Cavity-Enhanced Second-Order Nonlinear Photonic Logic Circuits

A large obstacle for realizing photonic logic is the weak optical nonlinearity of available materials, which results in large power consumption. In this paper, we present the theoretical design of all-optical logic with second-order (χð2Þ) nonlinear bimodal cavities and their networks. Using semiclassical models derived from the Wigner quasiprobability distribution function, we analyze the power consumption and signal-to-noise ratio (SNR) of networks implementing an optical AND gate and an optical latch. A comparison between the secondand third-order ðχð3ÞÞ optical logic reveals that, while the χð3Þ design outperforms the χð2Þ design in terms of the SNR for the same input power, employing the χð3Þ nonlinearity necessitates the use of cavities with ultrahigh-quality factors (Q ∼ 10) to achieve a gate power consumption comparable to that of the χð2Þ design at significantly smaller quality factors (Q ∼ 10). Using realistic estimates of the χð2Þ and χð3Þ nonlinear susceptibilities of available materials, we show that, at achievable quality factors (Q ∼ 10), the χð2Þ design is an order of magnitude more energy efficient than the corresponding χð3Þ design.