Far-field characteristics of random lasers

We report on experimental observation of the far-field intensity and mode distributions of random lasers. Laser emission from highly disordered semiconductor polycrystalline thin films could be observed in all directions. The angle dependence of the laser output from the edge of the film is different from that of the laser emission scattered out of the surface of the film. More lasing modes are observed from the surface of the film than from the edge of the film, A qualitative explanation of the experimental results are presented based on the laser cavities formed by optical scattering being located in the plane of the films. [S0163-1829(99)04623-8].