Frontiers in Physics (Jul 2021)

Beam Splitters Fabricated by Nonlinear Focusing of Femtosecond Laser Writing in Pure YAG Crystal

  • Pengfei Wu,
  • Pengfei Wu,
  • Senchi Yang,
  • Yingying Ren,
  • Hongliang Liu

DOI
https://doi.org/10.3389/fphy.2021.719757
Journal volume & issue
Vol. 9

Abstract

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We report on the fabrication of waveguides and beam splitters in pure YAG crystals by femtosecond laser direct writing (FLDW). During the femtosecond laser writing process, a positive refractive index is induced through the nonlinear focusing above the focus position, resulting in an unusual guiding cross-sectional configuration. The supported guiding modes at 632.8 nm are measured and analyzed using the end–face coupling system. The propagation loss can be as low as 1.9 dB/cm for the single-line waveguide. Different from the geometry of the traditional fs-laser modified area, this novel structure might offer a new approach in the quest toward integrated photonics.

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