Analysis of First-Order Gratings in Silicon Photonic Waveguides

A simple thin film effective index analysis for first-order gratings in Si photonic waveguides is shown to provide highly accurate results reflected and transmitted power spectrums as long the waveguide remains single mode non-radiating. cover layer can be added grating region of a increase strength grating, modify transition losses from input region, and/or width reflectivity spectrum. For given period, peak reflection spectral decrease duty cycle decreased or increased ∼50%. both radiating multimode structures, coupling between all modes, radiated towards superstrate (upwards), downwards (substrate) analyzed by Floquet-Bloch, Eigenmode Expansion Finite Difference Time Domain methods show excellent agreement. Coupling coefficients calculated using analytic formulas are only shallow depths.