Wavelength Tunable Plasmonic Lasers Based on Intrinsic Self-Absorption of Gain Material

Multicolor plasmonic nanowire lasers enable below diffraction-limit directional optical waveguiding and amplification vital to the development of next generation compact on-chip optical communications, super-resolution imaging, display technologies, and so on. However, progress in developing these compact lasers for different wavelengths is severely curtailed by the few complex fabrication methods available. In this work, we demonstrate wavelength-tunable plasmonic nanowire lasers by leveraging the intrinsic optical self-absorption of the gain medium. The plasmonic lasing wavelength is tunable from 465 to 491 nm by simply adjusting the nanowire length, that is, by approximately 76% over the interval width of the emission spectrum. The Purcell factor of plasmonic nanowire cavity decreases with increasing nanowire length; while the propagation loss increases from 1020 to 8354 cm^-1 with decreasing nanowire diameter, exhibiting a plasmonic-photonic mode transition at diameters around 120-150 nm. Importantly, our findings advance the fundamental understanding and provide a new approach for engineering wavelength tunable plasmonic lasers.