Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultra-low-loss CMOS-Compatible Waveguide Crossing Arrays Based on
  Multimode Bloch Waves and Imaginary Coupling   We experimentally demonstrate broadband waveguide crossing arrays showing
ultra low loss down to $0.04\,$dB/crossing ($0.9\%$), matching theory, and
crosstalk suppression over $35\,$dB, in a CMOS-compatible geometry. The
principle of operation is the tailored excitation of a low-loss spatial Bloch
wave formed by matching the periodicity of the crossing array to the difference
in propagation constants of the 1$^\text{st}$- and 3$^\text{rd}$-order TE-like
modes of a multimode silicon waveguide. Radiative scattering at the crossing
points acts like a periodic imaginary-permittivity perturbation that couples
two supermodes, which results in imaginary (radiative) propagation-constant
splitting and gives rise to a low-loss, unidirectional breathing Bloch wave.
This type of crossing array provides a robust implementation of a key component
enabling dense photonic integration.

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The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
31
The categories of this paper are: ao-sci
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The categories of this paper are: q-alg