Statistics of randomized plasmonic lattice lasers
We study lasing in randomized lattices of silver particles in a dye-doped waveguide. We set out to answer a basic question, triggered by earlier observations of distributed feedback lasing in 2D periodic plasmonic particle lattices: how much order do you need to obtain lasing? We start from a diffractive 2D square lattice of silver nanoparticles with a pitch that satisfies the second-order Bragg diffraction condition at the emission wavelength of the dye. By randomly removing particles and by displacing particles we increase disorder. We observe that lasing at the second-order Bragg diffraction condition is very robust, with lasing even persisting when 99% of particles are removed. Above a certain amount of disorder new features appear in the spectrum as well as in the Fourier image that are due to random lasing. We classify Fourier space output on the basis of structure factor calculations. In addition we apply speckle intensity statistics analysis to real-space fluorescence images and introduce a new method to differentiate between spontaneous emission and lasing emission.