Ultra-fast all-optical full-adder based on nonlinear photonic crystal resonant cavities
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ORIGINAL PAPER
Ultra‑fast all‑optical full‑adder based on nonlinear photonic crystal resonant cavities M. J. Maleki1 · A. Mir1 · M. Soroosh2 Received: 26 October 2019 / Accepted: 12 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this paper, a new photonic crystal-based full-adder for the summation of three bits has been proposed. For realizing this device, three input waveguides are connected to the main waveguide. An optical power splitter is placed at the end of this waveguide. Concerning the amount of optical intensity inside this waveguide, two nonlinear resonant cavities transmit the waves toward the correct ports. When the cavities do not drop the optical waves, the splitter guides them toward the output ports. The maximum delay time of the presented structure is around 0.5 ps and shows the fastest response among the reported works. This improvement is obtained due to using the resonant cavities. The time analysis results in a maximum working frequency of 2 THz. Also, designing the structure in 93 µm2 demonstrates that it is more compact than the previous works. The normalized low and high margins are obtained around 10% and 85%, respectively. So, the proposed device is capable of considering optical processing circuits. Keywords Full-adder · Kerr effect · Photonic bandgap · Photonic crystal · Resonant cavity
1 Introduction Due to increasing demands for wide bandwidth and ultra-fast processing, many attempts have been made to design and develop the optical processing systems. One of the essential components in digital circuits is the full-adder. This device sums three bits and generates two output bits, sum and carry. The main challenge in designing n-bit full-adders is the latency of developing the carry bit for the next stages. The electrical full-adders suffer the mentioned latency when the number of bits is increased. Different ideas such as generating carry signals in the form of the optical waves [1] and designing plasmonic-based [2] and photonic crystalbased [3–7] structures have been proposed to overcome this challenge. Ying et al. [1] proposed an electro-optical modulator for generating the carry in optical waves. They used a continuous wave and modulated it as the optical carry for the next * M. Soroosh [email protected] 1
Faculty of Engineering, Lorestan University, Khorramabad, Iran
Department of Electrical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
2
stages. Although the electric signals modulate the carry, the output optical signal should be converted to the electric form. This issue has not been considered in their work. Concerning the reported time for the electro-optical modulators (50 ps), it seems that this idea will not be applicable to design the ultra-fast processors. Xie et al. [2] designed and fabricated the cross-connected plasmonic waveguides to utilize the all-optical full-adder. Two plasmonic nano-cavities were side-coupled with the output waveguides. These cavities were covered with high-nonlinear co
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