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| 1 | Direct quantification of topological protection in symmetry-protected photonic edge states at telecom wavelengths显示文摘Topological on-chip photonics based on tailored photonic crystals(PhCs)that emulate quantum valley-Hall effeas has recently gained widespread interest owing to its promise of robust unidirectional transport of classical and quantum information.We present a direct quantitative evaluation of topological photonic edge eigenstates and their transport properties in the telecom wavelength range using phase-resolved near-field optical microscopy.Experimentally visualizing the detailed sub-wavelength structure of these modes propagating along the interface between two topologically non-trivial mirror-symmetric lattices allows us to map their dispersion relation and differentiate between the contributions of several higher-order Bloch harmonics.Selective probing of forward-and backward-propagating modes as defined by their phase velocities enables direct quantification of topological robustness.Studying near-field propagation in controlled defects allows us to extract upper limits of topological protection in on-chip photonic systems in comparison with conventional PhC waveguides.We find that protected edge states are two orders of magnitude more robust than modes of conventional PhC waveguides.This direct experimental quantification of topological robustness comprises a crucial step toward the application of topologically protected guiding in integrated photonics,allowing for unprecedented error-free photonic quantum networks。 | Sonakshi Arora Thomas Bauer Rene Barczyk Ewold Verhagen L.Kuipers | 2021 | Light(Science & Applications)2021，10，1： | 2 |
| 2 | Radiationless anapole states in on-chip photonics显示文摘High-index nanoparticles are known to support radiationless states called anapoles,where dipolar and toroidal moments interfere to inhibit scattering to the far field.In order to exploit the striking properties arising from these interference conditions in photonic integrated circuits,the particles must be driven in-plane via integrated waveguides.Here,we address the excitation of electric anapole states in silicon disks when excited on-chip at telecom wavelengths.In contrast to normal illumination,we find that the anapole condition-identified by a strong reduction of the scattering-does not overlap with the near-field energy maximum,an observation attributed to retardation effects.We experimentally verify the two distinct spectral regions in individual disks illuminated in-plane from closely placed waveguide terminations via far-field and near-field measurements.Our finding has important consequences concerning the use of anapole states and interference effects of other Mie-type resonances in high-index nanoparticles for building complex photonic integrated circuitry. | Evelyn Diaz-Escobar Thomas Bauer Elena Pinilla-Cienfuegos Angela I.Barreda Amadeu Griol L.Kuipers Alejandro Martinez | 2021 | Light(Science & Applications)2021，10，11： | 0 |
| 3 | A full vectorial mapping of nanophotonic light fields显示文摘Light is a union of electric and magnetic fields,and nowhere is the complex relationship between these fields more evident than in the near fields of nanophotonic structures.There,complicated electric and magnetic fields varying over subwavelength scales are generally present,which results in photonic phenomena such as extraordinary optical momentum,superchiral fields,and a complex spatial evolution of optical singularities.An understanding of such phenomena requires nanoscale measurements of the complete optical field vector.Although the sensitivity of nearfield scanning optical microscopy to the complete electromagnetic field was recently demonstrated,a separation of different components required a priori knowledge of the sample.Here,we introduce a robust algorithm that can disentangle all six electric and magnetic field components from a single near-field measurement without any numerical modeling of the structure.As examples,we unravel the fields of two prototypical nanophotonic structures:a photonic crystal waveguide and a plasmonic nanowire.These results pave the way for new studies of complex photonic phenomena at the nanoscale and for the design of structures that optimize their optical behavior. | B.le Feber J.E.Sipe M.Wulf L.Kuipers N.Rotenberg | 2019 | Light(Science & Applications)2019，8，1： | 0 |
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