Broadband, tunable wavelength conversion using tapered silicon fibers extending up to 2.4 μm

Wavelength conversion via four-wave mixing holds great promise for the construction of broadband and tunable light sources at wavelengths beyond 2 μm. In this work, we design and fabricate a tapered silicon core optical fiber with a dispersion profile that supports efficient conversion spanning the telecom band up to the edge of the mid-infrared spectral region over an extended propagation length. By pumping with a fiber laser centered around 1.99 μm, a tuning range of 690 nm has been measured, although simulations predict that a bandwidth of up to 1255 nm could be observed if a suitable seed source was available. Conversion efficiencies of ∼−30 dB have been obtained over a bandwidth of 380 nm when using an input pump power of only 6 dBm, with a maximum efficiency of −18 dB achieved when the conversion overlaps the strong Raman gain of the silicon core.