Signatures of periodicity and randomness in the angular emission profile of a 2-D on-average periodic optofluidic random laser.

Angle-dependent emission from a dye infiltrated 2-D on-average periodic structured optofluidic random laser is studied. Distinct signatures of periodicity and randomness are observed in the angle-resolved emission spectra of the device. Emission patterns composed of concentric ellipses are observed on transverse excitation of the device, attributed to the in-plane diffraction of light by a 2-D square lattice. The effect of randomness on the emission spectra is demonstrated by a highly resolved angle-dependent spectral scan of a single diffraction fringe. Finally, we conclude that the randomness in the size of the scatterers resolves the random lasing modes angularly.