Gain-Based mechanism for pH Sensing Based on Random Lasing

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