Abstract
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.
Highlights
Organic semiconductors enable the fabrication of a range of lightweight and mechanically flexible optoelectronic devices
We show how membrane lasers that were designed to produce a well-defined and unique lasing spectrum can be used as counterfeit-resilient, barcode-type security labels on bank notes
To produce transferable and thin membrane lasers, we developed a water-based lift-off technique that releases the final device from a carrier substrate at the end of the fabrication process (Fig. 1a)
Summary
Organic semiconductors enable the fabrication of a range of lightweight and mechanically flexible optoelectronic devices. Pumped organic solid-state lasers have gained widespread attention as coherent light sources that are easy to fabricate, have emission tunable across the whole visible range, and are potentially disposable and biocompatible[1,2,3,4,5,6,7,8]. There have been examples of flexible DFB designs[21,22,23,24,25] These use substrates or matrices of macroscopic thickness, or require metal oxide intermediate layers and femtosecond pumping schemes. We show how membrane lasers that were designed to produce a well-defined and unique lasing spectrum can be used as counterfeit-resilient, barcode-type security labels on bank notes. Due to the low threshold of our membrane laser, a similar configuration is expected to be safe to use in the human eye, e.g. to complement biometric iris recognition
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