LAUSR

We observe lasing emission from an organic microcavity structure at room temperature with a sunflower-like pattern closely resembling Laguerre-Gauss modes. Simultaneously, measured angle-resolved emission spectra below and above the lasing threshold demonstrate the coexistence of discrete modes, confined in a doughnut-shaped potential, and continuously propagating modes with parabolic dispersion. This phenomenon can be explained by a spatially and intensity-dependent change in the refractive index of the organic material, induced by nonlinearity associated with the bleaching of the dye layer at high excitation intensities. A theoretical model shows that Laguerre-Gauss modes well describe the experimental observation.