Low threshold and wavelength tunable SPASER based on plasmonic coupled nanostructure

Abstract

We propose a low threshold and wavelength tunable plasmonic coupled nanolaser based on a plasmonic coupling between Au nanosphere and Au film. By the finite-element method, we investigate the optical properties of the plasmonic coupled nanolaser with different nanosphere diameters and gap distances between Au nanosphere and Au film. The optical cross section of the plasmonic nanolaser based on the coupled nanostructure can be 60 times larger than that based on an independent Au nanosphere. And the corresponding gain threshold of the plasmonic coupled nanolaser is only 35% of that of the nanolaser with the independent Au nanosphere. This is attributed to that the coupled nanostructure exhibits a stronger electric field and optical intensity than the independent Au nanosphere, it can more effectively improve gain to compensate for metal loss. In addition, the plasmonic coupled nanolaser also exhibits a wavelength tunability in a wide spectral range by controlling the Au nanosphere diameter and gap distance between Au nanoparticle and Au film. This work can provide us an effective way to develop the on-chip application of nanolaser.