Wavelength selection in focusing non-uniform grating couplers: A coupling efficiency curve asymmetry and bandwidth analysis

We report a combined experimental and computational investigation of the multi-wavelength response of a series of focusing non-uniform grating couplers designed on multiple SOI thicknesses interfaced with two different fiber coupling schemes. In particular, we demonstrate either the existence of an asymmetry of the coupling efficiency curve shape, with respect to the tuning wavelength (1550 nm), related to the metastructure features, and how the photonic band structure of such metastructures can be calculated and exploited to evaluate their multi-wavelength response, in terms of multi-BW analysis. These results can be a positive stimulus for a further comprehension of the electromagnetic response of non-uniform grating couplers, particularly interesting as a valid option for integrated photonics applications.