Fig. 1. Schematic illustration of a typical experimental setup for FsLDW operation.

Fig. 2. Schematic illustrations FsLDW of (a) single-line waveguides based on smooth Type-Ⅰ modification, (b) stress-induced double-line waveguides based on two parallel Type-Ⅱ laser tracks, and (c) depressed-cladding waveguides.

Fig. 3. Schematic illustration of nonlinear waveguide channels based on FsLDW single-/multi-line geometries.

Fig. 4. (a) Schematic illustration of Y-branch waveguide channels based on FsLDW double-line geometry³⁹. (b) The microscopic photograph of the splitting region in a FsLDW Yb:YAG waveguide splitter³⁹. (c) The cross-sectional microscopic photograph of a FsLDW Nd:YAG waveguide array⁴³. (d) Reconstructed refractive index profile of the fabricated waveguide array⁴³. Scale bars denote 30 µm. Figure reproduced with permission from: (a, b) ref.³⁹ and (c, d) ref.⁴³, Optical Society of America.

Fig. 5. (a) Schematic illustration of curved waveguide channels based on FsLDW depressed-cladding geometries³⁴. (b) Schematic illustration of three-element 3D photonic-lattice-like cladding photonic structures for beam splitting and ring-shaped beam transformation³¹. Figure reproduced with permission from: (a) ref.³⁴, SPIE; (b) ref.³¹, Optical Society of America.

Fig. 6. Schematic illustration of a MZI EO modulator with Y-branch waveguide channels based on FsLDW double-line geometries⁵⁸. Figure reproduced with permission from ref.⁵⁸, Optical Society of America.

Fig. 7. (a) Lasing performance of FsLDW curved Yb:YAG double-line waveguides with different curvature radii R³⁸. (b–e) Output modal profiles of FsLDW beam splitters and ring-shaped beam transformers^{49, 50}. Figure reproduced with permission from: (a) ref.³⁸, Optical Society of America; (b, e) ref.⁴⁹, Springer Nature; (c, d) ref.⁵⁰, IEEE.

Fig. 8. Modal profiles of SHG (1064→532 nm) and 1×4 beam splitting from photonic-lattice-like KTP cladding waveguides⁶⁹. Figure reproduced with permission from ref.⁶⁹, Springer Nature.

Table 1. EO performance of reported FsLDW Y-branch waveguides in crystals.

Table 2. Lasing performance of reported FsLDW 3D waveguides in crystals.