Saturation of the Raman amplification by self-phase modulation in silicon nanowaveguides

TL;DR

This paper demonstrates that self-phase modulation, caused by Kerr effect and free-carrier refraction, limits the maximum Raman gain in silicon nanowaveguides, leading to saturation of amplification.

Contribution

It provides experimental evidence and a simple model linking self-phase modulation to Raman gain saturation in silicon nanowaveguides.

Findings

Self-phase modulation causes Raman gain saturation.

Measured spectra match the model predicting gain saturation.

Raman amplification is limited by nonlinear effects in silicon nanowaveguides.

Abstract

We experimentally show that the self-phase modulation of picosecond pump pulses, induced by both the optical Kerr effect and free-carrier refraction, has a detrimental effect on the maximum on-off Raman gain achievable in silicon on insulator nanowaveguides, causing it to saturate. A simple calculation of the Raman gain coefficient from the measured broadened output pump spectra perfectly matches the saturated behavior of the amplified Raman signal observed experimentally at different input pump powers.