Integrated optical circuits with nanophotonic devices have attracted significant attention due to their low power dissipation and light-speed operation. With light interference and resonance phenomena, the nanophotonic device works as a voltage-controlled optical pass-gate like a pass-transistor. This article first introduces the concept of optical pass-gate logic and then proposes a parallel adder circuit based on optical pass-gate logic. Experimental results obtained with an optoelectronic circuit simulator show the advantages of our optical parallel adder circuit over a traditional CMOS-based parallel adder circuit.

In photonic crystal (PC) microlasers with point defect cavities, effective carriers are reduced by the leakage to outside of the defect, surface recombination, spatial carrier hole burning, and Auger recombination. To estimate these effects, we calculated carrier and photon behavior by solving two-dimensional rate equations in space and time domains. The result clearly shows these effects and their dependence on cavity structure, pump area, and so on. Compared with that for the microdisk laser, higher threshold values are estimated for PC microlasers. However, a comparably low threshold density and a high efficiency are expected for the quasi-periodic PC microlaser, because the hole burning by the whispering gallery mode of this cavity suppresses the carrier leakage.