Integrated Optical Investigation of Two Light-Sensitive Proteins

Integrated optics is one of the most intensively investigated fields when working on alternative methods to overcome the disadvantages of integrated electronics. Besides inorganic 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 state-of-the-art photonic integration technology is ready to provide the passive elements of integrated optical circuits. The bottle-neck in integrated optics is to find a proper nonlinear optical material that is supposed to be the cladding medium in waveguide-based photonic applications, performing light-controlled active functions. Based on our earlier results, here we present the experimental demonstration of subpicosecond photonic switching with an alternative approach, where the active role is performed by a biological material, the chromoprotein bacteriorhodopsin. Moreover, measurements of the light-induced refractive index change performed on a dried film of the Photoactive Yellow Protein are also presented. Our findings show that these photochromic pigments can be promising candidates as active nonlinear optical materials for all-optical data processing in future biophotonic applications. These results may serve as a basis for the future realization of protein-based integrated optical devices that can eventually lead to a conceptual revolution in the development of telecommunication technologies.