All-optical Logic Gates Based On Electro-optic Effect In Periodically Poled Lithium Niobate

In order to breakthrough"electronic bottleneck"constraints, all-optical technology as the basis of future all-optical communication networks is becoming more and more attractive. As the core device in the all-optical technology, the all-optical logic gates have wide applications in optical packet switching, optical computing and optical signal regeneration. The realization of all-optical logic gates is mainly using the nonlinear optical properties of high nonlinear materials, such as nonlinear fiber materials, nonlinear optical crystal and semiconductor optical amplifier, etc.The traditional all-optical logic gates are mainly based on the intensity encoding program, which using the intensity of the optical signal to represent logic 0 and logic 1 of the digital signal. Under logic signal processing, due to the limitations of conversion efficiency of nonlinear optical effect, the intensity of optical signal will inevitably be greatly attenuated. Therefore, the regeneration and amplification of optical signal is needed, which greatly increase complexity and operating costs of all-optical communication networks.A simple approach based on polarization to process binary all-optical logic signal with validation is proposed, by electro-optic Pockels effect. In experiment, we choose optical signal with two orthogonal linear polarization states to present logic 1 and logic 0. This approach can alter the polarization state of input optical signal about 90°on the polarization plant based on electro-optic modulation of periodically poled lithium niobate (PPLN). Optical signal can be switched between the two orthogonal polarization states, and will be no changed without external applied electric field. Therefore, it can realize controlled-NOT function. If we choose external applied electric field to present logic 1 and logic 0, it can realize NOR and XNOR functions. In this approach, digital logic signal is carried on the polarization-state of optical signal. The dissipation of intensity of optical signal is very small in this process, so this approach is more advantageous for multiply cascaded systems, comparing with traditional approach ,in which digital logic signal is carried on the intensity of optical signal.