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.