Femtosecond laser inscribed Pr:CaF2 waveguides: Micro-spectroscopy characterizations and refractive index reconstruction

Taiyong Guo, Ruonan Li, Lifei Sun, Yangjian Cai*, Yingying Ren, Yicun Yao, Mark D. Mackenzie, Ajoy K. Kar

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


We report on the fabrication of dual-line waveguides with low propagation losses and single-mode guidance in Pr:CaF2 crystals by applying femtosecond laser inscription. In contrast to the typical highly elliptic modes previously reported in dual-line waveguides, the guiding mode obtained in our work is highly-localized with a near-circular profile at wavelength of 633 nm. The investigations on confocal micro-photoluminescence and micro-Raman imaging enable us to illustrate the effect of different femtosecond laser filamentations on the localized refractive index change in Pr:CaF2 crystals. In company with the mode simulation by finite element method, we further reconstruct the refractive index distribution of the fabricated waveguides. Our results indicate that highly-localized refractive-index increment caused by compressive stress between the lower parts of the filaments is the main mechanism for waveguiding, whereas the damage-induced refractive-index reductions at filaments and in the region between the upper parts of the filaments are responsible for the strong light confinement in both horizontal and vertical directions.

Original languageEnglish
Article number125243
JournalOptics Communications
Early online date7 Jan 2020
Publication statusPublished - 15 Apr 2020


  • Dual-line waveguides
  • Femtosecond laser inscription
  • Micro-spectroscopy imaging
  • Pr:CaF crystals
  • Refractive index reconstruction

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Physical and Theoretical Chemistry
  • Electrical and Electronic Engineering


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