Broadband silicon grating couplers with high efficiency and a robust design.

A record-high efficiency and bandwidth for a fiber-to-chip grating coupler have been achieved with a robust design and cost-effective fabrication on a silicon-on-insulator platform. The design optimization involves the usual geometrical parameters, period, and fill factor, and a mode matching for the fiber output and grating. The measured coupling efficiency for TE polarization and 1 dB bandwidth are -2.

Direct phase modulation via optical injection: theoretical study.

Direct phase modulation via optical injection is a newly developed method for coding the phase of a gain-switched laser, which meets high requirements placed on transmitters for quantum key distribution: compactness, low losses, compatibility with CMOS technologies, and the absence of undesirable effects leading to the side-channel information leakage. Despite the successful implementation and good prospects for the further development of this system, there is still a lack of theoretical investigations of this scheme in the literature. Here, for the first time, we perform its theoretical analysis.