Gain-Based mechanism for pH Sensing Based on Random Lasing

Here, we investigate the mechanism of a random-lasing-based sensor which shows pH sensitivityexceeding by 2 orders of magnitude that of a conventional fluorescence sensor. We explain the sensingmechanism as related to gain modifications and lasing-threshold nonlinearities. A dispersive diffusive lasingtheory matches the experimental results well, and it allows us to predict the optimal sensing conditions and amaximal sensitivity as large as 200 times that of an identical fluorescence-based sensor. The lack of complexalignment and the high sensitivity make this mechanism promising for future biosensing applications.