Effect of external feedback on lasing in random media

Abstract

We have studied the effect of external feedback on random laser action in ZnO polycrystalline thin films. Reinjection of light into scattering-formed cavities strongly influences modes, intensity, and threshold of random lasers. We have compared the effect of external feedback from the side of the film and that from the film surface. Our study opens the possibility of controlling random laser frequencies by external feedback.