Explaining the mechanism of random lasing based sensing

Here we report a random lasing based sensor which shows pH sensitivity exceeding by 2-orders of magnitude that of a conventional fluorescence sensor. We explain the sensing mechanism as related to gain modifications and lasing threshold nonlinearities. A dispersive diffusive lasing theory matches well the experimental results, and allow us to predict the optimal sensing conditions and a maximal sensitivity as large as 200 times that of an identical fluorescence-based sensor. The simplicity of operation and high sensitivity make it promising for future biosensing applications.