All-optical switching with bacteriorhodopsin

All-optical, mirrorless switching is demonstrated with bacteriorhodopsin (bR) film using a very simple geometry. A low-power, 532 nm laser beam modulates the transmission of a cw laser beam at 635 nm, a wavelength that corresponds to peak absorption of the O-excited state in the bR photocycle. The switching contrast depends on the pulse width and average power of the modulating laser. Varying the pulse width and frequency of the modulating laser controls the phase of the switching characteristics. Simulations based on a rate equation approach consider a six-state model of the bR photocycle that successfully reproduce the experimental results