Origin of reciprocal circular birefringence observed in X-cut, Z-propagation LiNbO3 polarization transformers

Polarimetric investigation reveals up to ≈ 2 rad of reciprocal circular retardation present in 10 commercial X-cut, Z-propagation LiNbO₃ polarization transformers from two suppliers. A recent experiment confirms the static polarization mode coupling observed in polarization transformers which are fabricated in-house using either off-axis or principal-axis propagation. Optical activity is responsible for the nonideal behavior of the integrated electro-optic waveplates. This phenomenon is explained and accurately modelled using LiNbO₃ anisotropy. Furthermore the procedure required to make the polarization transformers ideal is given. Received: 16 May 2001 / Revised version: 9 August 2001 / Published online: 23 October 2001