Random lasing using laser generated and modified silver nanoparticles

The authors report incoherent random laser action in systems where the optical feedback is provided by multiple scattering generated by different classes of silver nanoparticles in the colloidal state, having plasmon resonances at different frequencies. They found improved performance of triangular silver nanoplates as compared to nanospheres, with a threshold as low as 1 mJ/cm2 and a 5 times lower optimal silver concentration, due to plasmonic enhancement effects and tuning of the plasmon resonance. The nanoparticles were also tested for stability against illumination by the pump laser, as the onset of pulsed laser melting is comparable to random laser threshold in terms of pump fluence, severely limiting the range of operation of nanoparticles with main plasmon resonance close to the pump wavelength. The optimal approach to choose plasmonic nanoparticles for random lasing must, therefore, take the stability aspect into serious consideration as well as the plasmonic enhancement of random lasing.