Hybrid waveguiding structure in LiTaO3 crystal fabricated by direct femtosecond laser writing

•The opposite index changes for ne and no are realized in LiTaO3 by femtosecond laser writing.•The structure contains both ne and no waveguide cores separately.•Low-loss and non-distorted polarization sensitive beam splitter function has been realized.

A hybrid waveguiding structure has been fabricated in a z-cut lithium tantalate (LiTaO3) crystal wafer by direct femtosecond laser writing. Due to the laser-induced anisotropic modifications of the extraordinary and ordinary refractive indices (ne and no) of LiTaO3 crystal, the structure exhibits polarization-sensitive guiding features along vertical and horizontal orientations. Based on this feature, circularly-polarized light beam can be converted to vertically-/horizontally-polarized ones (i.e., TE and TM), with approximately 1:1 power splitting ratio. The well-guided performance of the polarization-sensitive structure shows the potential for integration with existing light signals to realize all-optical information processing.