Transient diffraction efficiency of a D96N mutant bacteriorhodopsin film

A three-laser-beam technique is developed to study the transient diffraction efficiency of M-state dynamic phase holograms in a D96N mutant bacteriorhodopsin film (BR). A CW beam from 532 nm doubled Nd: YAD laser is used to pump BR molecules from B-state to photoexcited M-state. Then the M-state absorption laser 413-nm wavelength from a Krypton Ion laser is used to write holographic gratings in the excited M-state. The writing process also depletes M-molar concentrations. This process offers the advantages of better modulation and faster response. The reading is done with a 680 nm laser, which is far away from the absorption bands to ensure a negligible erasing effect on the gratings written in the film, resulting a pure phase hologram with high efficiency. A maximized transient peak diffraction efficiency approaches a saturated value when the ratio of write to pump intensity is approximately unity.