Statistical fluctuations of coherent and incoherent intensity in random lasers with nonresonant feedback

We report on intensity fluctuations of a coherent random laser based on incoherent feedback via nonresonant multiple scattering. We quantify the spectral line shape fluctuations in terms of correlations of an individual spectrum with the ensemble-averaged spectrum, which infers the signature of the gain profile of the medium. These correlations are studied in relation to the intensity of the highest coherent modes. We evaluate the distribution of the ratio of the coherent and incoherent fractions in the emission, after independently assessing their statistics. Finally, these intensity fluctuations are graphically represented in a single scatter plot, the centroid of which can be used as a characterization parameter for the laser.