Bacteriorhodopsin based photonic logic gate and its applications to grey level image subtraction

A novel photonic logic gate model is presented based on a thin film containing the light-controlled absorption of the biological photochrome bacteriorhodopsin (BR). Under illumination by two beams of wavelength around 568 and 412 nm, respectively, there exists a threshold intensity around which the transmission of the two beams are modulated in a complementary fashion. The local transmission within the film depends on the ratio of the forward and backward photoreaction rates which can be controlled by either light illumination or material modification. An example demonstrating the logic operation of the device is given for a possible practical application of an incoherent two-dimensional multiple grey level image subtraction.