Silk-based biocompatible random lasing

Random lasing exploits multiple scattering in an active disordered system in order to promote light amplification [1, 2]. Here we propose random lasing as a mechanism for sensing, capable of probing subtle changes in chemical environment due to the intrinsic non-linear response as well as the large spectral purity [3]. We report a biocompatible self-assembled random laser, made entirely of doped silk [4], showing clear threshold behaviour and spectral narrowing. We show that with a simple self-assembly process the porous silk matrix can be incorporated with different dyes and casted in a free-standing inverse photonic glass [5] with designed collective scattering Mie resonances [6]. This acts as a nonlinear sensor that switches off lasing for high pH values. The combination of a natural biopolymer and random lasing offers the opportunity for integration of a laser within living tissue, opening a new path at the interface between nanophotonics and medicine.