Optical microcavities confine molecular luminescence and transfer it to a far longer distance than the conventional Förster resonant energy transfer process. Such cavity‐mediated energy transfer is advantageous for use in optical circuitry. However, to realize all‐organic optical circuits, optical gate operation with organic materials is indispensable. Here, all‐organic optical gates consisting of polymer whispering gallery mode (WGM) resonators that work as the optical source, drain, and gate, which are interconnected with polymer microfiber, are demonstrated. Photoirradiation of the source sphere, as an optical input, triggers the blue fluorescence that transmits to the gate sphere through the fiber. The fiber interconnection enhances both the light confinement efficiency in the individual spheres and the light transmission efficiency between distant spheres. The gate sphere contains photoisomerizable fluorescent dye that converts, in its closed state, the blue emission into green light, which is again transmitted to the drain sphere through the fiber and lets the sphere emit red light as an output. This optical cascade is switched on and off upon photoisomerization of the dye in the gate sphere. Furthermore, an energy cascade equipped with two gate spheres works as an OR‐type logic gate, demonstrating potential utility for the future all‐organic and all‐optical integrated devices.

Optical resonators work as precise physical and chemical sensors. Here, we assemble a whispering gallery mode resonator from a natural polymer, fibroin protein, and successfully observe its catalytic degradation reaction...