Waveguide-to-Substrate Vertical Bend Coupler Design for 3D Photonic Integrated Circuits

A waveguide-to-substrate, vertical bend coupler that is based on genetic algorithm is introduced to couple and direct the optical flow in 3D photonic integrated circuits. The vertical coupler device enables high-efficiency broadband optical transmission between different dielectric layers over comparable distances to the coupler's length. The vertical coupler attains an adept transition between a silicon waveguide and a planar Si layer separated by a SiO2 spacer. The simulation results of the designed vertical coupler device show a coupling ratio of -3.4 dB at 1550 nm wavelength and at 1 mu m vertical transition depth, thanks to the effective manipulation of light. The coupler possesses a miniscule area of 2 mu m x 2 mu m compared to its conventional counterparts. Our proposed waveguide-to-substrate coupler represents an unprecedented, elevated solution with high- efficiency and broadband operation for the vertical transition in 3D photonic integrated circuits. It can take an important part in overcoming the obstacles on the way of 3D photonic integrated circuits for virtual reality and quantum computing applications.