High Purcell Factor Achievement of Notched Cavity Germanium Multiple Quantum Well Plasmon Source

Recently, many researches are reported on using germanium in silicon-based lasers but acquiring this potential for a plasmonic nanolaser may also be important for development of silicon-compatible plasmon sources. In this paper, a custom-shaped nanocavity plasmon source based on highly doped tensile-strained germanium/silicon-germanium multiple quantum well gain medium is introduced and theoretically investigated. We have used a semi-classical macroscopic rate equation model for calculation of the output performance characteristics. Also, modal analysis has been done based on FDTD method. The proposed nanolaser has a tiny footprint of 0.1225 μm2, possible room temperature performance, and fabrication process based on a silicon substrate. The output performance of the nanolaser structure as estimated is noticeable and the calculated results, using some previously reported experimental data and redundant software double checking, show acceptable compatibility. In 1550-nm output wavelength, it provides 15.6 mW output power in the 21-mA threshold current and 600 μW in 1-mA pump current, while maintaining its performance in a wide spectral bandwidth about 2 THz. It also can be electrically modulated by the pump current up to 3 GHz. This remarkable performance is achieved, thanks to the high Purcell factor of the parabolically notched nanocavity of about 700 and its high quality factor of about 58.