Open AccessAnalysis in reciprocal space of the band-pass filter effect in uniform and non-uniform grating couplers
Author(s) -
Luca Zagaglia,
Francesco Floris,
Peter O' Brien
Publication year - 2020
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/1548/1/012031
Subject(s) - bandwidth (computing) , finite difference time domain method , reciprocal lattice , grating , physics , fourier transform , photonic crystal , optics , passband , filter (signal processing) , computational physics , band pass filter , telecommunications , quantum mechanics , computer science , diffraction , computer vision
A detailed study on the origin of the bandwidth reduction in the Coupling- Efficiency (CE) spectrum for non-uniform grating couplers (nu-GCs) due to a band-pass filter effect is reported. This effect is deeply investigated through Finite Difference Time Domain simulations (FDTD) in order to look at the spatial Fourier Transform (sFT) of the nu-GC’s emission, which gives the energies and the wavevectors sustained by the overall structure. We show: how to evaluate the bandwidth from the sFT and how the band-pass filter effect arises from the sFT affecting the CE spectrum giving a physical insight on the bandwidth’s reduction. Moreover, we also point out how the concept of photonic crystal bandstructure can be applied for such nu-GCs and used as a powerful tool to describe the dispersion of the light inside these non periodic structures. Finally, both the sFT and the bandstructure approaches are shown to give the same outcomes in terms of the bandwidth evaluation and to be in agreement with the CE spectra’s behaviours. The entire analysis is proposed also for uniform-GC in order to directly compare the two different types of structures.