ABSTRACT
Unfortunately, SRS in silicon waveguides competes with two nonlinear absorption e›ects at the standard telecom wavelengths around 1.5 µm. First, even though silicon is nominally transparent, the e›ect of two-photon absorption (TPA) becomes noticeable at the high optical powers necessary for Raman ampli„cation. In the TPA process, two photons are absorbed simultaneously, generating an electron-hole pair. e absorption caused by this e›ect alone does not impair the Raman-ampli„cation process signi„- cantly (Claps et al. 2002). However, the increased conductivity of the silicon waveguide due to TPA-generated charge carriers leads in turn to additional optical losses called free-carrier absorption (FCA), which can indeed be substantial (Liang and Tsang 2004) All these e›ects must be properly balanced in designing Ramanbased components in order to achieve optimum performance. e aim of this chapter is to give an overview over the known theoretical results that can help achieve this goal.
