Abstract
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 language | English |
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Article number | 125243 |
Journal | Optics Communications |
Volume | 461 |
Early online date | 7 Jan 2020 |
DOIs | |
Publication status | Published - 15 Apr 2020 |
Keywords
- 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