Focusing 1D Silicon Photonic Grating Coupler in Photonic BiCMOS Technology for the Excitation of the Fundamental TM Mode

A focusing 1D grating coupler is designed to interface a transverse-magnetic mode between a single-mode fiber and a silicon photonic nanowire. A theoretical coupling loss of -4 dB at a wavelength of 1550 nm is obtained. The proposed design is fabricated in a full-featured electronic photonic integrated circuit technology (photonic BiCMOS) and characterized experimentally for different coupling angles. Measurements show a coupling loss of -4.6 dB at 1555 nm and -4.3 dB at 1570 nm. Further designs are proposed for future fabrication and experiments.