Integrated optical bypass-exchange switch in a single block of LiNbO 3 crystal

Abstract

Compact, low operating voltage, high-speed bypass-exchange switches are major elements in optical interconnection networks. Conventionally, a bypass-exchange switch consists of a controllable half-wave plate sandwiched between two polarizing beam displacers. In this paper, an integrated optical bypass-exchange switch is designed in a single block of LiNbO₃ crystal. The switch is polarization based and consists of only one birefringent crystal slab with electro-optic property. Based on both the phenomena of double refraction and internally double reflection, and the electro-optic effect in a crystal, an electro-optic modulator, a beam combiner and a beam splitter are integrated in a single block of LiNbO₃ crystal. The polarization states of the two input signals are both linear and perpendicular to each other. First the two signal beams are combined into a single channel with two orthogonal polarization directions by double refraction and internally double reflection. The signal couple propagates along the optical axis of the crystal. When a half-wave voltage is applied on the direction normal to the incident plane, the polarization directions of the two beams in a single channel will be exchanged. Last the signal couple is divided separately with the same deflection as that of the two input beams by double refraction and internally double reflection again. The experimental results show that the switch is low operating voltage, low cross talk, low energy loss, fast-speed, and insensitive to environment disturbance. The switch may be applied to the nodes of various multistage interconnection networks.