported by the Science and Technology Project of Guangdong(2020B010190001)the National Natural Science Foundation of China(12434016)+1 种基金the National Key R&D Program of China(2023YFA1406900)the National Funded Postdoctoral Researcher Program(GZB20240785).
文摘Nonlinear Cherenkov radiation(NCR),an intriguing noncollinear second harmonic generation process satisfying versatile longitudinal phase matching and its diffraction in space,has been realized in periodically poled lithium niobate(PPLN)nonlinear grating and other engineered nonlinear photonic structures.Here,we report on the observation of unprecedented ultrabroadband NCR(with a 1.3-octave bandwidth ranging from 363 to 900 nm)from a single PPLN nonlinear grating plate driven by a high-peak-power ultrashort femtosecond pump white laser that covers 2.2-octave bandwidth ranging from 400 to 1,850 nm and possesses a maximum pulse energy of 1.7mJ.Multiple colored NCR patterns along the direction of Cherenkov conical angles simultaneously appear and superimpose in space,leading to a beautifully colorful red-violet rainbow picture dispersed in space clearly observable by the naked eye that has never been reported before.The experiments would enrich the basic physical and optical understanding of nonlinear optical interaction and diffraction characteristics of ultrabroadband high-peak-power white laser sources with engineered nonlinear microstructures.
