On chip random lasing performance of the acceptor dye in a specially designed linear and zig zag array of microdroplets with intrinsic disorder.

We demonstrate high-quality on chip random lasing of the acceptor dye using a specially designed dynamic linear array of microdroplets with unconventional shapes that do not support the whispering gallery modes. The intrinsic disorder in the droplet array consequent to its dynamic nature is utilized in achieving the randomness in the lasing emission without deliberately adding the disorder as in ordinary random laser systems. The novelty of the generated structure is illustrated by comparing its emission characteristics with two other arrays made of microspheres and microtriangular droplets arranged in a zig zag fashion. We show that only the linear array of microdroplets supports lasing in the acceptor emission. The design of the array structure allows to further reduce the lasing threshold drastically either by incorporating the radiative energy transfer or by tuning the number of acceptor dye molecules. The highly directional, well-controlled, and intense emission of weakly emitting dye generated on chip without the aid of conventional methods opens up a new scheme of random lasing generation mediated by microdroplets.

Synthesis of silver nanoparticles in poly(vinyl alcohol) matrix in solution and thin films through laser irradiation.

Here we communicate our experimental results on the synthesis of silver nanoparticles in solution and thin films using silver nitrate and poly vinyl alcohol (PVA) mixture at different concentrations and different laser irradiations. Detailed studies were carried out by varying pulse width, wavelength, exposure time, and energy of the laser. Formation of nanoparticles was confirmed through color change from transparent to yellow. Irradiated solutions and thin films at different concentrations showed plasmon peak in the absorption spectra. Formation of different sized nanoparticles at different energies with peak shift is observed. Transmission electron microscope (TEM) results confirmed the formation of nanoparticles with size of the particles varying from 2 to 200 nm. Formation of silver nanoparticles with hexagonal and different shapes were observed in particular with 355 nm laser irradiation. Influence of wavelength, pulse width, exposure time, and energy in the synthesis of silver nanoparticles is highlighted. Electron diffraction patten of a single nanoparticle in TEM showed polycrystallinity with cubic nature for the silver nanoparticles prepared. We also compared the linear and nonlinear absorption properties of the freshly prepared nanoparticles with nanoparticles solution left in a shelf for a long period of time.