Dispersion controlling in strained silicon waveguides using sub-wavelength grating metamaterials
Abstract
We report on controlling of the group velocity dispersion in silicon (Si) strip waveguides, with refractive index engineered sub-wavelength grating (SWG) metamaterials, covered by silicon nitride (Si3N4) layer. This waveguide geometry is utilized for breaking the centrosymmetric nature of silicon and opening the route for second-order nonlinearities in the silicon-on-insulator technology. We show by calculations that attractive waveguide dispersion profiles over a broad spectral range can be flexibly tailored by proper control of transversal dimensions and appropriate refractive index engineering. Both normal and anomalous dispersion regimes can be obtained, being one important parameter for various nonlinear applications in photonics. Waveguide dispersion is an essential characteristic of nanophotonic structures and careful control of this property is of critical importance, playing significant role in development of photonic components using nonlinear processes [1]. Substantial efforts have been put forward in the last years, elaborating various approaches to control the group velocity dispersion, both theoretically and experimentally [2-7]. This particularly includes changing the transversal dimensions [2], utilizing of slot-assisted geometries [3], using conformal dielectric overlayers [4], or adding thin material layers [5,6]. Fig.
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