Multi‐Wavelength Plasmonic Nanolasers with Giant Gain‐Bandwidth Broadening Through Enhanced Fermi Filling

Tunable or multi‐wavelength lasing in a wide wavelength range is crucial for applications including multi‐band optical communication, displays, and lighting, but remains challenging due to the limited gain bandwidth of a given semiconductor. Traditional methods for gain broadening, such as Fermi filling at high injection levels, are constrained by the high pump power required and associated self‐heating effects. Here, a significantly enhanced gain bandwidth in a plasmonic nanolaser is demonstrated, taking advantage of the small sizes of such nanolasers with lateral dimensions below the diffusion length. This allows extremely high carrier density buildup and leads to a gain‐bandwidth as large as 400 nm (from 1200 to 1600 nm), covering all the optical communication bands. Combined with the low‐threshold silver‐cup plasmonic nanocavities, lasing spanning over 350 nm at room temperature is observed, nearly twice that of the multi‐wavelength or tunable lasers reported so far. In addition, the required pump energy is reduced to ≈10 fJ, or at least an order of magnitude lower than previous demonstrations. Such nanolasers are potential candidate for light sources for on‐chip applications due to their small footprint, low threshold, and broad wavelength range of operation.