All-optical logic gates using spatio-temporal modulation

In recent years there has been a tremendous effort in proposing different types of tunable all-optical gates. However, the proposed devices can only be used to generate only one gate. Here we propose a new mechanism to device all-optical gates that can be used to assemble any type of optical gates including XOR, OR, NOT gates. Our logic gate is based on exceptional points induced in the spatiotemporally modulated waveguide with active susceptibility. Our specific modulation mechanism allows for unidirectional couplings between the three harmonics of the waveguide. By the right excitation of the waveguide at the fundamental harmonic and the third harmonic, we can obtain the desired second harmonic demonstrating the required output for the creation of XOR, OR, and NOT. Other types of gates such as AND, NAND, NOR, XNOR can be directly obtained from these three basic gates.