Efficient and Broadband Four-Wave Mixing in a Compact Silicon Subwavelength Nanohole Waveguide

Confining light in a small volume offers an effective approach to enhance the four-wave mixing (FWM) process. Recently, most efforts are devoted to improve the conversion efficiencies by using resonant structures. As a result, the bandwidths of the FWM conversions are typically limited to 1-2 nm. In this paper, a nonresonant silicon subwavelength nanohole waveguide is proposed to manipulate the field distribution of the propagating wave. The electromagnetic field of the Bloch mode can be engineered to concentrate in the silicon area where the FWM process occurs. Benefiting from the enhanced light intensity, an efficient and broadband FWM process is experimentally demonstrated. A conversion efficiency of -26.7 dB is achieved with a carefully designed silicon nanohole waveguide, showing a 12.5 dB improvement relative to a conventional silicon strip waveguide. The 3 dB conversion bandwidth of the silicon nanohole waveguide is approximate to 37 nm, limited by the optical amplifiers employed in the experiment.