Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Second-harmonic generation using 4-bar quasi-phasematching in a GaAs
  microdisk cavity   The 4-bar crystal symmetry in materials such as GaAs can enable
quasi-phasematching for efficient frequency conversion without poling, twinning
or other engineered domain inversions. 4-bar symmetry means that a 90 degree
rotation is equivalent to a crystallographic inversion. Therefore, propagation
geometries where light circulates about the 4-bar axis produce effective domain
inversions, useful for quasi-phasematching. Microdisk optical cavities also
offer resonance field-enhancement and excellent spatial overlap, resulting in
highly efficient frequency conversion in micrometer-scale volumes. These
devices can be integrated in photonic circuits as compact sources of radiation
or entangled photons. Efficient second-order frequency conversion is a new
functionality for nonlinear semiconductor microdisk resonators, which have been
previously explored for all-optical circuits as switches, signal routers and
optical logic gates. Arrays of microresonators can produce slow light and
robust optical delay lines. Here, we present the first experimental observation
of efficient second-harmonic generation in a microdisk cavity utilizing 4-bar
quasi-phasematching.

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The categories of this paper are: q-bio
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The categories of this paper are: atom-ph
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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: alg-geom
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: math
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex