Subpicosecond Photonic Switching Based on Bacteriorhodopsin

Abstract

The continuous growth of internet traffic represents a serious demand for significant improvement both in capacity and speed of data trafficking. All-optical data processing is generally considered to be the most promising approach to achieve these goals. The state-of-the-art photonic integration technology is ready to provide the passive elements of the optical integrated circuits. The bottle-neck is a proper nonlinear optical material in waveguide-based integrated optical circuits that provide the light-controlled active functions. Several inorganic and organic materials have been suggested for this special application, however, none of them is considered to be the optimal solution. Here we present a subpicosecond photonic switch where the active role is performed by the chromoprotein bacteriorhodopsin. The changes in the refractive index that accompany the steps of the photocycle of bacteriorhodopsin are used for all optical switching in appropriate integrated optical devices. We use grating coupled planar waveguides and the coupling is modulated by the light induced refractive index changes of bacteriorhodopsin. The switching is demonstrated in ultrafast pump-probe experiments. Different transitions of the photocycle are explored for switching applications. We show that by using the bR to I transition subpicosecond switching can be readily achieved. The approach may serve as a basis for the realization of protein-based integrated optical devices, eventually leading to a conceptual revolution in telecommunications technologies.