LAUSR

Optical carrier incubation can effectively alter the electron transport properties of semiconductors; thus, optical switching of the plasmonic response of the semiconductor enables the ultrafast manipulation of the light at the nanoscale. Semiconductor nanostructures are promising platforms in on‐chip high‐speed plasmonic devices, owing to their high photoinduced electron injection efficiency at sub‐picosecond and compatibility with contemporary semiconductor technologies. The pure single crystalline InSb nanowires are promising plasmonic materials in the mid‐infrared region due to their high electron mobility and small electron effective mass. Here, the pump–probe nanoscopy is utilized to investigate the pump fluence dependency and the dynamics of the non‐equilibrium plasmons in the InSb nanowires. The InSb plasmon is successfully switched by injecting the photoinduced electrons and the practical tuning of the plasmon frequency to one octave is shown by increasing the pump fluence from 0 to 90 µJ cm−2. The density of the photoinduced electrons in InSb nanowires is 18.8 × 1018 cm−3 with pump fluence as low as 90 µJ cm−2. The high electron mobility of the InSb supports the low‐loss plasmon with a damping rate of ≈200 cm−1. The InSb nanowires’ excellent plasmonic properties ensure that they are a promising platform for upcoming high‐speed mid‐infrared plasmonic materials for informatic devices.