Broadband Raman amplification in silicon

Raman gain is a useful nonlinear phenomenon that has made optically pumped silicon lasers and amplifiers a reality. Unfortunately, the bandwidth of Raman gain in silicon is normally rather limited, owing to the narrow Raman linewidths typical of crystalline materials. Here, we report Raman amplification in silicon with a spectrum that is modified by the simultaneous occurrence of self-phase-modulation. This combined nonlinear action produces a broad Raman gain spectrum from a narrowband pump source.