Lasing from a Forster transfer fluorescent dye couple dissolved in a chiral nematic liquid crystal

Forster exciton transfer from a 'sensitizer' to an 'emitter' dye allows for the decoupling of the excitation and emission processes in dye lasers. Here, we report on the lasing from a Forster transfer couple dissolved in an unconventional, mirrorless resonator; namely, a chiral nematic liquid crystal (CNLC). We found optically pumped lasing at a threshold as low as 2.1 J m(-2). We also demonstrate simultaneous lasing at two widely separated wavelengths.