An Optical Feynman Gate Using Cascaded Ti:LiNbO3 Directional Couplers

Currently reversible logic has gained lot of interest and it is a reliable solution for optical computing, low-power CMOS, quantum computing and nanotechnology. Being reversible logic, one-to-one mapping between input and output causes minimal loss of information. In fact, optical Feynman gate (FG), one among many reversible logic gates, is a potential candidate for the realization of low power photonic computational circuits. In this paper, we propose and demonstrate an optical FG using four titanium indiffused lithium niobate (Ti:LiNbO3) directional couplers. Design of the integrated-optic chip was performed using Effective-Index based Matrix Method (EIMM). The proof-of-concept of the proposed optical Feynman gate was experimentally verified using Z-cut LiNbO3 substrate. The fabricated device has an insertion loss of ~12.5 dB at TM polarization. The switching voltage of each directional couplers in the chip were around 1.5 V without any buffer layer. The foot-print of the device is 23.8 mm × 0.63 mm.