Microcavities filled with biologically produced green fluorescent protein show polariton condensation at room temperature.

Traditional low-molecular weight colorants that are widely applied in textile coloration, for printing purposes and nonlinear optics, now afford bulk heterojunction solar cells in combination with soluble C₆₀fullerene derivative PCBM with power conversion efficiencies up to 1.7% under standard solar radiation.

Organic semiconductors enable the fabrication of a range of lightweight and mechanically flexible optoelectronic devices. Most organic semiconductor lasers, however, have remained rigid until now, predominantly due to the need for a support substrate. Here, we use a simple fabrication process to make membrane-based, substrate-less and extremely thin (<500 nm) organic distributed feedback lasers that offer ultralow-weight (m/A<0.5 gm⁻²) and excellent mechanical flexibility. We show operation of the lasers as free-standing membranes and transfer them onto other substrates, e.g. a banknote, where the unique lasing spectrum is readily read out and used as security feature. The pump thresholds and emission intensity of our membrane lasers are well within the permissible exposures for ocular safety and we demonstrate integration on contact lenses as wearable security tags.