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Ligand-protected gold clusters are widely used in biosensors and catalysis. Understanding the structural evolution of these kinds of nanoclusters is important for experimental synthesis. Herein, based on the particle swarm optimisation algorithm and density functional theory method, we use [Au1(SH)2]n, [Au2(SH)3]n, [Au3(SH)4]n (n = 1-3) as basic units to research the structural evolution relationships from building blocks to the final whole structures. Results show that there is a 'linering- core' structural evolution pattern in the growth process of the nanoclusters. The core structures of the ligand-protected gold clusters consist of Au3, Au4, Au6 and Au7 atoms. The electronics and optics analysis reflects that stability and optical properties gradually enhance with increase in size. These results can be used to understand the initial growth stage and design new ligand-protected nanoclusters. [ABSTRACT FROM AUTHOR]

CUL4B ubiquitin ligase belongs to the cullin-RING ubiquitin ligase family. Although sharing many sequence and structural similarities,CUL4Bplays distinct roles in spermatogenesis from its homologous protein CUL4A. We previously reported that genetic ablation of Cul4a in mice led to male infertility because of aberrant meiotic progression. In the present study, we generated Cul4b germ cell-specific conditional knock-out (Cul4bVasa), as well as Cul4b global knock-out (Cul4bSox2) mouse, to investigate its roles in spermatogenesis. Germ cell-specific deletion of Cul4b led to male infertility, despite normal testicular morphology and comparable numbers of spermatozoa. Notably, significantly impaired sperm mobility caused by reduced mitochondrial activity and glycolysis level were observed in the majority of the mutant spermatozoa, manifested by low, if any, sperm ATP production. Furthermore, Cul4bVasa spermatozoa exhibited defective arrangement of axonemal microtubules and flagella outer dense fibers. Our mass spectrometry analysis identified INSL6 as a novel CUL4B substrate in male germ cells, evidenced by its direct polyubiquination and degradation by CUL4B E3 ligase. Nevertheless, Cul4b global knock-out males lost their germ cells in an age-dependent manner, implying failure of maintaining the spermatogonial stem cell niche in somatic cells. Taken together, our results show that CUL4B is indispensable to spermatogenesis, and it functions cell autonomously in male germ cells to ensure spermatozoa motility, whereas it functions non-cell-autonomously in somatic cells to maintain spermatogonial stemness. Thus, CUL4B links two distinct spermatogenetic processes to a single E3 ligase, highlighting the significance of ubiquitin modification during spermatogenesis. [ABSTRACT FROM AUTHOR]

Nucleotide excision repair (NER) is the primary DNA repair pathway that removes helix-distorting DNA strand damage induced by ultraviolet light irradiation or chemical carcinogens to ensure genome integrity. While the core NER proteins that carry out damage recognition, excision, and repair reactions have been identified and extensively characterized, and the NER pathway has been reconstituted in vitro, the regulatory pathways that govern the threshold levels of NER have not been fully elucidated. This mini-review focuses on recently discovered transcriptional and post-translational mechanisms that specify the capacity of NER, and suggests the potential implications of modulating NER activity in cancer prevention and therapeutic intervention. J. Cell. Physiol. 224: 585–589, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

We obtain analytical solutions of the coupled wave equations that describe the Bragg diffraction of ultrashort pulsed finite beams by a thick planar grating, using two-dimensional coupled wave theory. The diffraction properties for the case of an ultrashort pulsed finite beam with Gaussian profiles in both the time and spatial domains are investigated. The spectral bandwidth of the diffracted beam, the Bragg selectivity bandwidth and the diffraction efficiency of the volume grating are influenced by the geometry parameter and the input bandwidth. Therefore extra attention should be paid to designing optical elements based on volume gratings for use with ultrashort pulsed waves in applications of pulse shaping and processing. [ABSTRACT FROM AUTHOR]

A cascaded Fresnel digital hologram (CFDH) is proposed, together with its mathematical derivation. Its application to watermarking has been demonstrated by a simulation procedure, in which the watermark image to be hidden is encoded into the phase of the host image. The watermark image can be deciphered by the CFDH setup, the reconstructed image shows good quality and the error is almost close to zero. Compared with previous technique, this is a lensless architecture which minimizes the hardware requirement, and it is used for the encryption of digital image. [ABSTRACT FROM AUTHOR]

A nonvolatile recording scheme is proposed using LiNbO 3 :Ce:Cu crystals and modulated UV light to record gratings simultaneously in two centres and using red light to bleach the grating in the shallow centre to realize persistent photorefractive holographic storage. Compared with the normal UV-sensitized nonvolatile holographic system, the amplitude of refractive-index changes is greatly increased and the recording sensitivity is significantly enhanced by recording with UV light in the LiNbO 3 :Ce:Cu crystals. Based on jointly solving the two-centre material equations and the coupled-wave equations, temporal evolutions of the photorefractive grating and the diffraction efficiency are effectively described and numerically analysed. Roles of doping levels and recording-beam intensity are discussed in detail. Theoretical results confirm and predict experimental results. [ABSTRACT FROM AUTHOR]

In this paper is described a novel technique for producing an electro-optical intensity synthesizer which can generate different periodic time domain waveforms through only sine or cosine wave applied-voltages. The synthesizer presented here consists of a series of stages between two polarizers, with each stage consisting of an electro-optic element and a compensator. Every electro-optical element has the same applied-voltage function but different azimuth angles and ratios between the longitudinal and transverse lengths. The main principle is the synthesis of an electro-optic effect and a polarization interference effect in the time domain. This technique is based on an expanded Fourier positive-direction searching algorithm, which can not only simplify the calculation process but also produces many choices of structural parameters for different waveforms generation. A three-stage synthesis of an electro-optical birefringent system for continuous square waveform is undertaken to prove the principle. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we describe a wide-angle laser beam scanner and the rigorous result of the wide-angle laser beam scanner was obtained with the help of the vector refraction theory. Using the rigorous results, the distortion of the beam shape was discussed. The distortion of the beam shape is varying with the different relative angles of the double prisms. According to the conservation of the energy, the distribution of the laser intensity is changed too. [Copyright &y& Elsevier]

Abstract: In this paper, we present a simple technique to determine the coupling efficiency between a laser diode and a lensed-tip based on the ABCD transformation matrix method. We have compared our analysis technique to that of previous work and have found that the presented method is reliable in predicting the coupling efficiency of lensed-tip and has the advantage of simplicity of coupling efficiency calculation even by a pocket calculator. The results can be useful for designing coupling optics. [Copyright &y& Elsevier]

The general formulation of double refraction or internal double reflection for any directions of incidence and arbitrary orientation of the optic axis in a uniaxial crystal is analysed in terms of Huygens' principle. Then double refraction and double reflection along the sequential interface are chosen appropriately, the range of angular separation between the ordinary ray and extraordinary ray can be much greater. It is useful crystal element design. Finally, as an example, an optimum design of the output end interface for a 2 x 2 electro-optic switch is given. [ABSTRACT FROM AUTHOR]

The polarizing properties of crossed-beam volume holographic gratings recorded by arbitrary polarization plane waves are considered, using the three-dimensional coupled wave theory. Simple analysis expressions for the amplitude profiles of the transmitted and diffracted waves are obtained. Detailed diffraction characteristics for the case of a finite plane wave of uniform amplitude distribution are presented. We discuss the influence of the polarized azimuths of the incident wave both at recording and at reconstruction on the amplitude profiles of the transmitted and diffracted waves. [ABSTRACT FROM AUTHOR]

A packagable free-space two-dimension optical crossbar network is described, and extended to three-dimension physical space. The interconnection between two neighbor switch stages is implemented only use a calcite slab and the bypass-exchange switch is also integrated in a LiNbO3 slice. So a basic building block only consists of a bypass-exchange switching array or matrix for processing and a calcite slab for optical interconnection. A packaged crossbar network can be constructed by cascading such building blocks. The signal-to-noise ratio and cascadability of the network are discussed. It is shown that the crossbar network is compact configuration, solid state, low energy loss, easy to cascade and assemble, and insensitive to disturbance. [ABSTRACT FROM AUTHOR]

The general formulation of double refraction or internal double reflection with different directions of propagation vector and wave vector in a uniaxial crystal is analysed in terms of Huygens' principle. Then double refraction and double reflection along the sequential interfaces in a crystal are discussed. On this basis, a configuration of electro-optic 1× N optical switch with modulators and birefringent crystal slabs integrated in a single block of crystal is suggested, which is simple and compact in construction, low in loss and insensitive to environment. Finally, calculations are given which lead to a proposed design of a 1×4 switch. [ABSTRACT FROM AUTHOR]

A photorefractive hologram can be fixed locally under a temperature nonuniform field by CO2 laser heating the LiNbO3. Here, on the basis of analyzing the relationship between the fixed space-charge field amplitude Esc and the fixing temperature Tf, two parameters, the localization coefficient Ψ and the average space-charge field amplitude Escave, are defined to evaluate the fixed local photorefractive hologram by CO2 laser heating the LiNbO3. The same analysis also can be used when the boundary conditions and the laser beam profile are changed. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 89–93, 2000. [ABSTRACT FROM AUTHOR]

Based on Moharam's field modulation function and the coupled-wave equations, exact analytic straight and parametric expressions are deduced for the steady state of dynamic two-beam coupling with any constant values of light intensity modulation and light excitation efficiency. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 278–283, 2000. [ABSTRACT FROM AUTHOR]

The transient interaction between a refraction index grating and light beams during simultaneous writing and thermal fixing of a photorefractive hologram is investigated. With a diffusion- and photovoltaic-dominated carrier transport mechanism and carrier thermal activation (temperature dependent) considered in Fe:LiNbO3 crystal, from the standpoint of field–material coupling, the theoretical thermal fixing time and the space-charge field buildup, spatial distribution, and temperature dependence are given numerically by combining the band transport model with mobile ions with the coupled-wave equation. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 372–376, 1999. [ABSTRACT FROM AUTHOR]

In this article we develop a new morphological image processor. In this processor, the input image and interconnection configuration are invariant, and feedback is not necessary. This processor can implement various structuring element morphological image processing functions. It can be implemented by a compact optical weighted interconnection module and the table-lookup threshold technique. Experimental results are also given. [ABSTRACT FROM AUTHOR]

Based on the quadratic residue number system (QRNS), a novel optical matrix-vector multiplication is proposed. Complex number multiplication has higher parallelism than other algorithms. If the residue number is binary encoded, this multiplication can be easily implemented with a multichannel incoherent optical correlator. [ABSTRACT FROM AUTHOR]

The optical set-up for a (2,L) SW-banyan network, which is based on polarizing beam splitters and ID phase spatial light modulators, is proposed and demonstrated, and its corresponding routing control for the routing path between any source-destination pair has been discussed. The proposed optical setup consists of only optical polarization elements, it is compact in structure its corresponding energy loss and cross talk an" low, and its available number of channels is high. [ABSTRACT FROM AUTHOR]

We demonstrate a new approach to achieve optical shuffle interconnection by employing a photorefractive crystal plate in which some required holograms have been recorded and fixed in terms of holographic phase grating. The processes of beam recording, fixing, and reproduction art, described, and an implementation scheme for 1D and 2D shuffle is also proposed. The results of proof-of-principle experiments in one and two dimensions are also presented. [ABSTRACT FROM AUTHOR]

Based on the concept of urea coding, a 2D grayscale morphological processor module is developed by the integration of an optical connector and a PROM device. It is shown that the technique is compact in construction, simple to fabricate, and insensitive to environment. [ABSTRACT FROM AUTHOR]

Based on programmable polarization-optical neighborhood interconnection, which is a stacked integration of rotatable crystal plates for beam splitting the controllable wave plates for polarization direction controlling, a kind of morphological processor with real-time programmable structure elements is developed. It is compact in structure and effective as well as stable in performance. [ABSTRACT FROM AUTHOR]

In this article, one-rule symbolic substitution is introduced to process 2D pattern logic. All the 16 possible logic gates of two input variables are designed. By using a combined system of a multiimaging unit and an optoelectronic morphological unit with two independent input planes of the control pattern and the input patterns, all the logic functions can be achieved by simply programming the control pattern. Experimental results are presented. [ABSTRACT FROM AUTHOR]

The Hartline model is an important neural network model which reveals the lateral inhibition in neural systems. In this article an opto- electronic architecture is proposed for implementing the Hartline model, in which an incoherent optical convolutor is used for the realization of the convolution operation and a polarization-coding method for the representation of the connection weights in the Hartline model. The subtraction is performed by electronics. Preliminary optical edge-enhancement experiments for two-dimensional images illustrate the versatility of the network. [ABSTRACT FROM AUTHOR]

An accumulative recording scheme capable of enhancing diffraction efficiency effectively during nonvolatile holographic storage in LiNbO3:Fe:Mn crystals is proposed and experimentally demonstrated in this paper. The main idea of this new holographic recording schedule is that, during every red-beam recording interval, an ultraviolet light is used to excise more electrons to a shallower center for the next faster and higher recording. After sufficient accumulation of the space-charge fields developed in a deeper center, it is possible to gain a high diffraction efficiency of the finally fixed hologram. The experimental results demonstrate that the finally fixed diffraction efficiency is enhanced by about 31% compared to the conventional recording schedule. No additional equipment is needed in this method, and it has potentials for applications. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 32: 423–425, 2002. [ABSTRACT FROM AUTHOR]

We use a normalized pattern spectrum to construct an image feature vector. In addition, we set up an optical learning vector quantizer to execute real-time image feature vector classification. On the base, shift and rotation-invariant pattern recognition can be achieved. [ABSTRACT FROM AUTHOR]

A new binary-encoded matrix-matrix multiplication architecture based on correlation by shadow casting is presented. It can perform a binary-encoded matrix-matrix multiplication in a fully parallel manner to get the mixed-binary output matrix in the focal plane of the lens. Both the advantages and the disadvantages of the proposed architecture are carefully discussed. The proof-of-principle experiments demonstrate the effectiveness of the proposed architecture. [ABSTRACT FROM AUTHOR]

An optoelectronic architecture is suggested to perform local cellular logic. A polarization coding technique along with the electronic substraction and thresholding techniques are developed to complete the operations with both positive and negative interconnections. Experimental results of the Laplacian operator for edge enhancement and their numerical simulations are given. [ABSTRACT FROM AUTHOR]

Laser beam angular scan accuracy measurement plays an important role in many fields. A sub-microradian laser beam scan precision measurement method that utilizes the wavefront interference method with a Zygo interferometer is proposed. The experimental results show that the measurement accuracy is approximately 0.04 rad, and the new method is very effective and feasible. [ABSTRACT FROM AUTHOR]

A free-space 2 x 4 90º optical hybrid with electro-optic modulation is presented. The hybrid principally consists of two pairs of electro-optic crystal plates coated with gold electrodes and a polarization analyzer. The optical hybrid uses the birefringence effect of a crystal to split and combine a signal beam and a local oscillator beam, uses the electro-optic effect to introduce a phase modulation and produce a phase shift, and outputs four-channel signal/local oscillator mixed beams whose phase difference can be adjusted continuously. A LiNbO3 crystal is used to design and manufacture the space optical hybrid, and an experimental system is used to verify its performance. The results show that the output phase of the hybrid is continuously adjustable, enabling the hybrid to function perfectly as a 2 x 4 90º space optical hybrid under an appropriate electric field, and that the phase error can be compensated for by an electric field adjustment. [ABSTRACT FROM AUTHOR]

The focused visible laser-induced preferential domain nucleation effect is investigated in 3 mol% hafnium-doped congruent lithium niobate crystal. The local phase variation is in-situ monitored during laser-induced preferential domain nucleation. The variations of phase distributions are reconstructed by digital holographic interferometry. The nucleation field decreases exponentially with increasing irradiation intensity. The space charge field along the z direction is thought to be an important mechanism for the laser-induced preferential domain nucleation. Laser-induced hafnium-doped congruent lithium niobate crystals appear to be a promising candidate for further development of ferroelectric domain engineering. [ABSTRACT FROM AUTHOR]

In this Letter we propose complex modular multiplication of two N-bit negabinary complex numbers by adopting digital partitioning and weighting-shifting techniques. The module (-2)N - 1 is introduced for its simple arithmetic. Both complex numbers are treated as two N-bit negabinary real numbers. All four real numbers are decomposed into several short bytes; a corresponding complex product modular (-2)N - 1 is achieved by cyclic convolution. The subtraction in complex multiplication is converted to addition by weighting shifting. The algorithms can be implemented in a fully parallel manner, especially for optics. Both pre- and postprocessing are simple. The proof-of-principle experiment is performed by an incoherent optical correlator, and results are given. [ABSTRACT FROM AUTHOR]

The optical implementations of a 2-D neural net with a third-order interconnection for image quadratic associative memory are reported. Two types of incoherent optical systems, based on multiple imaging and correlation, are used. In particular, a compact-encoding method, which can greatly reduce the size of the interconnection tensor, is also proposed. The experimental results are given. [ABSTRACT FROM AUTHOR]

The availability and reliability of the high data rate space-to-ground optical coherent communication links are critically challenged because the wave front of the signal beam is distorted and impaired when propagating through atmospheric turbulence. Based on the free-space interference of two successive data bits delayed by an unequal-arm-length Mach-Zehnder interferometer (MZI), a pupil-matching time-delay self-homodyne interference differential phase-shift keying (DPSK) optical receiver with 2 × 4 90-deg optical hybrid is designed for the high data rate space-to-ground optical communication links due to its immunity from wave front impairment. The delayed optical path difference (OPD) in the unequal-arm-length MZI corresponds to the duration of one bit and can be stabilized to below 1000th of the wavelength by the closed-loop feedback control. The maximum system insertion loss is <1 dB. The measurement accuracy of OPD in unequal-armlength MZI is 0.01 mm by the deramping method from a chirped laser. The double-bit-rate 2.5-/5-Gbps DPSK optical receiver has been presented. Parallel and separate atmospheric measurement along the optical communication link is also performed simultaneously. The 2.5-and 5-Gbps optical communication links have already been verified with a ϕ300-mm receiving telescope between two buildings in downtown over a distance of 2.4 km in the worst-case atmospheric conditions. The measured bit-error-rate is better than 10-6. Without wave front compensation of the adaptive optics, local oscillator, and optical phase-locked loops, the pupil-matching time-delay self-homodyne interference DPSK optical receiver has great significance for future developments of space-to-ground optical communication links. [ABSTRACT FROM AUTHOR]

A strip-mode side-looking large-aperture synthetic aperture imaging ladar (SAIL) based on freespace optics is designed to experimentally verify the key performances for further airborne application. The optical difficulties in the spatial domain, including optical antenna and imaging resolution for large-aperture SAIL, are considered systematically. The optical antenna consists of a circulated duplex including the tunable transmission and reception channels for the flexible wavefront control. An irradiating beam with a spatial quadratic phase-bias for the suitable and controlled phase history can be transmitted from the transmission channel, and the wavefront aberration in the reception channel resulted from the diffraction can be eliminated for the optimized heterodyne detection. The construction and 2-D imaging algorithm of the SAIL are also proposed. The performances, including wavefront, heterodyne efficiency, field of view, imaging resolution, and 2-D imaging algorithm, have been systemically verified in the short-distance of laboratory space. The well-focused 2-D SAIL imaging of a diffusely scattering target with submillimeter imaging resolution is given. The experimental results are in good agreement with the theoretical design. The results have the great significance for the future development of airborne large-aperture SAIL. [ABSTRACT FROM AUTHOR]

Hypopharynx carcinoma tends to be diagnosed at advanced stage and usually has a poor prognosis because of the high incidence of submucosal spreading and lymphatic metastasis. Total pharyngolaryngoesophagectomy (PLE) is mostly used as a curative intervention for this deadly disease, and a commonly used reconstruction method after PLE is gastric pull-up, which could be further divided into tubular gastric pull-up and whole gastric pull-up procedures. Aiming to achieve a precise guidance on optimal reconstruction method after PLE, the present study evaluated the postoperative complications involving in different gastric pull-up procedures in patients with hypopharynx cancer. A total of 52 consecutive patients with hypopharyngeal cancer who underwent total PLE with gastric pull-up reconstruction in Tianjin Medical University Cancer Institute and Hospital between 1996 and 2014 were analyzed in this study. Of these patients, 28 underwent tubular gastric pull-up reconstruction procedure (Group A), whereas 24 underwent whole gastric pull-up reconstruction procedure (Group B). We compared the postoperative complications between these two groups retrospectively. Postoperative anastomotic fistulas occurred in three patients in Group A (3/28) versus eight patients in Group B (8/24), leading to an incidence rate of 10.71 and 33.33 per cent, respectively. The incidence of intrathoracic stomach syndrome was 21.43 per cent in Group A (6/28) versus 58.33 per cent in Group B (14/24), and the incidence of reflux was 35.71 per cent in Group A (10/28) versus 66.67 per cent in Group B (16/24). All of the above postoperative complications exhibited statistical differences between two groups (P ≤ 0.05). This retrospective observation study suggests that compared with whole gastric pull-up, tubular gastric pull-up is a better reconstruction procedure of choice after PLE, evidenced by reduced incidences of postoperative anastomotic fistula, intrathoracic stomach syndrome, and reflux. [ABSTRACT FROM AUTHOR]

Controlling the bimetal nanoparticle with atomic monodispersity is still challenging. Herein, a monodisperse bimetal nanoparticle is synthesized in 25% yield (on gold atom basis) by an unusual replacement method. The formula of the nanoparticle is determined to be Au24Hg1(PET)18 (PET: phenylethanethiolate) by high-resolution ESI-MS spectrometry in conjunction with multiple analyses including X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). X-ray single-crystal diffraction reveals that the structure of Au24Hg1(PET)18 remains the structural framework of Au25(PET)18 with one of the outer-shell gold atoms replaced by one Hg atom, which is further supported by theoretical calculations and experimental results as well. Importantly, differential pulse voltammetry (DPV) is first employed to estimate the highest occupied molecular orbit (HOMO) and the lowest unoccupied molecular orbit (LUMO) energies of Au24Hg1(PET)18 based on previous calculations. [ABSTRACT FROM AUTHOR]

Based on dual-rail spatial coding, in this article a self-programming optical logic concept is proposed. The self-programming is formulated by different coding of input images. Thus all 16 binary logic operations can be realized optically in parallel. Experimental results are demonstrated. [ABSTRACT FROM AUTHOR]

Direct transduction of the homeobox (HOX) protein HOXB4 promotes the proliferation of hematopoietic stem cells (HSCs) without induction of leukemogenesis, but requires frequent administration to overcome its short protein half-life (~1 hour). We demonstrate here that HOXB4 protein levels are post-translationally regulated by the CUL4 ubiquitin ligase, and define the degradation signal sequence (degron) of HOXB4 required for CUL4-mediated destruction. Additional HOX paralogs share the conserved degron in the homeodomain and are also subject to CUL4-mediated degradation, indicating that CUL4 likely controls the stability of all HOX proteins. Moreover, we engineered a degradation-resistant HOXB4 that conferred a growth advantage over wild-type HOXB4 in myeloid progenitor cells. Direct transduction of recombinant degradation-resistant HOXB4 protein to human adult HSCs significantly enhanced their maintenance in a more primitive state both in vitro and in transplanted NOD/SCID/ IL2R-γnull mice compared with transduction with wild-type HOXB4 protein. Our studies demonstrate the feasibility of engineering a stable HOXB4 variant to overcome a major technical hurdle in the ex vivo expansion of adult HSCs and early progenitors for human therapeutic use. [ABSTRACT FROM AUTHOR]

By the finite element analysis method, the deformation and stress of the double-shearing mirror assembly is studied to validate the feasibility of the opto-mechanical structure. The side axial deformations (within ∅400 mm) of the upper semicircular mirror and the lower one are both up to micrometer order along the Y-direction under gravitational action. The equivalent stresses of two semicircular mirrors are more concentrated in the contact areas, but far less than the admissible stress of K9 material. The axial deformations of double-shearing mirror surfaces induced by the temperature rise are very serious, which are the major error sources for the measurement accuracy. The experimental results further validate the analysis conclusions available and show the opto-mechanical design to be reasonable. [ABSTRACT FROM AUTHOR]

The Talbot effect of a grating under ultrashort short-pulsed light illumination is analyzed from its Fresnel diffraction equation. We find that the Talbot self-imaging effect gradually diminishes when the full width Δτ at half maximum of the incident ultrashort laser pulse decreases. If Δτ is within a few tens of femtoseconds, the self-imaging effect disappears. We note that the maximal value of the sharp peak of the intensity distribution at the first Talbot distance increases steadily along with the increase of Δτ. Therefore, by using this phenomenon, the width of an ultrashort laser pulse can be measured roughly. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 184–187, 2000. [ABSTRACT FROM AUTHOR]

A compact packaging optical crossbar network is proposed in the article. It is based on a polarization multiplex technique. This compact packaging crossbar network is easy to assemble and insensitive to environmental disturbance. We also construct an optical HIPPI interconnection system. [ABSTRACT FROM AUTHOR]

The primary and secondary threshold intensities of ultraviolet-laser-induced preferential domain nucleation in nearly stoichiometric LiTaO3 is observed. The primary threshold is the minimum intensity to achieve the instantaneous preferential domain nucleation within the focus by the combined action of irradiation and electric fields. The secondary threshold is the minimum intensity to achieve the memory effect without any irradiation within the original focus. The space charge field created by the photoionization carriers is thought to be responsible for the instantaneous effect. The explanation based on the formation and transformation of extrinsic defect is presented for the memory effect. [ABSTRACT FROM AUTHOR]

The phase contrast across the crystal thickness induced by the internal field is measured by the digital holographic interferometry just after the congruent lithium niobate crystal is partially poled. The direction of applied external field is antiparallel to that of internal field, and the measured phase contrast varies linearly with the applied external field. A new internal field is obtained by this method and named effective internal field. The distinct discrepancy between effective and equivalent internal fields is observed. The authors attribute this effect to the new macroscopic representation of elastic dipole components of defect complex in the crystal. [ABSTRACT FROM AUTHOR]

The digital holographic interferometry is used in the dynamic and static measurements of phase variation induced by domain inversion. For the first time, to the authors' knowledge, they observe the existence of ridge-shape phase distribution adjacent to 180° domain wall in congruent LiNbO3 crystal. During the domain wall motion, the phase variations are not uniform but have obvious relaxations. In the static measurement, the ridge elevation can vary linearly with the uniform electric field. The reasonable assumptions are proposed to explain these effects. [ABSTRACT FROM AUTHOR]

A reversible electrochromic effect during the electrical poling process in LiNbO3:Ru:Fe crystals at room temperature is observed. In electrode area, both electrochromism and domain-inversion occur mutually and electrochromism is reversible during back-switch poling, which are experimentally verified, and a microstructure model to explain the mechanism is proposed. In addition, different from the undoped LiNbO3 crystals, the breakdown field (>25.0 kV/mm) is higher than the coercive (21.0 kV/mm) measured in LiNbO3:Ru:Fe, which proves a possible new technique to realize domain-inversion by constant electric field rather than pulsed one. [ABSTRACT FROM AUTHOR]

An optical 90-deg hybrid of birefringent crystals for freely propagating laser beams is presented. It consists principally of a quarter-wave plate, two pairs of birefringent crystal plates, and a polarization analyzer. The splitting and recombination of the signal and local-oscillator beams are achieved through the birefringence of the crystals, and a 90-deg phase shift is introduced between orthogonally polarized beam components by use of a quarter-wave plate. The optical hybrid has a self-compensating light path, and its correct function is demonstrated in a self-heterodyne measurement setup. [ABSTRACT FROM AUTHOR]

The self-enhancement and self-depletion phenomena originated from the beam-coupling effect are observed during both the recording and fixing phases in LiNbO[sub 3]:Fe:Mn nonvolatile holographic storage experiments. A numerical simulation and a steady-state analysis are developed to provide a mathematical evaluation to the phenomena. From the experimental and theoretical studies, it is seen that the highest diffraction efficiency available from the self-enhancement may be twice as large as the lowest one from the self-depletion, both during the recording and fixing phases. Therefore, the use of the self-enhancement is necessary for the practical applications. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]