Theoretical Simulation On Photochromism And Photoanisotropy Of Bacteriorhodopsin And Its Applications

Bacteriorhodopsin(BR) is well-known as a biomolecular photochromic material for its unique optical and photoelectric properties. It is one of the important materials in the field of optical storage, optical signal processing, and photoelectric functional materials. Recently, the incorporation of genetic technology infuses new vigor into the application research based on BR. Focusing on the optical properties and applications of BR film, the author mainly completed the following works:1. The photochromic properties of BR film upon illumination of single- and two-beam of excitation are studied. Based on the two-state photochromic model, the first-order approximation formulae and numerical calculation method were established. Using the two methods, we simulated the photochromic kinetic process and the saturation absorption properties of BR film excited by single- and two-beam. The theoretical calculation results and the experimental results showed consistency when the effect of the intensity distribution of the beam spot was taken into account. The theoretical and experimental results demonstrated that the photochromic kinetic process of BR is intensity-dependent. Besides, the transmission of red light can be restrained by the violet light.2. The photoinduced anisotropy of BR film is studied. The relation between photoinduced anisotropy (dichroism and birefringence) and the BR molecule population distribution in the BR film was obtained by the two-state photochromic model. The pump-probe method for measuring the photoinduced anisotropy of BR by was elucidated and the dependence of photoinduced anisotropy on the distribution of the population of BR molecule was obtained. The kinetics of photoinduced anisotropy of B-type, M-type and B-M type are calculated theoretically after considering the relation between the transmittance of P-BR-A (polarizer-BR-analyzer) system and the BR molecule population distribution, the theoretical calculation results and the experimental results are consistent. The effect of intensity of exciting beam and detecting beam on the angle of polarization rotation is theoretically calculated. The theoretical and experimental results demonstrated that compared with single pumping beam, duel-wavelength linearly polarized pumping beams can obviously change the photoinduced anisotropy. The perpendicularly polarized pair can remarkably enhance the anisotropy, while the parallelly polarized pair can restrain the anisotropy.3. The effect of recording intensity on diffraction efficiency of holographic grating is studied experimentally and theoretically. By taking the effect of the saturation absorption and the scattering and reflecting lights from the BR film on grating contrast-ratio of the hologram into account, the change of the peak diffraction efficiency of hologram with the recording intensity was explained.4. The characteristics of the polarization holographic grating recorded in BR film were studied. The Jones matrix of holographic grating recorded by the parallel linearly polarized recording beams and the orthogonal linearly polarized recording beams are found based on the simplified two-state photochromic model and the selective absorption of BR molecule on the polarized excitation light. The polarization state and the diffraction efficiency of first-order diffraction wave were analyzed, for the grating recorded by the parallel linearly polarized recording beams and the orthogonal linearly polarized recording beams. The effect of intensity and polarization orientation of auxiliary violet light on the kinetics of diffraction efficiency was studied experimentally and theoretically. The results demonstrated that at the low recording light intensity, the steady diffraction efficiency is increased and the peak diffraction efficiency is suppressed by the violet light. For intense intensity of recording light, the steady diffraction efficiency and the peak diffraction efficiency can be both enhanced by the auxiliary violet light.5. Application of BR film in phase-shifting interferometry is studied. A phase-shifting interferometer based on the photoinduced anisotropy of BR film is presented theoretically. The interference patterns are obtained from the phase-shifting interferometer, the profile of the phase objects are reconstructed from the wrapped phase map with the method of phase gradient integration.6. The optical information processing was realized with the BR film. Based on the properties of photoinduced anisotropy of BR film, a scheme of all-optical logic gates is presented theoretically and experimentally. The all-optical logic AND, OR, XOR etc gate operations have been demonstrated experimentally. In addition, a series of applications such as all-optical switching, image display and spatial filtering were carried out.