Optical saturation characteristics of dual-and single-injection Ge-on-Si photodetectors

The optical saturation characteristics in the germanium-on-silicon(Ge-on-Si) photodetector are studied for the first time, to the best of our knowledge. The relationship between the optical saturation characteristics and the optical field distribution in the Ge layer is illustrated by the simulation. This theory is verified by comparative experiments with single-injection and dual-injection structures. The dual-injection photodetector with a more balanced and uniform optical field distribution has a 13% higher responsivity at low optical power and 74.4%higher saturation current at 1550 nm. At higher optical power, the bandwidth of the dual-injection photodetector is five times larger than that of the single-injection photodetector.     

A controllable coupling structure for silicon microring resonators based on adiabatic elimination

Optical microring resonators are extensively employed in a wide range of physical studies and applications due to the resonance enhancement property.Incorporating coupling control of a microring resonator is necessary in many scenarios,but modifications are essentially added to the resonator and impair the capability of optical enhancement.Here,we propose a flexible coupling structure based on adiabatic elimination that allows low-loss active coupling control without any modifications to the resonators.The self-coupling coefficient can be monotonically or non-monotonically controllable by the proposed coupler,potentially at a high speed.The characteristic of the coupler when implemented in silicon microring resonators is investigated in detail using substantiated analytical theory and experiments.This work provides a general method in coupling control while ensuring the resonance enhancement property,making active coupling control in a resonator-waveguide system feasible.