  Linewidth-tunable lasers have great application requirements in the fields of
high-resolution spectroscopy, optical communications and other industry and
scientific research. Here, the switchable plasmonic scattering of the metal
particles with plenty of nanogaps is proposed as an effective method to achieve
linewidth-tunable random lasers. By using the nonlinear optical effect of the
environment medium, the metal particles demonstrate the transition from local
scattering of nanogaps with high spatial frequency to traditional Mie
scattering free from detail information with increasing the pump power density.
Based on these two scattering processes, random lasers can be continuously
driven from a narrow-linewidth configuration exhibiting nanogap effect
dominated resonances to a broad-linewidth regime of collectively coupling
oscillating among nanowires (or nanoflowers), demonstrating the dynamic range
of linewidth exceeds two orders of magnitude. This phenomenon may provide a
platform for further studying of the conclusive mechanism of random lasing and
supply a new approach to tune the linewidth of random lasers for further
applications in high-illumination imaging and biology detection.
