Abstract
An 80 MHz pulse train of ~ 100 fs optical pulses centred at ~ 1.5 microm is propagated through a variety of high-index-contrast silicon-on-insulator waveguide structures less than 1 mm long. All-optical power limiting and negative differential transmission, based only on the intrinsic nonlinear response of the untextured waveguides near 1.5 microm, are demonstrated for average in-guide power levels of ~ 1 mW. Superlinear transmission is observed in a textured silicon waveguide for power levels less than 20 microW.
Highlights
Photonic crystals, or, more generally, high-index-contrast (HIC) optical waveguides, offer a means by which to integrate a number of signal processing functions in small (~cm2) “optical chips”
Numerous geometries have been proposed for realizing the key building blocks of integrated optical chips in HIC waveguides, including; high-transmission bends, splitters, dispersion compensators, filters etc [1]
This paper describes a number of nonlinear responses obtained by propagating an 80 MHz pulsetrain of ~ 100 fs optical pulses centred at ~ 1.5 μm, through HIC integrated silicon waveguide structures less than 1 mm long
Summary
More generally, high-index-contrast (HIC) optical waveguides, offer a means by which to integrate a number of signal processing functions in small (~cm2) “optical chips” This is fundamentally due to the fact that optical pulses propagating in these stronglyconfining, dispersive waveguides can be efficiently filtered and re-routed over distances of only a few wavelengths, with low intrinsic loss. Published [8] nonlinear propagation studies of ~ 100 fs pulses through 200 nm high by 1.6 μm wide silicon ridge waveguides illustrated how compact optical limiters can be realized in SOI These proof-of-principle devices incorporated 2D photonic crystal input and output “grating” couplers, combined with parabolic-shaped taper sections that adiabatically couple the ~ 10 μm wide output of the grating coupler into the narrow ridge waveguides [8]. The principles used to achieve these nonlinear transmission responses are quite generic: qualitatively similar, and perhaps even better nonlinear behaviour could be expected in HIC waveguides made from other semiconductors, such as AlxGa1-xAs, or by integrating resonant media, such as semiconductor quantum dots, with the waveguides
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