| Over the last decade, the ultrafast laser has emerged as a powerful tool to shape three-dimensional photonic circuits in transparent dielectric materials. One of the unique traits of this fabrication approach is its ability to produce photonic circuits in bulk optical substrates with proven optical quality. It therefore bypasses all challenges associated with multi-step thin-film based material synthesis and fabrication techniques.;In this thesis, the ultrafast direct laser writing (DLW) technique is applied to several materials, including fused silica, lithium tantalate ( LiTaO3), sapphire (Al2 O3), and gallium lanthanum sulfide (GLS) chalcogenide glass to produce 3D photonic circuits. Optimal processing conditions are determined through the analysis of the guided-mode characteristics of these structures, while the mechanisms behind the laser-induced refractive index change are investigated with such techniques as micro-structural Raman imaging, and second-harmonic microscopy.;This research identifies optimized processing conditions by considering laser-induced multi-photon ionization, pulse distortion due to nonlinear Kerr interactions, and laser-induced thermal effects, all in connection with the intrinsic material properties. Based on this fundamental understanding of ultrafast laser material interactions, spatial and temporal pulse femtosecond time scales with micrometer spatial resolution. This work has yielded high quality low-loss photonic circuits in chalcogenide glasses for nonlinear and mid-IR applications. |
