Strong coupling in fully tunable microcavities filled with biologically-produced fluorescent proteins

Strong coupling between cavity photons and excited states of biologically produced recombinant fluorescent proteins in fully tunable optical microcavities is demonstrated. Natural thickness and concentration gradients in blends of two different proteins allow precise adjustment of the spectral position of polariton states and of the effective coupling strength, thus providing control of the photonic and excitonic components of the system