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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Experimental Realization of Two-Dimensional PT-Symmetric Graphene: Bulk Properties and Edge States
摘要： The condition of real eigenvalue spectra in quantum mechanics is usually met by requiring operators to be Hermitian. This perception was challenged in 1988 by Carl M. Bender and Stefan Boettcher, who showed that parity-time (PT) symmetric Hamiltonians can have real spectra as well [1]. In photonics this concept was adopted by designing gain and loss structures for electromagnetic waves [2]. While numerous hallmark features [2] could be verified, experiments remained limited to one-dimensional settings. In this work we overcome this limitation and demonstrate a two-dimensional PT-symmetric system of photonic waveguides. We use this structure to study the interplay between a PT-phase transition and the emergence of topological edge states.
关键词： photonic waveguides,PT-symmetry,two-dimensional systems,topological edge states
更新于2025-09-16 10:30:52
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Mode-crossing spectroscopy for photonic waveguide characterization
摘要： We report a novel spectroscopic technique to characterize photonic waveguides over more than an octave of wavelength. The technique, called mode-crossing spectroscopy, uses a broadband source and a spectrometer that are coupled to the input and output ends of a series of straight dielectric waveguides via single-mode optical fibers. Measurements of the wavelengths at which multiple modes are degenerate in a single waveguide enable the determination of the refractive index of the core, as well as the waveguide width variation. In addition, mode-dependent losses are reported from 700 nm to 1550 nm using waveguides of varying lengths. The core refractive indices are measured within an error of ±0.5%, waveguide width variation to an accuracy of less than 5 nm, and waveguide propagation losses within an error of ±0.5 dB/cm. Ultrabroadband in situ measurements of loss and index over an octave of bandwidth are crucial for the accurate characterization of photonic integrated circuits and devices, especially those based on precision broadband couplers, interferometers, and resonant cavities.
关键词： propagation losses,mode-crossing spectroscopy,photonic waveguides,waveguide width variation,refractive index
更新于2025-09-16 10:30:52
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Corner states of light in photonic waveguides
摘要： The recently established paradigm of higher-order topological states of matter has shown that not only edge and surface states but also states localized to corners, can have robust and exotic properties. Here we report on the experimental realization of novel corner states made out of visible light in three-dimensional photonic structures inscribed in glass samples using femtosecond laser technology. By creating and analysing waveguide arrays, which form two-dimensional breathing kagome lattices in various sample geometries, we establish this as a platform for corner states exhibiting a remarkable degree of flexibility and control. In each sample geometry we measure eigenmodes that are localized at the corners in a finite frequency range, in complete analogy with a theoretical model of the breathing kagome. Here, measurements reveal that light can be ‘fractionalized,’ corresponding to simultaneous localization to each corner of a triangular sample, even in the presence of defects.
关键词： corner states,breathing kagome lattices,femtosecond laser technology,higher-order topological states,photonic waveguides
更新于2025-09-11 14:15:04