Optically coupled bilayered disordered system for spatially controllable dual band random lasing and random number generation

Random lasers (RLs) are emerging as a new family of partially coherent light sources with favorable characteristics for specific applications. The inherent role of disorder in RL phenomenon offers a natural route for the generation of random numbers. Here, we use the strong scattering and high surface-to-volume ratio of ZnO microcabbages (ZnOMCs) to achieve a low-threshold RL from different organic dyes. On these grounds, we build a dual-emitting solid-state RL where two polymer films, embedding ZnOMCs mixed with two different dyes, are optically coupled to each other in a layered configuration. The combined effect of saturable absorption and energy transfer between the two films allows us to achieve tunable RL emission, with spectral characteristics that can be simply controlled by moving the position of the focal point along the depth of the lasing device. Furthermore, we show that the low correlation between the two emitting bands can be exploited for unclonable random binary number generation, paving the way for using this solid-state RL in encryption and secure communication technologies.