Novel optical polarization splitter in lithium niobate

A tunable Y-branch Ni:LiNbO3 polarization (mode) splitter with a ridged input arm is presented. The ridge is used to lower the tuning voltage and thus enhance the tuning flexibility of the polarized fields. To improve the confinement of Ni-indiffused waveguide, Zn and Ni are both diffused at the same time. To use the electro-optic modulation, the polarization splitter is implemented in a Z-cut Y-propagating LiNbO3. Experimental results show that the tuning voltage can be reduced by a factor of about 1/3 with a ridge of height 2mum. The measured extinction ratio is 21dB for the transverse electric (TE) mode and 18dB for the transverse magnetic (TM) mode.