Document Type : Research article


1 Young Researchers and Elite Club, Tabriz Branch, Islamic Azad University, Tabriz 5157-944533, Iran

2 Department of Electrical Engineering, Shahrekord Branch, Islamic Azad University, Shahrekord 8813-733395, Iran


This paper reports a new optical half-adder design using linear defects in a photonic crystal (PhC) structure. The half adder's proper design obviates the need to increase the input signal's intensity for the nonlinear optical Kerr effect's appearance, which leads to the diversion of the incoming light toward the desired output. The proposed device is composed of silicon rods consisting of four optical waveguides and a defect in a PhC. Two well-known plane wave expansion and finite difference time domain methods are used to study and analyze photonic band structure and light propagation inside the PhC, respectively. The numerical results demonstrate that the ON-OFF contrast ratios are 16 dB for “Sum” and about 14 dB for "Carry".  They also reveal that the proposed half-adder has a maximum time delay of 0.8 ps with a total footprint of 158 µm2. Due to very low delay time, high contrast ratio, and small footprint, they are more crucial in modern optoelectronic technologies, so this structure can be used in the next generation of all-optical high-speed central processing units.


  • An ultrafast optical half-adder based on linear defects in a photonic crystal microstructure.
  • The maximum rise time of the proposed half-adder is just about 0.8 ps.
  • The total footprint of the structure is 158 µm2.
  • There is no need to increase the input intensity for the appearance of the nonlinear effect.
  • The ON-OFF contrast ratios for Sum and Carry are 16dB and 14dB, respectively.


Main Subjects