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All-optical half adder using quantum dot semiconductor optical amplifier is proposed and analyzed using numerical simulations for two different unsaturated gains. Cross gain modulation (XGM) and cross phase modulation (XPM) in Mach–Zehnder interferometer structure generate CARRY and SUM, respectively, of the half adder. The performance of the device is optimized with respect to input pump powers and effect of amplified spontaneous emission (ASE) noise is also investigated. We have found extinction ratio (ER) as high as 16.48 dB for SUM and 12.95 dB for CARRY which ensures efficient performance of the proposed half adder. The quality factor Q is also high (24.58 dB for SUM and 18.47 dB for CARRY). These confirm clear transmissions of the bits with low bit error rate (BER).

Present communication deals with the design and analysis of all-optical NOR and NAND gates using Quantum dot Semiconductor Optical Amplifiers (QDSOA). The design uses no interferometer structure but cross gain modulation is utilized for operation. The structures are simple and simulations at a rate of 1 Tb/s are processed. For unsaturated gain 30 dB, the logic gates show high values of ER (29.82 dB, 16.93 dB), CR (29.6 dB, 21.33 dB), and Q (25.4 dB, 13.2 dB). This ensures practical feasibility and high quality of the proposed gates.

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