Influence of Misalignment on High-Order Aberration Correction for Normal Human Eyes

Although a compensation device can correct aberrations of human eyes, the effect will be degraded by its misalignment, especially for high-order aberration correction. We calculate the positioning tolerance of correction device for high-order aberrations, and within what degree the correcting effect is better than low-order aberration （defocus and astigmatism） correction. With fixed certain misalignment within the positioning tolerance, we calculate the residual wavefront rms aberration of the first-6 to first-35 terms along with the 3rd-Sth terms of aberrations corrected, and the combined first-13 terms of aberrations are also studied under the same quantity of misalignment. However, the correction effect of high-order aberrations does not meliorate along with the increase of the high-order terms under some misalignment, moreover, some simple combined terms correction can achieve similar result as complex combinations. These results suggest that it is unnecessary to correct too much the terms of high-order aberrations which are difficult to accomplish in practice, and gives confidence to correct high-order aberrations out of the laboratory.     

Measurements of AIM for Visible Wavelength Based on Individual Eye Model

We measure and calculate the aerial image modulation （AIM） of human retina for visible wavelengths based on the individual eye model. By employing the optical design software ZEMAX, we obtain the modulation transfer function （MTF） of human eye in visible wavelengths. Using CSV-1000 and VAF-1000, the contrast sensitivity function （CSF） and the visual acuity （VA） for the same eye are measured. Then the AIM of human retina could be acquired by the relations between MTF and CSF and between MTF and VA. The AIM of human retina is independent of MTF, and the values of AIM for normal eyes （without retina disease） are similar, so the assembly average for large numbers of normal eyes can be a standard AIM curve, which is helpful for the diagnosis of diseases in the retina system.     

Correlation between Post-LASIK Starburst Symptom and Ocular Wavefront Aberrations

Monochromatic aberrations in post laser in-situ keratomileusis （LASIK） eyes are measured. The data are categorized into reference group and starburst group according to the visual symptoms. Statistic analysis has been made to find the correlation between the ocular wavefront aberrations and the starburst symptom. The rms aberrations of the 3rd and 4th orders for the starburst group are significantly larger than those for the reference group. The starburst symptom shows a strong correlation with vertical coma, total coma, spherical aberrations. For 3-mm pupil size and 5.8-mm pupil size, the modulation transfer function （MTF） of the starburst group are lower than those of the reference group, but their visual acuities are close. MTF and PSF analyses are made for two groups, and the results are consistent with the statistical analysis, which means the difference between the two groups is mainly due to the third- and fourth-order Zernike aberrations.     

Measurements of Absorption and Anisotropy Coefficients of the Fat Emulsion Intralipid-10%

We report measurements of absorption and anisotropy coefficients of the fat emulsion Intralipid-10%. An addingabsorber method is used for measurement of absorption and anisotropy coefficients of the Intralipid-10%. Using the diffusion theory which has been extended to include anisotropy scat geometry, we found that the standard deviations of multiple measurements for√μα/D are less than 0.6% and the residuals between the measured data and the fits have rms values of 0.1%, where μα is the absorbing coefficient of the solution in our experiment and D is the diffusion coefficient of the medium. The values of the standard deviations and the residuals demonstrate the high precision of the measurements.     

Optical color image encryption based on Arnold transform and interference method

In this paper, we propose a novel method to encrypt a color image based on Arnold transform (ART) and interference method. A color image is decomposed into three independent channels, i.e., red, green and blue, and each channel is then encrypted into two random phase masks based on the ART and interference method. Light sources with corresponding wavelengths are used to illuminate the retrieved phase-only masks during image decryption. The influence of security parameters on decrypted images is also analyzed. Numerical simulation results are presented to illustrate the feasibility and effectiveness of the proposed method.     

Contrast Adaptation Decreases Complexity in Retinal Ganglion Cell Spike Train

The difference in temporal structures of retinal ganglion cell spike trains between spontaneous activity and firing activity after contrast adaptation is investigated. The Lempel-Ziv complexity analysis reveals that the complexity of the neural spike train decreases after contrast adaptation. This implies that the behaviour of the neuron becomes ordered, which may carry relevant information about the external stimulus. Thus, during the neuron activity after contrast adaptation, external information could be encoded in forms of some certain patterns in the temporal structure of spike train that is significantly different, compared to that of the spike train during spontaneous activity, although the firing rates in spontaneous activity and firing activity after contrast adaptation are sometime similar.     

Temporal and spectral properties of picosecond two-photon pumped cavity lasing of an organic dye HEASPS

The operation of cavity lasing of a two-photon absorption (TPA) organic dye, trans-4-[p-(N-hydroxyethyl-N-ethylamino)styryl]-N-methylpyridinium p-toluene sulfonate (abbreviated as HEASPS), by using a picosecond infrared laser as the pump source, is reported. The lifetimes of TPA fluorescence of this dye in different solvents were measured. Temporal profiles of cavity lasing show obvious oscillations and magnification of the feedback light. By using the difference of re-absorption coefficients at different conditions, we explained the blue shift for cavity lasing and superradiance compared with TPA-induced fluorescence. The long lifetime of fluorescence is helpful to the generation of cavity lasing. Received: 18 June 2001 / Revised version: 5 November 2001 / Published online: 17 January 2002     

Diffuse Backscattering Mueller Matrices Patterns from Turbid Media

We present experimental measurements and theory of the diffusely backscattered Mueller matrix patterns that arise from illuminating a turbid medium with a polarized laser beam. Our technique employs polarized light from a He-Ne laser (λ=632.8nm) focused onto the surface of the scattering medium. A surface area of approximately 2×2 cm² centred on the light input point is imaged through polarization analysis optics onto a CCD camera. The Mueller matrix is reconstructed by 49 intensity measurements with various orientations of polarizer and analyser. The measured Mueller matrix of polystyrene spheres is compared with the theory result of incoherent scattering of light by spheres. It shows that the azimuthal patterns of the Mueller matrix are determined by the symmetry of the turbid media and the shape of scattering particles. The result is further proved by experiments with polystyrene spheres of different concentrations in de-ionized water.     

Photo-thermal Shot Noise in End Mirrors of LIGO due to Correlation of Power Fluctuation

The effect of input power fluctuation on photo-thermal shot noise in the end mirrors of a laser interferometer gravitational-wave observatory （LIGO） is analysed according to the statistical optics, which is a supplement of Braginsky＇s research. The laser light folding in LIGO increases a correlation of input power fluctuation in the photo-thermal shot noise. This part of noise has spectral density proportional to -2 in low frequency bands, and -4 in high frequency bands. It is not a white noise and may affect the processing about data of interferometers. To obtain an advanced LIGO, photo-thermal shot noise in end mirrors due to correlation of input power fluctuation is up to Braginsky＇s photo-thermal noise in the frequency range 1-100 Hz.     

Instability of Solution of Phase Retrieval in Direct Diffraction Phase-Contrast Imaging with Partially Coherent X-Ray Source

The theoretical model of direct diffraction phase-contrast imaging with partially coherent x-ray source is expressed by an operator of multiple integral. It is presented that the integral operator is linear. The problem of its phase retrieval is described by solving an operator equation of multiple integral. It is demonstrated that the solution of the phase retrieval is unstable. The numerical simulation is performed and the result validates that the solution of the phase retrieval is unstable.     

Chemical Potential Dependence of Two-Quark Condensates

By adopting the background field method, the response of the dressed quark propagator to the presence of finite chemical potential is analysed up to the second order. From this, we obtain a model-independent formula for the chemical potential dependence （up to the second order） of the in-medium two-quark condensate and show by both Lorentz covariance arguments and explicit calculations that the O（μ） contribution to the in-medium two-quark condensate vanishes identically.     

Exact Timing of Returned Molecular Wavepacket

An ionizing wavepacket of electron will re-visit its parent molecular ion during photoionization by strong laser field. This scenario is associated with physical concepts such as molecular re-scattering/collision, interference, diffraction, molecular clock, and generation of XUV light via high-order harmonic generation. On the workbench of a reduced dimensionality model of molecular hydrogen ions irradiated by laser pulse of 0.01-10.0 a.u. intensities, one-cycle pulsewidth, and 800nm wavelength, by deploying a momentum operator on the time-dependent wavefunction of an ionizing wavepacket, we can determine, in a precise manner, the exact time instant for the re-visiting electron to come back to the cation position. The time value is 57.6% of an optical cycle of the exciting laser pulse. This result may be useful in attosecond pump-probe experiments or molecular clock applications.     

The Genesis of Physics at the Hebrew University of Jerusalem

The creation of a good physics department in the newly established Hebrew University in Jerusalem (opened in 1925) was an important goal for Chaim Weizmann, President of the Zionist Organization and founder of the University (and chemist, by profession). A. H. Fraenkel, the mathematician, and L. S. Ornstein, the physicist from Utrecht, invested a lot of effort in achieving this goal. Albert Einstein was consulted on an almost day-to-day basis. Serious attempts were made to bring a first-rate theoretician to Jerusalem. After 1933, the chances for getting such a physicist were actually very good. George Placzek worked in Jerusalem during the academic year 1934–1935. Felix Bloch, Eugene Wigner, and Fritz London were offered positions as theoretical physicists in Jerusalem and considered the offers favorably. The discussions and correspondence with these great physicists are illuminating. Budget limitations, the problem of the teaching language (Hebrew) and the seclusion of Jerusalem from science centers in Europe or the United States undermined all these efforts. A solution was found when Giulio Racah from Italy finally was appointed.     

Macro-Behaviour of Agents＇ Opinion under Influence of an External Field

We propose a model to study the evolution of opinion under the influence of all external field on small world network. The maero-behaviour of agents＇ opinion and the relative change rate as time elapses are studied. The external field is found to play an important role in making the opinion s（t） balance or increase, and without the influence of the external field, the relative change rate γ（t） shows nonlinear increasing behaviour as time runs. What is more, this nonlinear increasing behaviour is independent of the initial condition, the strength of the external field and the time that we cancel the external field. The results may reflect some phenomena in our society, such as the function of the macro-control in China or the mass media in our society.     

The effect of Ehrlich-Schwoebel step-edge barrier on the formation of self-organized Si nanodots by ion-sputter erosion

The ion flux dependence of the self-organized Si nanodots induced by 1.5 keV Ar⁺ ion sputter erosion has been studied. It shows that for the regime with ion flux >∼280 μA/cm², the currently adopted Bradley-Harper (BH) model, which is incorporated in a dynamic continuum equation holds valid. However, for ion flux <∼280 μA/cm², the measured dot size and surface roughness deviate drastically from the BH model. To interpret the data for this lower ion flux regime, the effect of the Ehrlich-Schwoebel (ES) step-edge barrier was introduced into the continuum equation. A consistency between the calculated and the experimental results was reached, furthermore, a reasonable trend was found, that is, the effective ES diffusion decreases steadily with the increasing ion flux, and at ∼280 μA/cm², it became negligibly small.     

Fisher Information of Wavefunctions： Classical and Quantum

A parametric quantum mechanical wavefunction naturally induces parametric probability distributions by taking absolute square, and we can consider its classical Fisher information. On the other hand, it also induces parametric rank-one projections which may be viewed as density operators, and we can talk about its quantum Fisher information. Among many versions of quantum Fisher information, there are two prominent ones. The first, defined via a quantum score function, was introduced by Helstrom in 1967 and is well known. The second, defined via the square root of the density operator, has its origin in the skew information introduced by Wigner and Yanase in 1963 and remains relatively unnoticed. This study is devoted to investigating the relationships between the classical Fisher information and these two versions of quantum Fisher information for wavefunctions. It is shown that the two versions of quantum Fisher information differ by a factor 2 and that they dominate the classical Fisher information. The non-coincidence of these two versions of quantum Fisher information may be interpreted as a manifestation of quantum discord. We further calculate the difference between the Helstrom quantum Fisher information and the classical Fisher information, and show that it is precisely the instantaneous phase fluctuation of the wavefunctions.     

Micro-Photoluminescence Confocal Mapping of Single V-Grooved GaAs Quantum Wire

We perform the micro-photoluminescence measurement at low temperatures and a scanning optical mapping with high spatial resolution of a single V-grooved GaAs quantum wire modified by the selective ion-implantation and rapid thermally annealing. While the mapping shows the luminescences respectively from the quantum wires and from quantum well areas between quantum wires in general, the micro-photoluminescence at liquid He temperatures reveals a plenty of spectral structures of the PL band for a single quantum wire. The spectral structures are attributed to the inhomogeneity and non-uniformity of both the space structure and compositions of real wires as well as the defects nearby the interface between quantum wire and surrounding quantum well structures. All these make the excitons farther localized in quasi-zero-dimensional quantum potential boxes related to these non-uniformity and/or defects. The results also demonstrate the ability of micro-photoluminescence measurement and mapping for the characterization of both opto-electronic and structural properties of real quantum wires.     

How to Define the Equality of Durations in Measurement of Time

We develop the research on measurement of time worked by Poincarh, Einstein, Landau and other researchers. Based on the convention that the velocity of light is isotropic and is a constant in empty spacetime, we not only answer the question about the definition of the synchronization of rate of clocks located at different places, but also find the solution to the issue of how to define the equality of two durations in measurement of time.     

A Complete Foliation of Schwarzschild Spacetime by Free Falling Hypersurfaces

Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete foliation of spacetime. The hypersurfaces do not cross into the maximally extended spacetime and are well behaved everywhere except at the singularity r =0 the mean extrinsic curvature becomes infinity.