Large Silicon Photonic Gratings with High Directionality for FSO and LiDAR Applications

Abstract

Traditionally, studies on grating couplers have focused on achieving high coupling efficiency for chip-to-fibre grating coupler or obtaining large MFD or high directionality separately, which has resulted in less-than-ideal solutions for applications like LiDAR systems and FSO communication. This thesis is done with collaboration with UMA, Malaga with design rule contraints of Applied Nanotools. It focuses on the simultaneous optimization of grating couplers for both large MFD and high directionality, filling a substantial research gap in the field of optical grating coupler design. By creating innovative grating coupler designs that can effectively achieve high directionality greater than 70%, and support larger MFD > 150 µm, this work seeks to close this gap. The thesis starts with a thorough analysis of the MFD and directionality constraints of the current grating coupler designs. The design process used to simultaneously optimize these parameters is then presented, taking into account elements like the grating period, etch depth, duty-cycle and material system. The suggested grating coupler designs are simulated and experimentally validated through the use of sophisticated modeling methods. In comparison to traditional designs, the results show significant improvements in both MFD > 150 µm and directionality > 70%. The improved grating coupler designs work better, allowing for effective light transmission and reception over extended distances while retaining perfect directionality applicable for FSO communication and LiDAR applications.