Metal–Semiconductor Square Nanocavity and Light Extraction

We propose a design of metal-semiconductor square nanocavity on silicon that could be used for on-chip nanolaser application, together with an efficient mechanism of light extraction, which is important for practical application. The analysis of the spatial mode for the square nanocavity is carried out, and hybrid plasmonic-photonic mode profile is observed in the cavity. Optimized design of the square cavity gives a mode volume of 0.96(λ/2n)
³
and resonant wavelength of 1474 nm when the side length is 600 nm. The outcoupling mechanism for the nanocavity is based on a direct-joint plasmonic waveguide. The effects of width, position, and angle of the output plasmonic waveguide on the outcoupling efficiency are studied, and the difference in cavity mode with respect to circular nanocavity has contributed to the different outcoupling performances. The analysis shows that the output coupling efficiency can be tuned up to 60% by varying these parameters, and this offers an output coupling mechanism with great flexibility for ultra-compact on-chip light source.