Photonic spectral modulation in bacteriorhodopsin molecules and optimization of signal wavelength

Abstract

In general, in excited-state absorption (ESA) based all-optical light modulator, maximum signal intensity modulation is achieved at the wavelength corresponding to maximum excited to ground state absorption cross-section ratio. However, theoretical analysis of photonic spectral modulation of broadband signal beam based on ESA in bacteriorhodopsin (BR) provides counterintuitive interesting results in the signal wavelength region 460–700nm. It is shown that the signal modulation is enhanced significantly at some particular wavelength values (optimum signal wavelength). Optimum signal wavelength in the region 450–700nm, varies with modulating intensity, and does not correspond to the peak absorption wavelength of the longer lived intermediate states. Present analysis is very useful in designing ESA based power efficient photonic devices.