Solid-state random microlasers fabricated via femtosecond laser writing

Here we demonstrate resonant random lasing in Rhodamine B-doped polymeric microstructures fabricated by means of femtosecond laser writing via two-photon polymerization. To the best of our knowledge, this is the first demonstration of random lasing action in on-chip microdevices. Their feedback mechanism relies on diffuse reflections at the structure sidewall surfaces, which is known as spatially localized feedback since the scattering centers lie over the edges of the gain medium. By exciting the structures with a pulsed laser at 532 nm, a multimode emission with randomly distributed narrow peaks was observed, in accordance with the random nature of the feedback mechanism. Interestingly, their lasing threshold was found to be on the order of tens of nanojoules, which is comparable to what had been achieved for usual microcavities, thereby demonstrating the potentiality of these devices as solid-state lasers for integrated optics applications.