Here we show lasing from a monolayer VCSEL using a single molecule thick film of amphiphilic fluorescent dye¹ as the gain layer. Vertical Cavity Surface Emitting Lasers (VCSELs), in which lasing occurs perpendicular to the device plane, are critical for telecommunications and large-scale photonics integration, however strong optical self-absorption and low fluorescence quantum yields²  have thus far prevented coherent emission from a monolayer microcavity device. This is the first demonstration of lasing using organic monolayer and the first demonstration of lasing using any monolayer in planar microcavity configuration. The monolayer was assembled via Langmuir-Blodgett deposition and situated between two highly reflective dielectric mirrors. Lasing was observed upon excitation by nanosecond pulses at 4.4 μJ/cm² when 5% of the fluorescent molecules were excited. Lasing was accompanied by a change in slope of the output intensity curve, the appearance of polarized emission, and a narrow spectral line above the threshold. We observed that the lasing threshold depends sensitively on normalized differential gain and less on the emission lifetime as result of Purcell effect. Monolayer VCSELs may pave the way for new photonic devices in which the relative phase between emitting excitons can be controlled. Recent research shows that negative effects associated with electrical pumping are weaker when a small volume of organic material is excited³ and thus current work can be another step towards electrically pumped organic lasers.

1. Aviv, H., Harazi, S., Schiff, D., Ramon, Y., & Tischler, Y. R. (2014). Synthesis of an amphiphilic rhodamine derivative and characterization of its solution and thin film properties. Thin Solid Films, 564, 86-91.

2. Green, Adam P., and Alastair R. Buckley. "Solid state concentration quenching of organic fluorophores in PMMA." Physical Chemistry Chemical Physics 17.2 (2015): 1435-1440.

3. Hayashi, Kyohei, et al. "Suppression of roll-off characteristics of organic light-emitting diodes by narrowing current injection/transport area to 50 nm." Applied Physics Letters 106.9 (2015): 093301.