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The Hollow Core Light cage: Trapping Light Behind Bars
摘要： Optical waveguides represent the key element of integrated planar photonic circuitry having revolutionized many fields of photonics ranging from telecommunications, medicine, environmental science and light generation. However, the use of solid cores imposes limitations on applications demanding strong light-matter interaction within low permittivity media such as gases or liquids, which has triggered substantial interest towards hollow core waveguides. Here, we introduce the concept of an on-chip hollow core light cage that consists of free standing arrays of cylindrical dielectric strands around a central hollow core implemented using 3D nanoprinting. The cage operates by an anti-resonant guidance effect and exhibits extraordinary properties such as (1) diffractionless propagation in “quasi-air” over more than a centimetre distance within the ultraviolet, visible and near-infrared spectral domains, (2) unique side-wise direct access to the hollow core via open spaces between the strands speeding up gas diffusion times by at least a factor of 104, and (3) an extraordinary high fraction of modal fields in the hollow section (> 99.9%). With these properties, the light cage can overcome the limitations of current planar hollow core waveguide technology, allowing unprecedented future on-chip applications within quantum technology, ultrafast spectroscopy, bioanalytics, acousto-optics, optofluidics and nonlinear optics.
关键词： integrated photonics,anti-resonance guidance,leaky modes,Hollow core waveguide,3D nanoprinting,spectroscopy
更新于2025-09-23 15:23:52
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Avoided crossings and bound states in the continuum in low-contrast dielectric gratings
摘要： We consider bound states in the continuum (BICs) in low-contrast dielectric gratings. It is demonstrated that the BICs originate from the reduced guided modes on the effective dielectric slab with the permittivity equal to the average permittivity of the dielectric grating. In the case of isolated resonances, the positions of BICs can be found from two-wave dispersion relationships for guided leaky modes. In the case of the degeneracy between the two families of leaky modes, the system exhibits an avoided crossing of resonances. In the spectral vicinity of the avoided crossing the transmittance as well as the emergence of BICs is described in the framework of the generic formalism by Volya and Zelevinsky [Phys. Rev. C 67, 054322 (2003)] with a single fitting parameter.
关键词： leaky modes,dielectric gratings,bound states in the continuum,avoided crossings
更新于2025-09-23 15:21:21
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Analytic Mode Normalization for the Kerr Nonlinearity Parameter: Prediction of Nonlinear Gain for Leaky Modes
摘要： Based on the resonant-state expansion with analytic mode normalization, we derive a general master equation for the nonlinear pulse propagation in waveguide geometries that is valid for bound and leaky modes. In the single-mode approximation, this equation transforms into the well-known nonlinear Schr?dinger equation with a closed expression for the Kerr nonlinearity parameter. The expression for the Kerr nonlinearity parameter can be calculated on the minimal spatial domain that spans only across the regions of spatial inhomogeneities. It agrees with previous vectorial formulations for bound modes, while for leaky modes the Kerr nonlinearity parameter turns out to be a complex number with the imaginary part providing either nonlinear loss or even gain for the overall attenuating pulses. This nonlinear gain results in more intense pulse compression and stronger spectral broadening, which is demonstrated here on the example of liquid-filled capillary-type fibers.
关键词： resonant-state expansion,Kerr nonlinearity,leaky modes,nonlinear pulse propagation,waveguide geometries
更新于2025-09-23 15:21:21