High-performance femtosecond-laser microfabricated lattice-like-cladding waveguides in Er3+ and MgO co-doped LiNbO3 crystals for multi-wavelength guidance and luminescence

•The lattice-like-cladding waveguides with so-called Type II geometry support multi-wavelength guidance at near-infrared wavelength and mid-infrared wavelength.•The guidance is only along the perpendicular polarization.•The green up-conversion as well as the near-infrared luminescence were realized in the waveguides. We report on microfabrication of the straight and S-shaped waveguides with lattice-like-cladding structures in Er3+ and MgO co-doped LiNbO3 by femtosecond laser writing. The waveguides with so-called Type II geometry support fundamental-mode propagation of light at near-infrared wavelength of 1550 nm and mid-infrared wavelength of 4 μm, which was experimentally and numerically investigated. In addition, it has been found that the guidance is only along the perpendicular (i.e., TE) polarization, which can be produced through controlling the femtosecond laser’s parameters and direction. The green up-conversion at 550 nm under 4S3/2 → 4I15/2 transitions as well as the near-infrared luminescence at 1530 nm under 4I13/2 → 4I15/2 transition have been realized in the waveguides, and the resulting up-conversion luminescence efficiency was higher than Type I waveguides, which proved the Type II WGs can preserve and inspire the properties of the materials.