Continuous-wave Raman amplification in silicon waveguides: beyond the undepleted pump approximation

We present approximate analytical expressions describing nonlinear interaction of two optical waves co-propagating inside a silicon waveguide in the presence of linear losses, stimulated Raman scattering, and free-carrier absorption. Our approach avoids the undepleted-pump approximation, which we show to be inadequate to describe accurately the Raman-gain process. Based on our calculations, we propose a new generalized definition for the effective length and show that it provides better insight into the impact of nonlinear absorption on Raman amplification in silicon waveguides. (C) 2009 Optical Society of America