Top‐Layer Resonator Organic Distributed Feedback Laser for Label‐Free Refractive Index Sensing

Abstract Surface‐emitting organic distributed feedback (DFB) lasers are attractive devices for label‐free sensing applications. Of particular interest for cost‐reduction purposes are devices in which both active material and resonator are based on solution‐processable polymeric materials. Here, the capability for label‐free refractive index sensing of DFB devices consisting of top‐layer resonators (1D relief gratings) of dichromated gelatin layers is reported, deposited on top of active films of polystyrene doped with perylene orange. The devices show successful operation for both transversal electric and transversal magnetic modes, with a larger sensor sensibility for the latter (Sb = 38 nm RIU⁻¹). The overall device operation (emission laser wavelength, laser threshold in addition to the sensitivity) has been optimized through the adjustment of the active film thickness and the grating period. This is possible thanks to the versatility offered by the holographic procedure used to fabricate the resonator, and to the top‐layer resonator geometry. Remarkably, the fact that the resonator is based on gelatin (a food‐grade biopolymer), offers great potential for the development of wearable and bio‐compatible sensing applications.