Silicon core fibers (SCFs) are emerging as a robust and flexible waveguide platform that can exploit the high nonlinear coefficients of silicon to perform compact nonlinear processing within an integrated fiber geometry . Optical parametric amplification (OPA) based on four-wave mixing (FWM) has been studied intensively over the past decade using chip-based silicon waveguides for a variety of telecommunication applications such as all-optical signal sampling, time-demultiplexing, pulse generation, and wavelength conversion. However, due to the strong nonlinear absorption associated with two photon and free carrier effects in silicon at telecom wavelengths, net on/off parametric gain has not been observed using a continuous-wave (CW) signal, and even when using pulses the gain has been limited to be 5.2dB . Here, by tapering the SCF to tailor the dimensions such that we can achieve high coupling efficiency into a core with a sub-micron-sized diameter, required to access the anomalous dispersion region, we demonstrate OPA with a positive on/off gain up to 6.6dB and bandwidth of more than 220nm. Eventually, when fully integrated with conventional fibers and components to improve the robustness of the system , we expect these tapered SCFs will find wide-ranging applications in areas that require efficient wavelength conversion across a broad spectral band.
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