Photonic lattice-like waveguides in glass directly written by femtosecond laser for on-chip mode conversion

We report on a conceptually new type of waveguide in glass by femtosecond laser direct writing, namely, photonic lattice-like (PLLW). The PLLW’s core consists well-distributed and densified tracks with sub-micron size 0.62 µm width. Specifically, PLLW inscribed as hexagonal-shape input ring-shape output side was implemented to converse Gaussian mode doughnut-like mode, high conversion efficiency obtained low insertion loss 1.65 dB at 976 nm. This work provides freedom for design fabrication the refractive index profile waveguides resolution broadens functionalities application scenarios direct-writing future 3D integrated systems.