High-speed integrated optical logic based on the protein bacteriorhodopsin

The principle of all-optical logical operations utilizing the unique nonlinear optical properties of a protein was demonstrated by a logic gate constructed from an integrated optical Mach–Zehnder interferometer as a passive structure, covered by a bacteriorhodopsin (bR) adlayer as the active element. Logical operations were based on a reversible change of the refractive index of the bR adlayer over one or both arms of the interferometer. Depending on the operating point of the interferometer, we demonstrated binary and ternary logical modes of operation. Using an ultrafast transition of the bR photocycle (BR-K), we achieved high-speed (nanosecond) logical switching. This is the fastest operation of a protein-based integrated optical logic gate that has been demonstrated so far. The results are expected to have important implications for finding novel, alternative solutions in all-optical data processing research. ► An all-optical, nanosecond logical switch was realized. ► The active material in the integrated optical device was the protein bacteriorhodopsin. ► The device (a comparator) worked in the ternary logic mode. ► The results demonstrate the applicability of a biomaterial in information technology.