An exciton-polariton laser based on biologically produced fluorescent protein

Under adequate conditions, cavity-polaritons form a macroscopic coherent quantum state, known as polariton condensate (PC). Compared to Wannier-Mott polaritons in inorganic semiconductors, the localized Frenkel polaritons in organic emitter materials show weaker interaction with each other but stronger coupling to light, which recently enabled the first realization of a PC at room temperature. However, this required ultrafast optical pumping which limits the applications of organic PCs. Here, we demonstrate room-temperature PCs of cavity-polaritons in simple laminated microcavities filled with the biologically produced enhanced green fluorescent protein (eGFP). The unique molecular structure of eGFP prevents exciton annihilation even at high excitation densities, thus facilitating PCs under conventional nanosecond pumping. Condensation is clearly evidenced by a distinct threshold, an interaction-induced blueshift of the condensate, long-range coherence and the presence of a second threshold at higher excitation density which is associated with the onset of photon lasing.