Soret reverse saturable absorption of graphene oxide and its application in random lasers

In the past, carbon-based materials have shown both saturable and reverse saturable absorption, and most recently among them, the optical limiting behavior of graphene and graphene oxide caused by nonlinear scattering or fast nonlinear absorption effects, which have been consolidated. Here, we demonstrate the thermal diffusion of graphene oxide flakes in dispersion as a new nonlinear effect not yet explored. We show a damping of 50% in the transmission, and we follow its dynamics in time. Moreover, this nonlinearity, known as the Soret effect, is used to limit the emission from a disordered random laser reaching a decrease of about 90% of the emitted peak intensity without a substantial alteration of the cavity efficiency.