In this work, we have used femtosecond laser direct writing to inscribe guiding structures in y-cut LiNbO3 crystal and explored the mechanism of laser modification. Experimental results reveal the fabrication-parameter windows for the modifications with refractive index increase and decrease. We investigate the guiding properties under different polarizations at 632.8 nm. The spectral shifts of Raman modes have also been analyzed to clarify the laser-induced modifications on the crystal lattice. This study demonstrates that the lattice expansion and compression, and the damage induced by the laser energy are the key factors affecting the structural vibration and refractive index modification types.
We report on the fabrication of waveguides and beam splitters in pure YAG crystals by femtosecond laser direct writing (FLDW). During the femtosecond laser writing process, a positive refractive index is induced through the nonlinear focusing above the focus position, resulting in an unusual guiding cross-sectional configuration. The supported guiding modes at 632.8 nm are measured and analyzed using the end–face coupling system. The propagation loss can be as low as 1.9 dB/cm for the single-line waveguide. Different from the geometry of the traditional fs-laser modified area, this novel structure might offer a new approach in the quest toward integrated photonics.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.