High Speed All Optical Logic Operations Utilizing the Protein Bacteriorhodopsin

Abstract

In data-processing applications requiring high speed and wide bandwidth, photonic devices - where logic operations are processed on an all-optical basis - represent a promising alternative of their electronic counterparts. Besides in/organic active optical crystals, dyes and polymers, molecules of biological origin with suitable nonlinear optical properties can also find applications in integrated optical - biophotonic - devices.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.