We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this pro...We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this process.We find conditions for which the second harmonic generation is highly enhanced even in the absence of phase matching,governed by the exponential growth of the modes residing in the momentum gap of the photonic time crystal.Additionally,under these conditions,a cascade of higher-order harmonics is generated at growing exponential rates.The process is robust,with no requirement for phase-matching,the presence of a resonance or a threshold,drawing energy from the modulation.展开更多
Artificial gauge fields the control over the dynamics of uncharged particles by engineering the potential landscape such that the particles behave as if effective external fields are acting on them.Recent years have w...Artificial gauge fields the control over the dynamics of uncharged particles by engineering the potential landscape such that the particles behave as if effective external fields are acting on them.Recent years have witnessed a growing interest in artificial gauge fields generated either by the geometry or by time-dependent modulation,as they have been enablers of topological phenomena and synthetic dimensions in many physical settings,e.g.,photonics,cold atoms,and acoustic waves.Here,we formulate and experimentally demonstrate the generalized laws of refraction and reflection at an interface between two regions with different artificial gauge fields.We use the symmetries in the system to obtain the generalized Snell law for such a gauge interface and solve for reflection and transmission.We identify total internal reflection(TIR)and complete transmission and demonstrate the concept in experiments.In addition,we calculate the artificial magnetic flux at the interface of two regions with different artificial gauge fields and present a method to concatenate several gauge interfaces.As an example,we propose a scheme to make a gauge imaging system-a device that can reconstruct(image)the shape of an arbitrary wavepacket launched from a certain position to a predesigned location.展开更多
基金supported by the Israel Science Foundation through the MAPATS programby the US Air Force Office for Scientific Research,AFOSR.
文摘We study the nonlinear process of second harmonic generation in photonic time-crystals,materials with refractive index that varies abruptly and periodically in time,and obtain the phase matching condition for this process.We find conditions for which the second harmonic generation is highly enhanced even in the absence of phase matching,governed by the exponential growth of the modes residing in the momentum gap of the photonic time crystal.Additionally,under these conditions,a cascade of higher-order harmonics is generated at growing exponential rates.The process is robust,with no requirement for phase-matching,the presence of a resonance or a threshold,drawing energy from the modulation.
基金support by the Deutsche Forschungsgemeinschaft through CRC/Transregio 185 OSCAR(project No.277625399)support by an ERC Advanced Grant,by the Israel Science Foundationby the German-Israel DIP project.
文摘Artificial gauge fields the control over the dynamics of uncharged particles by engineering the potential landscape such that the particles behave as if effective external fields are acting on them.Recent years have witnessed a growing interest in artificial gauge fields generated either by the geometry or by time-dependent modulation,as they have been enablers of topological phenomena and synthetic dimensions in many physical settings,e.g.,photonics,cold atoms,and acoustic waves.Here,we formulate and experimentally demonstrate the generalized laws of refraction and reflection at an interface between two regions with different artificial gauge fields.We use the symmetries in the system to obtain the generalized Snell law for such a gauge interface and solve for reflection and transmission.We identify total internal reflection(TIR)and complete transmission and demonstrate the concept in experiments.In addition,we calculate the artificial magnetic flux at the interface of two regions with different artificial gauge fields and present a method to concatenate several gauge interfaces.As an example,we propose a scheme to make a gauge imaging system-a device that can reconstruct(image)the shape of an arbitrary wavepacket launched from a certain position to a predesigned location.
