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General limit of the storage capacity of the shift multiplexed holographic memory, and that with the Fourier holographic arrangement is summarized. Then the material limit and system limit of the collinear holographic memory are discussed.

We improved the photorefractive polymer with mixing two kinds of nonlinear chromophores. Diffraction efficiency of 16 % with 0.1 mm thick sample, and shelf lifetime of more than 2 months were obtained.

Two-wave-mixing gain coefficient and time constant are measured at a wavelength of 457.8 nm. To avoid the effect of photochromism, we employed a polarization modulated interferometer. The origin of photochromism is assigned to Fe-ion-related transition.

We propose a method to read the volume hologram at a wavelength different from the recording one. Whole the image can be reconstructed using a spectrally broad but spatially coherent light source.

We report on the null reconstruction of polarization volume hologram recorded by orthogonal circularly polarized waves with a large cross angle. Based on the recently developed tensor theory for polarization holography, the disappearance of the reconstruction was analytically verified, where a nice agreement was found between the experimental and theoretical results. When the polarization and intensity hologram attain a balance, not only the null reconstruction but also the faithful reconstruction can be realized by the illumination of the orthogonal reference wave and original reference wave. As a consequence of the hologram recorded without paraxial approximation, the null reconstruction may lead to important applications, such as a potential enhancement in optical storage capacity for volume holograms.

The Pb(Zn1/3Nb2/3)-PbTiO3 crystals are grown by the flux solution methods with 3 kinds of dopants, Fe, Mn, and Rh. Photorefractive properties are investigated. We also measure the extinction spectra including the scattering, electrooptic coefficients, photoconductivity, and photovoltaic effect. The two-wave-mixing gain of more than 20 cm-1 is obtained

Holographic Versatile Disc (HVD TM ) using Collinear TM Technologies is proposed by OPTWARE Corporation, in which the information and reference beams are displayed co-axially by the same SLM. With this unique configuration the optical pickup can be designed as small as the DVD's, and can be placed on one side of the recording disc. In HVD TM structure, the pre-formatted meta-data reflective layer is used for the focus/tracking servo and reading address information, and the dichroic mirror layer is used for detecting holographic recording information without interfering with the preformatted information. A 2-dimensional digital page data format is used and the shift-multiplexing method is employed to increased recording density of HVD TM . Experimental and theoretical studies suggest that the holographic material is very effective to increased recording density of the system. As the servo technology is being introduced to control the objective lens to be maintained precisely to the disc in the recording and the reconstructing process, a vibration isolator is no longer necessary. HVD TM will be compatible with existing disc storage systems, like CD and DVD, and enable us to expand its applications into other optical information storage systems.

Numerical simulations of the signal decay with media shift were performed. Principle of the shift selectivity of the data pages are explained with our simple numerical model. D ecay of the diffracted signal is calculated with the shift of the media. The dependencies of the shift selectivity on the reference pixel patterns, radius and width of the of the reference pixel area, and the media thickness. Shift selectivity of the page does not depend on the media thickness or reference pixel patterns. It is mainly determined by the radius and the width of the reference pixel area. Keywords: Holographic data storage, collinear system, storage density 1. INTRODUCTION Advantages of the collinear holographic memory have been reported in several papers and reports [1-3]. We proposed a simple model to simulate the image formation of the collinear holographic system, and proposed the concept of the pixel spread function (PxSF) [4,5]. It well describes the image formation in the collinear holographic system. We revealed that the Bragg degeneracy [6] affects the sharpness of the PxSF greatly, and the wheel like reference pattern shows the better PxSF than the thick ring reference pattern. Also, thicker recording media give sharper PxSF. It is quite different property compared with normal angle multiplexed holographic memory. Here we will show that the shift selectivity of the collinear holographic system is determined by the reference pixel pattern. 2. Numerical model We used the same model as ref. 4, shown in Fig. 1. The model optical system for our simulation is shown in Fig.1 [4]. The pixel pitch of the spatial light modulator (SLM) was 13.7 µ m, the focal length of the lens, f, was 4 mm, and the wavelength of the light was 408 nm in our calculations. The Fresnel number for the single pixel at the lens, which is calculated with the parameters above, was about 0.12, thus, the diffracted light from single pixel of SLM is in Fraunhofer regime. The optical field has approximately sphere wave front and the amplitude distribution is proportional to two dimensional sinc function. After the lens, the light wave from each pixel propagates as a plane wave. Near the secondary focal point of the lens in the medium, all waves from the open pixels are crossing and all the combinations of two plane waves make interference fringes. The wave vector k of each plane wave is determined by the position of the corresponding pixel of SLM. Each k vector of the plane wave and the pixel of the SLM corresponds one-to-one with the pixel of the SLM.

The S-phase DNA damage checkpoint is activated by DNA damage to delay DNA synthesis allowing time to resolve the replication block. We previously discovered the p53-dependent S-phase DNA damage checkpoint in mouse zygotes fertilized with irradiated sperm. Here, we report that the same p53 dependency holds in mouse embryonic fibroblasts (MEFs) at low doses of irradiation. DNA synthesis in p53 wild-type (WT) MEFs was suppressed in a biphasic manner in which a sharp decrease below 2.5 Gy was followed by a more moderate decrease up to 10 Gy. In contrast, p53-/- MEFs exhibited radioresistant DNA synthesis below 2.5 Gy whereas the cells retained the moderate suppression above 5 Gy. DNA fiber analysis revealed that 1 Gy irradiation suppressed replication fork progression in p53 WT MEFs, but not in p53-/- MEFs. Proliferating cell nuclear antigen (PCNA), clamp loader of DNA polymerase, was phosphorylated in WT MEFs after 1 Gy irradiation and redistributed to form foci in the nuclei. In contrast, PCNA was not phosphorylated and dissociated from chromatin in 1 Gy-irradiated p53-/- MEFs. These results demonstrate that the novel low-dose-specific p53-dependent S-phase DNA damage checkpoint is likely to regulate the replication fork movement through phosphorylation of PCNA.

In this paper, we present the GV-matched second- and third-harmonic (TH) generations (THG) of femtosecond pulses in a 2D NPC. In our device, two gratings with different periods (11.6/spl mu/m and 9.36/spl mu/m) are superimposed with an angle of 12/spl deg/, to satisfy the noncollinear QPM conditions for SHG and THG, respectively. In this experiment, TH efficiency was 2% under the condition where the maximum SH efficiency of 25% was obtained.

Most of semi-insulating compound semiconductors show photorefractive effect. Its photorefractive response is quite fast compared with paraelectric and ferroelectric crystals, or organic materials. Sometimes the effect is enhanced by the band edge effect such as the electroabsorption. However, photorefractive effect has not been reported in nitride semiconductors, which are intensely studied as promising nonlinear optical materials for the blue and ultra-violet wavelength region. In this paper, we report the observation of the photorefractive two-beam coupling in semi-insulating GaN thin crystal.

We study adiabatic soliton compression of femtosecond pulses in second harmonic generation by using chirped quasi-phase-matching gratings in the absence of group velocity mismatching. Two GV-matching schemes on collinear and non-collinear QPM are numerically investigated.

Photorefractive properties of Fe, Mn, and Rh doped 0.91Pb(Zn 1/3 Nb 2/3 )O 3 -0.09PbTiO 3 (0.91PZN-0.09PT) are investigated. Relaxor ferroelectric crystals are expected to show large photorefractive effect due to its large piezoelectric effect near morphotropic phase boundary (MPB). Crystals are grown by flux solution method, then cut, polished, and poled along [110] direction. Absorption spectrum, photorefractive two-beam coupling gain, and response speed were measured as functions of the grating period, and light intensity, at several wavelengths for each doped and undoped samples. Photoconductivity and photochromism in Fe doped crystal were estimated. Fe doping enhanced the photorefractive effect and net two-beam coupling gain of 19 cm -1 was obtained. Rh doping increased the gain at 633 nm compared to the undoped sample. From the intensity dependence of the two-beam coupling gain, two-center model is suitable for explaining the photorefractive properties of Fe doped samples. For all samples, doping of the ions slowed down the response speed because of the decrease of the photoconductivity.

We developed a stable PVK-based photorefractive polymer composite. Response time was 33 ms and diffraction efficiency was 49% at an electric field of 100 2 kV/mm and a total writing intensity of 942 mW/cm 2

The photorefractive effect was observed in He-ion-implanted semi-insulating GaN film in UV spectral region. The photorefractive grating is induced by the electroabsorption effect near the band-edge. Two beam coupling experiments were performed at a wavelength of 363.8 nm. The experimental results indicate that absorption grating mainly contributes to the beam coupling effect.

We have generated femtosecond pulses of 700-nm bandwidths in a 3–4 µm spectral range by an optical parametric amplifier based on periodically-poled LiNbO3. Numerical study indicates the possibility for generating ∼25-fs pulses by pre-chirp compensation.

We present an optically driven microsphere sorting system based on the optical trapping technique. The liquid crystal panel is used as a spatial light modulator to create double well shaped optical potential where particles are trapped metastably. The constructed optical potential barrier is observed to be different, depending on particle's size. The sorting experiment showed that there exists an optimum condition in order to accurately sort out particles with different sizes.

We report the nonvolatile holographic recording in the Ru and Fe doped LiNbO3 crystal. The nonvolatile hologram can be recorded at a wavelength of 632.8 nm when the gating beam (blue light) is simultaneously incident on the crystal. The recorded hologram can be successfully fixed and transformed into a nonvolatile hologram keeping the hologram strength almost unchanged. The recording sensitivity and dynamic range increase with the increase of the Fe concentration. The sensitivity of 0.12 cm/J and the dynamic range of 0.53 are obtained at the 0.5-mm-thick sample.

We modified structure of nonlinear optical chromophore by attaching alkyl groups to improve the shelf lifetime while keeping a low glass transition temperature. We obtained a sample with modified NLO, 4-(2-ethylhexyloxy)-3-propyl-1-(4'-nitoro phenylazo)benzene (m3p2,6) which has a longer shelf lifetime of more than five months. In PVK:m3p2,6:BisCzPro:TNF (50:46:3:1 wt%) composite, the photorefractive response rate was 33 ms and diffraction efficiency was 49%, at an electric field of 100 V/µm and a total writing intensity of 942 mW/cm2. These results of high-performance should be due to the following reasons: first, the chromophore m3p2,6 acts as a plasticizer and has a larger free volume thereby enhancing the orientation of chromophore, and second, the solubility of the chromophore in polymer matrix increases, inhibiting crystallization.

A numerical simulation method to evaluate the collinear holographic memory is proposed. A pixel spread function is defined and the resolving power of the page data image increases with the increase of the media thickness.

Large photorefractive effect is observed in Fe-doped 0.91PZN-0.09PT relaxor ferroelectric crystal grown by the flux method. Moreover, the photochromism is induced by the illumination of blue or green laser light.

We perform two kinds of computer simulations on polydisperse hard‐sphere systems; a molecular‐dynamics simulation on atomic systems and a Brownian‐dynamics simulation on colloidal suspensions. By the analyses of the mean square displacement and the radial distribution function, the simulation results suggest that the long‐time behavior of colloidal suspensions is exactly the same as that of atomic systems. It is also shown that there exist three phase regions, a liquid phase region, a metastable phase region, and a crystal phase region, where the freezing and melting points in polydisperse case are shifted to the values higher than in monodisperse case.

We report the nonvolatile holographic recording in a Ru and Fe doped LiNbO/sub 3/ crystal. The recorded hologram can be fixed as a nonvolatile hologram, without a considerable decrease of the hologram strength.

The polymer composites under investigation consist of the hole-transporting polymer poly(N-vinylcarbazole) (PVK), the charge generating molecule 2,4,7-trinitro-9-fluorenone (TNF), the plasticizer 1,3-bis(N-carbazolyl) propane (BisCzPro), and nonlinear optical (NLO) chromophore. We carried out a series of measurements in order to characterize the photorefractive polymers: transmission spectrum; glass transition temperature T/sub g/; speed of reorientation under the application of an electric field of 54 V//spl mu/m and birefringence induced by the applied field using a polarimetric technique; photorefractive diffraction efficiency and response time as a function of incident intensity using a four-wave mixing geometry; and photorefractive gain coefficient and the photorefractive phase shift using a two-wave mixing geometry. We have successfully accelerated the response of NLO chromophores by modifying the structure of DNMAA without any degradation of diffraction efficiency. The photorefractive response of our samples is limited by the formation of space charge distribution.

Summary form only given. In this paper, a secure display system by use of encrypted digital holograms is presented. The original image is encrypted by random phase masks and then recorded as a digital hologram. The encrypted digital hologram is decrypted in a joint transform correlator architecture by using a key digital hologram. The encrypted digital holograms can be transmitted to remote users by communication channels, therefore the proposed system can be used for secure two-dimensional or three-dimensional display systems.

Summary form only given. We observed the photorefractive effect in relaxor ferroelectric crystal PZN-PT by two-wave mixing. We have found that crystals have a large photorefractive gain coefficient. Two-beam coupling experiments were performed at /spl lambda/ = 633 nm to examine the photorefractive properties. All the experiments were conducted in extraordinary polarization of light to utilize the electrooptic coefficient r/sub 33./ The experimental results of gain coefficients are shown as a function of grating period. A maximum gain coefficient is recorded up to 7 cm/sup -1/ at a grating period of 1.8 /spl mu/m. The effective trap density and effective electrooptic coefficient are estimated to be 1. 1 /spl times/ 10/sup 16/ cm/sup -3/ and 103 pm/V, respectively, by fitting the theory based on the standard band transport model to the experimental data.

Summary form only given. Photorefractive multiple quantum wells (MQWs) have become important for the realization of fast and two-dimensional optical image processing devices. Wang et al. have reported the photorefractive effect in InGaAs-GaAs MQWs around 0.9 /spl mu/m. But the details of two-wave mixing (TWM) have not been mentioned. Here we report the photorefractive effect including the TWM properties in InGaAs-GaAs MQWs around a wavelength of 0.93 /spl mu/m.

An all-optical image brightness amplifier is a key device in parallel optical data processing systems. It works like an Er-doped fiber amplifier in optical fiber communication systems. The laser image amplifier can recover the energy loss of the spatially two-dimensional and temporally one-dimensional optical signal without losing the phase information of the light. Recently, solid dye laser materials have improved steadily, and the dye doped polymer amplifier is now commercially available. Also, diode-pumped Nd:YAG laser systems also become very popular. Thus, the reality of a compact all solid state laser image amplifier system is growing. In the paper, we show the basic performance of the polymer dye laser amplifier system for an image amplification system.

We report on nonvolatile holographic recording in Ru doped LiNbO3 crystal, to our knowledge, for the first time. Irradiation of the blue light induces the absorption change in the spectral range up to 650 nm. The nonvolatile hologram can be recorded at the recording wavelength of 632.8 nm when the blue light is simultaneously incident on the crystal. The diffraction efficiency of the nonvolatile hologram is about 1 % at the extraordinary polarization.

We synthesized new chromophores that have modified structures of DMNPAA. Among them, a 4-butoxy-3-propyl-1-(4?-nitrophenyazo)benzene composite improves the response speed quite well. We obtained the reorientation time constant of 19ms (@54V/?m), which is 2,300 times faster than of DMNPAA at room temperature. The speedup of orientational response is caused by the improvement of dispersivity in the polymer composite and the decrease of glass transition temperature. The temperature dependence of photorefractive properties of poly(N-vinlycarbasole) (PVK)-based composite is studied in the temperature range of 5-60°C. The experimental results show that the reorientation speed increases with the increase of temperature. The diffraction efficiency first increases with the increase of temperature, and then decreases as temperature is further increased.

We report a femtosecond pulse compression using cascaded second-order nonlinearities. Pulse compression from 120 fs down to 67 fs is obtained by using lithium iodate crystal as a nonlinear medium.

We numerically evaluate the security capability of double random polarization encryption. Numerical results show that double polarization encryption has the same potential as double random phase encryption.

Pulse compression is a well-established technique for shortening pulses generated by oscillators or amplifiers. In practice, pulses can be compressed using two stages, one for spectrum broadening and the other for dispersion compensation. A commonly used technique consists of self-phase modulation in an optical fiber and the group-velocity dispersion provided by gratings or prisms. Such compressors, however, have several drawbacks, such as coupling loss, limitation on pulse energies, etc. Recent research has shown that cascaded second-order nonlinearities can generate nonlinear phase shift similar to the optical Kerr effect. We report spectrum broadening in femtosecond pulses by cascaded nonlinearities, and the numerical study on it. We particularly investigated the influence of the temporal walk-off between fundamental and second harmonic pulses. A mode-locked Ti:sapphire oscillator and a regenerative amplifier generate a 120 fs, 800 nm pulse at 1 kHz repetition rate. The BBO crystal is 7x7x7 mm/sup 3/ size and cut for type I phase matching angle.

The MBE fabrication of an InGaAs-GaAs MQW photorefractive p-i-n diode and its photorefractive properties are reported. We also discuss the difference in photorefractive performance between p-i-n diode and previous dielectric buffered devices.

Some characteristics of photorefractive semiconductor multiple quantum well devices are discussed from the point of view of a material for the vibration measurement system using two-wave mixing. Device structure and device fabrication is explained, and some results of the measurements on the characteristics of the device are presented and discussed. Finally, the system of vibration measurements is described and some results are discussed. The smallest detectable amplitude of the vibration is 0.4 nm and the signal is linear up to 25 nm. Cut off frequency is 34 kHz at the incident intensity of 90mW/cm2.

Untargeted mutation and delayed mutation are features of radiation-induced genomic instability and have been studied extensively in tissue culture cells. The mouse pink-eyed unstable (p(un)) mutation is due to an intragenic duplication of the pink-eyed dilution locus and frequently reverts back to the wild type in germ cells as well as in somatic cells. The reversion event can be detected in the retinal pigment epithelium as a cluster of pigmented cells (eye spot). We have investigated the reversion p(um) in F1 mice born to irradiated males. Spermatogonia-stage irradiation did not affect the frequency of the reversion in F1 mice. However, 6 Gy irradiation at the spermatozoa stage resulted in an approximately twofold increase in the number of eye spots in the retinal pigment epithelium of F1 mice. Somatic reversion occurred for the paternally derived p(un) alleles. In addition, the reversion also occurred for the maternally derived, unirradiated p(un) alleles at a frequency equal to that for the paternally derived allele. Detailed analyses of the number of pigmented cells per eye spot indicated that the frequency of reversion was persistently elevated during the proliferation cycle of the cells in the retinal pigment epithelium when the male parents were irradiated at the spermatozoa stage. The present study demonstrates the presence of a long-lasting memory of DNA damage and the persistent up-regulation of recombinogenic activity in the retinal pigment epithelium of the developing fetus.

One difficulty in analyzing the damage response is that the effect of damage itself and that of cellular response are hard to distinguish in irradiated cells. In mouse zygotes, damage can be introduced by irradiated sperm, while damage response can be studied in the unirradiated maternal pronucleus. We have analyzed the p53-dependent damage responses in irradiated-sperm mouse zygotes and found that a p53-responsive reporter was efficiently activated in the female pronucleus. [(3)H]thymidine labeling experiments indicated that irradiated-sperm zygotes were devoid of G(1)/S arrest, but pronuclear DNA synthesis was suppressed equally in male and female pronuclei. p53(-/-) zygotes lacked this suppression, which was corrected by microinjection of glutathione S-transferase-p53 fusion protein. In contrast, p21(-/-) zygotes exhibited the same level of suppression upon fertilization by irradiated sperm. About a half of the 6-Gy-irradiated-sperm zygotes managed to synthesize a full DNA content by prolonging S phase, while the other half failed to do so. Regardless of the DNA content, all the zygotes cleaved to become two-cell-stage embryos. These results revealed the presence of p53-dependent pronuclear cross talk and a novel function of p53 in the S-phase DNA damage checkpoint of mouse zygotes.

We present femtosecond measurements of nonlinear refraction in periodically poled lithium tantalate by using spectrally resolved two-beam coupling. The sign and magnitude of nonlinear phase shifts induced by cascade quadratic nonlinearity and intrinsic Kerr nonlinearity are measured.

We present the temporal soliton compression of femtosecond pulses in quadratic media, where cascade quadratic nonlinearity and normal dispersion contribute for compression. Compression factor of 3 is achieved by using-30 mm long beta-barium borate.

Cyclin D1 expression is precisely controlled during cell-cycle progression. However, repeated exposure to low-dose fractionated radiation (FR) abrogates cell cycle-dependent cyclin D1 degradation by constitutive activation of AKT survival signaling in normal human fibroblasts. The resulting abnormal nuclear cyclin D1 accumulation induces defects in DNA replication and resulting DNA double-strand breaks, and is associated with induction of genomic instability in low-dose irradiated cells. Here, we investigated the role of DNA damage signaling against such perturbed cell-cycle control of cyclin D1 expression. Nuclear cyclin D1 accumulation was induced within 7 days after low-dose FR (0.01 Gy or 0.05 Gy per fraction) in ATM-deficient cells (AT5BIVA), but appeared later in AT5BIVA cells harboring human ATM cDNA. Thus, ATM prevents abnormal nuclear cyclin D1 accumulation at early time points after low-dose FR. We further demonstrated that ATM-mediated downregulation of protein phosphatase 2A activity caused activation of the AKT/cyclin D1 pathway after long-term FR. Perturbation of cyclin D1 expression induced Rad51 foci that indicate homologous recombination repair (HRR) in control cells, while ATM- and NBS1-deficient cells (GM7166) failed to induce Rad51 foci after long-term low-dose FR. After 21 days of FR, NBS1- and ATM-deficient cells showed a decrease in nuclear cyclin D1-positive cells, and an increase in apoptotic cells. Similarly, inhibition of ATM with KU55933 abrogated nuclear cyclin D1 accumulation by induction of apoptosis in ATM-complemented cells exposed to low-dose FR. In conclusion, we here demonstrate that ATM is involved in controlling cyclin D1 levels after low-dose FR. DNA damage signaling mitigates the harmful effects of low-dose long-term FR by suppression of cell death induced by perturbation of cyclin D1 expression.

A phase-controlled spin wave was non-thermally generated in bismuth-doped rare-earth iron garnet by linearly polarized light pulses. We controlled the initial phase of the spin wave continuously within a range of 180 deg. by changing the polarization azimuth of the excitation light. The azimuth dependences of the initial phase and amplitude of the spin wave were attributed to a combination of the inverse Cotton-Mouton effect and photoinduced magnetic anisotropy. Temporally and spatially resolved spin wave propagation was observed with a CCD camera, and the waveform was in good agreement with calculations. A nonlinear effect of the spin excitation was observed for excitation fluences higher than 100 mJ/cm^2.

The effect of caffeine was studied on the radioresponses of undifferentiated mouse embryonal carcinoma cells (EC cells) with or without the functional p53. The radioresponses studied included radiosensitivity, the activation of p53, apoptosis with characteristic DNA ladder formation and cell cycle progression. An undifferentiated mouse EC cell line, ECA2, and a newly established p53-deficient EC cell line, p53 delta, were used in the present study. The status of the p53 gene did not significantly affect the colony survivals of undifferentiated EC cells to X-rays and UV. Although a post-irradiation treatment with caffeine sensitized both lines to X-rays marginally, the sensitization was prominent for UV regardless of the p53 status of the cells. The activation of a p53 responsible lacZ reporter construct was observed in stably transfected ECA2 cells after X-ray and UV irradiations. Caffeine suppressed the X-ray induced activation of the lacZ reporter, while it drastically enhanced the activation after UV irradiation. X-rays and UV readily triggered the apoptosis of ECA2 cells with the characteristic DNA ladder. Although UV-induced DNA ladder formation was enhanced by caffeine, that induced by X-rays was unaffected. Therefore, the effects of caffeine on the p53-dependent radioresponses were found to be agent specific: suppression for the X-ray induced and augmentation for the UV induced. In contrast to p53-proficient ECA2 cells, smear-like DNA degradation was observed for irradiated p53 delta cells, suggesting the presence of a mode of cell death without DNA ladder formation. UV induction of the smear-like DNA degradation was enhanced in the presence of caffeine. Regardless of the state of the p53 gene, G1/S arrest was not observed in X-ray and UV irradiated EC cells. X-ray induced G2/M arrest in both lines, which was abrogated by caffeine, while G2/M arrest after UV was unaffected by a caffeine treatment. These results indicate that the radioresponses of undifferentiated EC cells differ considerably from those of somatic cells, and that these radioresponses were modulated by a post-irradiation treatment with caffeine.

Several lines of evidences from us or other authors had shown that tumor cells revert their phenotypes and differentiate by the elimination of oncogenes amplified on the acentric double minutes (DMs). The selective incorporation of DMs into the cytoplasmic micronuclei was thought to be involved in this elimination, however, the mechanism by which the content of micronuclei was eliminated from the cells remains to be discovered. In this report, we show the finding and the characterization of the extruded micronuclei in the culture fluid of human COLO 320DM tumor line, and suggest that the extrusion of micronuclei mediates the selective elimination of DMs. The extracellular micronuclei enriched with DMs had an apparently normal cytoplasmic membrane, decondensed chromatin and nuclear lamin protein, and their DNA did not suffer any extensive degradation. These characteristics were closely related to their cytoplasmic counterpart and clearly differentiated from the apoptotic bodies. We also developed a method for purifying the extracellular micronuclei. In this paper, the implications of the micronuclear extrusion are discussed.

We have fabricated photorefractive InGaAs/GaAs multiple quantum wells operating at a wavelength of 1064 nm and have characterized its photorefractive properties in the Franz-Keldysh geometry. A maximum gain coefficient of 200 cm-1 and a maximum four-wave mixing diffraction efficiency of 0.07% are obtained at an applied field of 15 kV/cm. Adaptive vibration measurement in a two- wave mixing configuration has also been demonstrated. The noise equivalent surface displacement of our measurement system is estimated at about 1.5xl0-6 nm(W/Hz)1/2.

A novel security technique based on polarization encryption is proposed and is applied to a secure holographic memory system. Original binary data are described as two orthogonal linear polarization states. These input polarization states can be modulated by two polarization modulation masks located at the input and the Fourier planes. Each modulation mask can convert an input polarization state into an arbitrary elliptical polarization state. After the encryption of the polarization state, this encrypted polarization state is recorded as a hologram that can generate a vector phase conjugate beam. In the decryption process, the vector phase conjugate readout can cancel the polarization modulation at each mask and then the original polarization state can be recovered. The encryption and the decryption are demonstrated experimentally in a bacteriorhodopsin film.

Design of quantum-well structure and cladding layers is a key issue to improve the performance of photorefractive semiconductor multiple quantum well (MQW) p-i-n diodes operated in the longitudinal-field geometry. We investigated device structures for (i) improving spatial resolution and (ii) expanding spectral bandwidth. Reduction of potential difference between the MQW region and the cladding layer has significantly improved the spatial resolution in InGaAs/GaAs p-i-n diode. We also propose a new approach to expand the diffraction bandwidth by employing asymmetric coupled quantum well (ACQW) structures. Diffraction has been observed at a spectral range over 30 nm in AlGaAs/GaAs ACQW p-i-n diode. Photorefractive ACQW devices will be suitable for applications such as optical short-pulse processing.

We propose a novel technique to enhance a non-volatile photorefractive grating in a two-color holographic recording. Resultant diffraction efficiency is increased by an applied external electric field in the fixing process. The influence of the external electric field is investigated both experimentally and theoretically. In an iron and manganese co-doped lithium niobate crystal, resultant diffraction efficiency was enhanced from 0.4 % to 1.7% when a 10 kV/cm electric field was applied anti-parallel to the +c-axis.