Optical Gain Switching by Thermo-Responsive Light-Emitting Nanofibers through Moisture Sorption Swelling

摘要

The development of intelligent photonic systems made of stimuli-responsivematerials, i.e., with features tunable and switchable by environmental signals,is gaining increasing attention. Here, the study reports on switchable opticalgain based on complex arrays of nanofibers made of thermo-responsivepoly(2-n-propyl-2-oxazoline), incorporating a blue-emitting chromophore. Thefluorescent component endows the nanofibers with optical gain in addition tothe moisture absorption capability of the polymer. Light amplification is foundwith temperature- and humidity-dependent excitation threshold. Thethreshold value is halved close to the polymer cloud point temperature,enabling reversible switching of the emission intensity upon temperaturechange. Waveguiding analysis by back-focal plane imaging on individual fibersallows the switching mechanisms to be rationalized, in terms of moisturesorption swelling-induced morphological changes. These responsivelight-emitting nanofibers may find application in a novel class of lasers withdynamically-controlled properties, environmentally-switchableoptoelectronics, and smart sensors.