Design of Optical Tunable CNOT (XOR) and XNOR Logic Gates Based on   2D-Photonic Crystal Cavity Using Electro-Optic Effect
  We have proposed optical tunable CNOT (XOR) and XNOR logic gates using two-dimensional photonic crystal (2DPhC) cavities. Where, air rods with square lattice array have been embedded in Ag-Polymer substrate with refractive index of 1.59. In this work, we have enhanced speed of logic gates by applying two input signals with a phase difference at the same wavelength for 2DPhC cavities. Where, we have adjusted the phases of input and control signals equal with {\pi}/3 and zero, respectively. The response time of the structure and quality factor of the cavities are in the range of femtosecond and 2000, respectively. Then, we have used electro-optic property of the substrate material to change the cavities resonance wavelengths. By this means, we could design the logic gates and demonstrate a tunable range of 23nm for their operation wavelength. The quality factor and the response times of cavities remain constant in the tunable range of wavelength, approximately. The evaluated least ON to OFF logic-level contrast ratios for the XOR and XNOR logic gates are 25.45dB and 22.61dB, respectively. The bit rates of the proposed logic gates can reach up to higher than 0.166 P(Peta)bps values. According to the high rapid response time with acceptable quality factor of the PhC cavities, the proposed optical logic gates can be considered as appropriate candidates to be building blocks for applications such as optical integrated circuits and optical processors with an ultrahigh speed of data flow. 
Karim Abbasian, Rasool Sadeghi and Parvin Sadeghi
physics.optics