Broadband MIR Wavelength Conversion in a Tapered Silicon Core Fiber

Silicon core fibers (SCFs) fabricated via the molten core drawing method (MCD) have emerged as a new platform for efficient four wave mixing (FWM) based wavelength conversion of optical data signals [1]. Thanks to the high nonlinearity of the core and the strong dispersion tailoring that is facilitated by the high core/cladding index contrast, both high gain [2] and broadband conversion [3] have been demonstrated in the telecoms band, despite the nonlinear absorption (two-photon and free carrier effects) that occurs in this spectral region. Here we build on this work to investigate FWM that extends into the mid-infrared (MIR), where the optical losses (both linear and nonlinear) of the SCFs are lower [4], and thus where the conversion efficiency (CE) and bandwidth are expected to improve. Specifically, we make use of a SCF that has been tapered to have a longitudinal profile that maximises the nonlinear conversion, but yet still offers low loss to the mid-infrared signal beams.