Non-radiative optical modes attracted enormous attention in optics due to strong light confinement and giant Q-factor at its spectral position.The destructive interference of multipoles leads to zero net-radiation and...Non-radiative optical modes attracted enormous attention in optics due to strong light confinement and giant Q-factor at its spectral position.The destructive interference of multipoles leads to zero net-radiation and strong field trapping.Such radiationless states disappear in the far-field,localize enhanced near-field and can be excited in nanostructures.On the other hand,the optical modes turn out to be completely confined due to no losses at discrete point in the radiation continuum,such states result in infinite Q-factor and lifetime.The radiationless states provide a suitable platform for enhanced light matter interaction,lasing,and boost nonlinear processes at the state regime.These modes are widely investigated in different material configurations for various applications in both linear and nonlinear metasurfaces which are briefly discussed in this review.展开更多
Weyl points,which are the degenerate points in three-dimensional momentum space,have been widely studied in the photonic system,and show some intriguing phenomena such as topologically protected surface states and chi...Weyl points,which are the degenerate points in three-dimensional momentum space,have been widely studied in the photonic system,and show some intriguing phenomena such as topologically protected surface states and chiral anomalies.Type-I Weyl systems possess a complete bandgap,and topologically protected surface states can be excited without disturbing the bulk states.In this work,we investigate the influence of the sign of coupling coefficient on the topological property of the system and find that type-I Weyl points can be realized by introducing a negative coupling between the stacking layers of the designed photonic crystal.We propose a new strategy to construct a type-I Weyl system by stacking the hexagonal photonic lattice.Different from the topological nontrivial photonic system with a positive coefficient,the negative couplings in the photonic system are realized by adding another resonating site between stacking layers.We theoretically demonstrate that the effective coupling between the resonating sites in adjacent layers sign-flips through the judicious design of the nearest coupling strength and eigenfrequency of the additional sites.The surface states at opposite boundaries of the proposed system have opposite group velocities,which is the feature of type-I Weyl points.Our study provides a new method of exploring topologically protected photonic systems and developing possible topological devices.展开更多
基金the funding provided by the Beijing Outstanding Young Scientist Program(BJJWZYJH01201910007022)Science and Technology Innovation Program of Beijing Institute of Technology(2021CX01008).
文摘Non-radiative optical modes attracted enormous attention in optics due to strong light confinement and giant Q-factor at its spectral position.The destructive interference of multipoles leads to zero net-radiation and strong field trapping.Such radiationless states disappear in the far-field,localize enhanced near-field and can be excited in nanostructures.On the other hand,the optical modes turn out to be completely confined due to no losses at discrete point in the radiation continuum,such states result in infinite Q-factor and lifetime.The radiationless states provide a suitable platform for enhanced light matter interaction,lasing,and boost nonlinear processes at the state regime.These modes are widely investigated in different material configurations for various applications in both linear and nonlinear metasurfaces which are briefly discussed in this review.
基金supported by the Beijing Outstanding Young Scientist Program(Grant No.BJJWZYJH01201910007022)the National Natural Science Foundation of China(Grant Nos.61775019,and 92050117)the National Postdoctoral Program for Innovative Talents of China(Grant No.BX20200050)。
文摘Weyl points,which are the degenerate points in three-dimensional momentum space,have been widely studied in the photonic system,and show some intriguing phenomena such as topologically protected surface states and chiral anomalies.Type-I Weyl systems possess a complete bandgap,and topologically protected surface states can be excited without disturbing the bulk states.In this work,we investigate the influence of the sign of coupling coefficient on the topological property of the system and find that type-I Weyl points can be realized by introducing a negative coupling between the stacking layers of the designed photonic crystal.We propose a new strategy to construct a type-I Weyl system by stacking the hexagonal photonic lattice.Different from the topological nontrivial photonic system with a positive coefficient,the negative couplings in the photonic system are realized by adding another resonating site between stacking layers.We theoretically demonstrate that the effective coupling between the resonating sites in adjacent layers sign-flips through the judicious design of the nearest coupling strength and eigenfrequency of the additional sites.The surface states at opposite boundaries of the proposed system have opposite group velocities,which is the feature of type-I Weyl points.Our study provides a new method of exploring topologically protected photonic systems and developing possible topological devices.
