Bacteriorhodopsin Films Research Articles

Upper limits of dielectric permittivity modulation in bacteriorhodopsin films

A theoretical study of light-induced modulation of the dielectric permittivity in bacteriorhodopsin films has been done (including B--> M and B --> Q transitions). Analysis of dielectric permittivity modulation enables us to determine the fundamental limits of BR to be used in a holographic data storage system, together with the optimum experimental and material conditions. In order to carry out this analysis, the macroscopic dielectric permittivity was related to the microscopic polarizability of the three states of BR considered (B, M and Q). This parameter was calculated using a modelization procedure that includes the effect of ASP85, TRP86, and TYR185 amino acid residues (the B3LYP/6-31+ G(*) method was used for the calculations). Good concordance between theoretical calculations and experimental data was found for the linear optical properties (absorption wavelength, transition dipole moment, and dielectric permittivity modulation). The theoretical upper limits of Deltaepsilson at 750 nm (far from the resonance of the molecule) in a randomly oriented material are about 0.01 and 0.012 for B--> M and B--> Q transitions, respectively. The values of Deltaepsilon obtained were used to simulate diffraction efficiencies (eta) of a volume phase hologram recorded in a BR film. The high absorptive losses at low wavelengths (about 625 nm ) cause an interesting behavior, since the highest Deltaepsilom do not produce the greatest eta. The highest eta is produced for a hologram thickness in the range of 900-1000 microm and working wavelength of 700-750 nm.

Optical Image Contrast Reversal Using Bacteriorhodopsin Films

The implementation of image contrast reversal by using a photochromicmaterial of Bacteriorhodopsin (BR) films is demonstrated with twomethods based on the optical properties of BR. One is based on theabsorption difference between the B and M states. Images recorded bygreen light can be contrast reversed readout by violet light. The otheris based on the photoinduced anisotropy of BR when it is excited bylinear polarization light. By placing the BR film between two crossedpolarizers (i.e. a polarizer and an analyser), the difference ofpolarization states of the recorded area and the unrecorded area can bedetected, and thus different contrast images can be obtained byrotating the polarization axis of the analyser.

Time-dependent all-optical logic-gates with bacteriorhodopsin film

In this paper, we proposed time-dependent AND, NOT and A ¯ B operation based on the relation between input and output intensities of the first-order diffraction beams in degenerate multi-wave coupling. When two coherent green beams are coupled in bacteriorhodopsin (bR) film with a small angle, the intensities of the diffraction beams decrease along with writing time. Based on the phenomenon that the diffraction beams decay along with writing time and the relation between the intensities of input and output beams, we demonstrated the time-dependent optical AND, NOT and A ¯ B operations.

All-optical logic-gates based on bacteriorhodopsin film

Based on self-diffraction in bacteriorhodopsin (bR) film, we propose all-optical NOT, XOR, half adder and XNOR logic operations. Using the relation between diffraction light and the polarization states of recording beams, we demonstrate NOT and XNOR logic operations. Studying the relation of polarization states among the diffracting, recording and reading beams, we implement XOR logic and half adder operations with three inputs. The methods are simple and practicable.

Real-time intensity-dependent all-optical switch of reverse image converter from wavelength to wavelength based on bacteriorhodopsin film

When suitable green writing laser beams are incident on bacteriorhodopsin film, the diffraction beams occur and their intensity changes as writing time. We theoretically analyzed this phenomenon and, based on this property, designed an all-optical image reverse converter switch, which has the ability to transfer an optical image from a laser beam (433nm) to another green laser beam (533nm) within the effective transfer time. Beyond the effective time, the image automatically stops transferring from one wavelength to another. The effective time is dependent on the intensities of writing beams.

Optical novelty filter using bacteriorhodopsin film

A new kind of optical novelty filtering by an incoherent light system is presented that is based on a special property of dynamic complementary suppression modulated transmission in bacteriorhodopsin film. By simplifying the energy system, we establish a theoretical model, and our experimental results are compared with those reached by numerical simulation of the novelty filter.

Experimental study on polarization holographic high density optical data storage with bacteriorhodopsin film

Genetic mutant bacteriorhodopsin BR_D96N film was experimentally studied on its holographic storage properties with different polarization recording waves. The influences of the different polarization states of the recording and readout wav es on the retrieval diffractive image's intensity and signal_to_noise_ratio were compared with each other. The experimental results showed that compared with ot her polarization holographic recording, orthogonal circular polarization recordi ng can realize the separation of the polarization state of the diffractive wave from the scattering noise, and thus has high signal_to_noise_ratio as well as hi gh diffraction efficiency. Using He_Ne laser (633nm, 3mW) as recording and reado ut beam, spatial light modulator as data input element and CCD as data capture e lement, orthogonal circular polarization holographic optical data storage was ma de on 60μm×42μm area of the BR_D96N film by Fourier transform holographic met hod. The area density of 2×108bit/cm2 was obtained, and t he encoded data was retrieved without errors.

Nonlinear optical Fourier filtering technique for medical image processing

Real-time nonlinear optical Fourier filtering for medical image processing is demonstrated, exploiting light modulating characteristics of thin films of the biophotonic material bacteriorhodopsin (bR). The nonlinear transmission of bR films for a 442 nm probe beam with a 568 nm control beam and vice versa is experimentally studied in detail. The spatial frequency information carried by the blue probe beam is selectively manipulated in the bR film by changing the position and intensity of the yellow control beam. The feasibility of the technique is first established with different shapes and sizes of phantom objects. The technique is applied to filter out low spatial frequencies corresponding to soft dense breast tissue and displaying only high spatial frequencies corresponding to microcalcifications in clinical screen film mammograms. With the aid of an electrically addressed spatial light modulator (SLM), we successfully adapt the technique for processing digital phantoms and digital mammograms. Unlike conventional optical spatial filtering techniques that use masks, the technique proposed can easily accommodate the changes in size and shape of details in a mammogram.

14-Fluoro-Bacteriorhodopsin Gelatin Films for Dynamic Holography Recording¶

The first dynamic holography recording using 14-fluoro-(14-F) bacteriorhodopsin (BR) gelatin films has been achieved. 14-F BR is an artificial BR pigment made by reconstitution of bacterioopsin (native BR without chromophore) with synthetic 14-F retinal. Low-intensity red light from a cw He-Ne laser was used for dynamic holography recording on the 14-F wild type (WT) BR and 14-F D96N mutant BR in gelatin films. There is not true comparing the diffraction efficiency for 14-F D96N BR and 14-F WT gelatin film, unlike the increased diffraction efficiency for D96N BR gelatin film with native chromophore relative to the WT BR gelatin film with native chromophore. Pre-illumination with blue light of the 14-F BR gelatin films significantly increases the diffraction efficiency of both the 14-F WT and the 14-F D96N BR pigments. The sequential application of blue and red laser beams indicates that 14-F BR gelatin films can be useful for optical memory.

Improvement of the diffraction efficiency and kinetics of holographic gratings in photochromic media by auxiliary light

Holographic gratings recorded in photochromic media often do not obtain the maximally achievable diffraction efficiency because of diminishing the fringe contrast caused, e.g., by a photochemically active readout beam or unequal intensities of object and reference waves. For nonreversible materials this problem causes a decrease in diffraction efficiency that is proportional to the signal-to-noise ratio (SNR). However, in nonlinear materials such as photochromic media, for which saturation effects need to be considered, an out-of-proportion decrease in the SNR results. It is shown that an overshooting peak during hologram growth, which then decays to a lower permanent level of diffraction, is an indicator for such a situation. Even a weak readout beam may cause such effects, which significantly affect the hologram kinetics. The observed overshooting diffraction efficiency may even be misinterpreted to be dependent on material properties. Experimental and theoretical proof that with low levels of auxiliary light this type of problem can be eliminated completely is presented. Throughout this research bacteriorhodopsin films were used, but the results are valid for photochromic media in general.

Medical image processing using transient Fourier holography in bacteriorhodopsin films

Real time image processing is demonstrated by recording and reconstructing the transient photoisomerizative grating formed in the bR film using Fourier holography. Desired spatial frequencies including both high and low band in the object beam are reconstructed by controlling the reference beam intensity. The results are in agreement with a theoretical model based on photoisomerization grating. We exploit this technique to process mammograms in real-time for identification of microcalcifications buried in the soft tissue for early detection of breast cancer. A feature of the technique is the ability to transient display of selected spatial frequencies in the reconstructing process which enables the radiologists to study the features of interest.

Dynamic Behaviour of Self-Diffraction in BacteriorhodopsinFilm

We investigate the dependences of the diffraction efficiency of thefirst order self-diffracted beam in bacteriorhodopsin (bR) films on theillumination time, the intensity and wavelength of the incident light.When the blue light (λ = 488 nm) and low intensity red light(λ = 632.8 nm) are incident on the bR filmrespectively, the diffraction efficiencies increase from zero to astable value with the illumination time. When the green light (λ = 533 nm) and high-intensity red light illuminate the bR filmrespectively, the diffraction efficiencies increase from zero to themaximum and then decrease to a stable value with the illumination time.Rise and decay times are dependent on the intensity and wavelength ofthe incident light. The maximal diffraction efficiency of the redlight is twice as high as that of the green light. The highestdiffraction efficiency of 5.4% is obtained at 633 nm. Thediffraction efficiency change with the time for the green light islarger than that for the blue and red light.

Broadband optical limiter based on nonlinear photoinduced anisotropy in bacteriorhodopsin film

Nonlinear photoinduced anisotropy in a bacteriorhodopsin film was theoretically and experimentally investigated and a broadband active optical limiter was demonstrated in the visible spectral range. A diode-pumped second harmonic yttrium aluminum garnet laser was used as a pumping beam and three different wavelengths at λ=442, 532, and 655nm from different lasers were used as probing beams. The pump and probe beams overlap at the sample. When the pumping beam is absent, the probing beam cannot transmit the crossed polarizers. With the presence of the pumping beam, a portion of the probing light is detected owing to the photoinduced anisotropy. Due to the optical nonlinearity, the transmitted probing beam intensity is clamped at a certain value, which depends on the wavelength, when the pumping beam intensity exceeds 5mW∕mm2. Good agreement between theory and experiment is found.

All-optical display using photoinduced anisotropy in a bacteriorhodopsin film.

Photoinduced anisotropy in a bacteriorhodopsin film using the pump-probe method was investigated. A diode-pumped second-harmonic YAG laser was used as the pump beam, and three wavelengths, at lambda = 442, 532, 655 nm, from different lasers were used as probe beams. Without the pump beam, the probe light cannot transmit the analyzer to the detector. However, because of photoinduced anisotropy, a portion of the probe light is detected when the pump beam is present. Based on this property, we demonstrate a full-color all-optical display.

Phase modulation by polarization recording in bacteriorhodopsin: application to phase-shifting interferometry.

A novel phase-control method with application to phase-shifting interferometry is presented. The linear polarization state of an external (green) light beam is recorded on a bacteriorhodopsin film, and this polarization state is read by a circular polarized (red) laser beam. By reading the bacteriorhodopsin film, the original (red) wave reverses its circularity and becomes phase shifted by an amount that is dependent on the polarization of the external (green) beam. This method of phase control can be applied in a two-beam interferometer in which the test and reference waves are orthogonally polarized, which allows one to obtain phase modulation without moving parts inside the interferometer.

Secure holographic memory by double-random polarization encryption.

A novel optical encryption based on polarization is proposed and applied to a holographic memory system. Original binary data are described as two orthogonal linear polarization states. These input polarization states can be modulated by use of two polarization-modulation masks located at the input and the Fourier planes. Each modulation mask can convert an input polarization state into a random polarization state. Once encrypted, the polarization state is recorded as a hologram. For the decryption, the hologram can generate a vector phase-conjugate beam. When the same polarization-modulation masks are used, the vector phase-conjugate readout can cancel the polarization modulation at each mask, and the original polarization state can be recovered. The encryption of the proposed method is evaluated numerically. We also present experimental results by demonstrating holographic recording in a bacteriorhodopsin film.

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.

Photonic switching based on the photoinduced birefringence in bacteriorhodopsin films

Photoinduced birefringence in bacteriorhodopsin films was investigated using pump–probe method and its application for photonic switching explored. A diode-pumped second-harmonic YAG laser was used as a pumping beam and a diode laser at λ=660 nm was used as a probing beam. The pump and probe beams overlap at the sample. Without the pumping beam, the probing light cannot transmit the analyzer to the detector. However, due to the photoinduced anisotropy, a portion of the probing light is detected when the pumping beam is present. Since λ=660 nm is far from the absorption peak (∼570 nm) of the ground state, the photoinduced birefringence predominates. Using the intensity-dependent photoinduced birefringence in a bacteriorhodopsin film, we have demonstrated a photonic switch with ∼1000:1 contrast ratio, ∼0.6 s rise time and ∼1.5 s decay time.

Bacteriorhodopsin as a high-resolution, high-capacity buffer for digital holographic measurements

Recent trends in optical metrology suggest that, in order for holographic measurement to become a widespread tool, it must be based on methods that do not require physical development of the hologram. While digital holography has been successfully demonstrated in recent years, unfortunately the limited information capacity of present electronic sensors, such as CCD arrays, is still many orders of magnitude away from directly competing with the high-resolution silver halide plates used in traditional holography. As a result, present digital holographic methods with current electronic sensors cannot record object sizes larger than several hundred microns at high resolution. In this paper, the authors report on the use of bacteriorhodopsin (BR) for digital holography to overcome these limitations. In particular, BR is a real-time recording medium with an information capacity (5000 line-pairs/mm) that even exceeds high resolution photographic film. As such, a centimetre-square area of BR film has the same information capacity of several hundred state-of-the-art CCD cameras. For digital holography, BR temporarily holds the hologram record so that its information content can be digitized for numeric reconstruction. In addition, this paper examines the use of BR for optical reconstruction without chemical development. When correctly managed, it is found that BR is highly effective, in terms of both quality and process time, for three-dimensional holographic measurements. Consequently, several key holographic applications, based on BR, are proposed in this paper.

Digital optical operation in multilateral systemby bacteriorhodopsin film

Bacteriorhodopsin film has a special property of complementary suppression modulated transmission of yellow and blue beams. Resolving the transmission rate equ ations of the yellow and blue beams, the analytical formulae are obtained and gr aphic results are shown. We put forward a multilateralsystem computational mod el of digital optical matrix addition and subtraction operations without carry a nd abdication respectively. The novel model and frame of basic optical computati on are constructed, and the optimized project of digital optical matrix addition and subtraction operations are designed.