All-optical, polarization-independent switching using the Sagnac interferometer

Abstract

Polarization-dependent operation is a serious obstacle in the development of practical photonic devices. In photon-photon devices polarization dependence can arise from different reasons. For example, orthogonal linear polarizations are often used to isolate the two input channels of a three terminal device. In such a case polarization dependence is essential for proper operation of the circuit. Also, in devices where interferometry is used, the polarization of the signal and reference beams must be the same or the interference is incomplete. Schemes such as polarization diversity do not work with nonlinear optical devices, as the interaction is intensity dependent. One successful approach is active polarization control, which requires detection and control circuitry combined with a LiNbO3 electrooptic polarization controller [1]. Active control however, entails extra complexity and expense, and the difficulty involved leads one to the search for simpler schemes.