Research on all-optical half adder based on cross-gain modulation in quantum-dot semiconductor optical amplifier

An all-optical half adder has been achieved successfully by using gain nonlinearity characteristics of cross-gain modulation in quantum-dot semiconductor optical amplifier. In this design, no additional input beam is required, which is simpler and more compact compared to designs based on two or more interferometer switches. By optimizing the geometry of the multimode interference area to manipulate the position of the imaging point, a power splitter with an arbitrary splitting ratio is achieved, fulfilling the system's splitting requirements. The pattern effect, contrast ratio and output extinction ratio at different splitting ratios are compared. The effect of key parameters on the Q factor is compared and analyzed. The results demonstrate that the scheme can realize all-optical half adder with logical correctness and a high Q factor. Through parameter optimization, the Q factor can be improved by about 9 dB than the other half adders based on QD-SOA.