Engineering optical nonlinearities in silicon–nanocrystal waveguides

Abstract

The strength of the nonlinear optical effects in silicon-nanocrystal waveguides can be varied as required for applications by altering the geometry of the waveguide and the composition of its nonlinear core. By studying theoretically the geometric and composition dependencies of the mode overlap factors responsible for the nonlinear interaction between the pump and Stokes optical fields, which are separated by the Raman shift in silicon, we demonstrate that this strength can be varied in a wide range, thus offering broad opportunities for engineering optical nonlinearities in silicon-nanocrystal waveguides. The numerically calculated mode overlap factors are useful in modeling light propagation through nonlinear silicon-nanocrystal waveguides governed by the recently derived generalized nonlinear Schrödinger equations.

Modeling nonlinear optical phenomena in silicon-nanocrystal composites and waveguides

“…γ pp yy , γ ps yy , γ sp yy , and γ ss yy ) and two effective mode indices (n py and n sy ) [50]. Numerical simulations show that in this instance they range from about 0.1 to 1 and from 1 to 2.4, respectively, and are functions of the slot width and thickness, and the volume fraction of the silicon nanocrystals [83].…”

“…The number and values of relevant effective mode indices and mode-overlap factors critically depend on the wave propagation conditions [83]. If a pair of optical fields, say, pump (µ = p) and signal (µ = s), interact in the form of linearly polarized beams inside an unbounded silicon-nanocrystal composite, then there are 48 generally different mode-overlap factors (γ µµ νν , λ µµ νν , and ψ µµ νν with µ, µ = p, s and ν, ν = x, y) and four generally different effective mode indices (n px , n py , n sx , and n sy ).…”