All-optical logic gate in silicon nanowire optical waveguides

In this study, the authors propose a novel optical waveguide consisting of arrays of silicon nanowires (SiNWs) in close proximity for applications to all-optical logic operations. The logic operations are based on two non-linear phenomena, stimulated Raman scattering (SRS) and free carrier absorption (FCA). Since, the SRS coefficient is increased in the nanowire regime, the performance of the optical logic gates in terms of optical power required can be improved by a factor of at least 7 using our proposed waveguides. The advantage of the proposed waveguide is that it allows for increased photon-carrier interactions while keeping the optical confinement factor high even when the individual nanowire diameters are less than 100 nm. We analyse the waveguides using the finite-difference time domain method and show that the radiation loss is less than 0.034 cm^-1. Further, the waveguide allows for optical guidance even when the nanowires are randomly arranged. We also show a maskless etch method to create SiNWs with dimensions required to create our proposed waveguide structure.