Intermodal four-wave mixing in silicon waveguides

In this work, we report the modeling and the experimental demonstration of intermodal spontaneous as well asstimulated four-wave mixing (FWM) in silicon waveguides. In intermodal FWM, the phase-matching condition isachieved by exploiting the different dispersion profiles of the optical modes in a multimode waveguide. Since boththe energy and the wave vectors have to be conserved in the FWM process, this leads to a wide tunability of thegenerated photon wavelength, allowing us to achieve a large spectral conversion. We measured several waveguidesthat differ by their widths and demonstrate large signal generation spanning from the pump wavelength(1550 nm) down to 1202 nm. A suited setup evidences that the different waves propagated indeed on differentorder modes, which supports the modeling. Despite observing a reduced efficiency with respect to intramodalFWM due to the decreased modal overlap, we were able to show a maximum spectral distance between the signaland idler of 979.6 nm with a 1550 nm pump. Our measurements suggest the intermodal FWM is a viable meansfor large wavelength conversion and heralded photon sources. © 2018 Chinese Laser Press