Huge
spectral coverage of random lasing throughout the visible
up to the infrared range is achieved with star-shaped gold nanoparticles
(“nanostars”). As intrinsically broadband scattering
centers, the nanostars are suspended in solutions of various laser
dyes, forming randomly arranged resonators which support coherent
laser modes. The narrow emission line widths of 0.13 nm or below suggest
that gold nanostars provide an efficient coherent feedback for random
lasers over an extensive range of wavelengths, all together spanning
almost a full optical octave from yellow to infrared.
Here,
we report that hybrid multilayered plasmonic nanostars can
be universally used as feedback agents for coherent random lasing
in polar or nonpolar solutions containing gain material. We show that
silver-enhancement of gold nanostars reduces the pumping threshold
for coherent random lasing substantially for both a typical dye (R6G)
and a typical fluorescent polymer (MEH-PPV). Further, we reveal that
the lasing intensity and pumping threshold of random lasers based
on silver-enhanced gold nanostars are not influenced by the silica
coating, in contrast to gold nanostar-based random lasers, where silica-coated
gold nanostars support only amplified spontaneous emission but no
coherent random lasing.
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