Double-Track Waveguides inside Calcium Fluoride Crystals

• Main Authors: Wendwesen Gebremichael, Lionel Canioni, Yannick Petit, Inka Manek-Hönninger
• Format: Article
• Language: English
• Published: MDPI AG 2020-02-01
• Series: Crystals
• Subjects: femtosecond lasers; direct laser writing (dlw); micro-processing; photonic device; cubic crystal; waveguides; double-track; calcium fluoride; refractive index change; quantitative phase imaging
• Online Access: https://www.mdpi.com/2073-4352/10/2/109

Calcium Fluoride (CaF₂) was selected owing to its cubic symmetry and excellent luminescence properties as a crystal of interest, and ultrafast laser inscription of in-bulk double-track waveguides was realized. The guiding properties of these waveguides in relation to the writing energy of the femtosecond pulse are presented. The modified double-track waveguides have been studied by systematic developments of beam propagation experiments and numerical simulations. Furthermore, an adapted model and concepts were engaged for the quantitative and qualitative characterization of the waveguides, particularly for the transmission loss measurements and the three-dimensional refractive index mappings of the modified zones. Additionally, polarization-dependent guiding was investigated.