Abstract
<p> <a href="http://oe.osa.org/virtual_issue.cfm?vid=36">Focus Serial: Frontiers of Nonlinear Optics</a> </p>Several kinds of nonlinear optical effects have been observed in recent years using silicon waveguides, and their device applications are attracting considerable attention. In this review, we provide a unified theoretical platform that not only can be used for understanding the underlying physics but should also provide guidance toward new and useful applications. We begin with a description of the third-order nonlinearity of silicon and consider the tensorial nature of both the electronic and Raman contributions. The generation of free carriers through two-photon absorption and their impact on various nonlinear phenomena is included fully within the theory presented here. We derive a general propagation equation in the frequency domain and show how it leads to a generalized nonlinear Schrodinger equation when it is converted to the time domain. We use this equation to study propagation of ultrashort optical pulses in the presence of self-phase modulation and show the possibility of soliton formation and supercontinuum generation. The nonlinear phenomena of cross-phase modulation and stimulated Raman scattering are discussed next with emphasis on the impact of free carriers on Raman amplification and lasing. We also consider the four-wave mixing process for both continuous-wave and pulsed pumping and discuss the conditions under which parametric amplification and wavelength conversion can be realized with net gain in the telecommunication band.
Highlights
Silicon photonics has attracted much attention recently because of its potential applications in the spectral region extending from near- to mid-infrared [1,2,3]
We derive a general propagation equation in the frequency domain and show how it leads to a generalized nonlinear Schrodinger equation when it is converted to the time domain
We consider first the impact of free carriers and show that, index changes induced by them have a negligible impact on four-wave mixing (FWM), free-carrier absorption limits the FWM efficiency so much that a net positive gain is difficult to be realized with continuous wave (CW) pumping in the telecommunication band
Summary
Silicon photonics has attracted much attention recently because of its potential applications in the spectral region extending from near- to mid-infrared [1,2,3]. Silicon exhibits a large third-order nonlinearity, with a Kerr coefficient more than 100 times larger [5] and a Raman gain coefficient more than 1000 times larger [6] than those of silica glass in the telecommunication band These features enable efficient nonlinear interaction of optical waves at relatively low power levels inside a short SOI waveguide (
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