Controlling an optical vortex array from a vortex phase plate, mode converter, and spatial light modulator.

In this Letter, we propose a convenient method of generating an optical vortex (OV) array, in which the size and quantity can be controlled by employing vortex phase plates, a mode converter, and a spatial light modulator into a simple optical system. Different sizes of OV arrays are generated from the superposition of crossed Hermite-Gaussian (HG) modes possessing equal or unequal orders and mutually orthogonal circular polarizations. We experimentally and theoretically demonstrate a series of vector superposed optical fields. Here the sizes of the OV arrays, as well as the quantities of OVs, are defined in terms of specific sets of HG bases. Our results indicate that a simple setup can be used to effectively generate and control OVs and OV arrays.

Kaleidoscope vortex lasers generated from astigmatic cavities with longitudinal-transverse coupling.

We propose an efficient and robust method to generate the kaleidoscope vortex beam by employing an astigmatic laser cavity with an extra-cavity cylindrical lens. The kaleidoscope vortex beam is arising from the superposition of Laguerre-Gaussian modes with the longitudinal-transverse coupling effect in the laser cavity. The superposed Laguerre-Gaussian mode leads to the formation of complex phase singularities and implies the participation of different optical orbital angular momentum involved in a single kaleidoscope vortex beam. We experimentally demonstrate that a series of kaleidoscope vortex beams with different symmetry are systematically achieved by using a simple setup. The output power of the laser is dependent on the cavity length. This approach is expected to create high-order optical vortex beams and pave the way for optical entanglement.

Exploring vortex structures in orbital-angular-momentum beams generated from planar geometric modes with a mode converter.

It is theoretically demonstrated that the planar geometric mode with a π/2 mode converter, so called the circularly geometric mode, can be solved from the inhomogeneous Helmholtz equation by considering the pump distribution on the lasing mode. Theoretical analysis clearly reveal that the vortex structures of circularly geometric modes are determined by the minimum order of transverse lasing modes, the total number of transverse lasing modes and the degenerate condition in the cavity. Moreover, we experimentally manifest that the circularly geometric mode can be generated from the selective pumped solid-state laser with an external π/2 mode converter. To explore the vortex structures of the generated geometric modes, the interference patterns are performed by an experimental apparatus consisting of a Mach-Zehnder interferometer. The good agreement between experimental observations and numerical calculations confirms the analysis of vortex structures is reliable.

Generating orthogonally circular polarized states embedded in nonplanar geometric beams.

We experimentally demonstrated the generation of orthogonally circular polarized states embedded in nonplanar geometric beams. Experimental results revealed that the production of circularly polarized beams, induced by crystal birefringence, is quantized. Numerical analyses of the polarization and the spatial morphology are consistent with the experimental results.

Observation and analysis of single and multiple high-order Laguerre-Gaussian beams generated from a hemi-cylindrical cavity with general astigmatism.

We experimentally verified that anisotropic Hermite-Gaussian modes can be generated from a hemi-cylindrical laser cavity and can be transformed into high-order Laguerre-Gaussian modes using an extra-cavity cylindrical lens. We further combined the Huygens integral and the ABCD law to clearly demonstrate the transformation along the propagation direction. By controlling the pump offset and the pump size in hemi-cylindrical cavities, we experimentally observed the unique laser patterns that displayed the optical waves related to the coherent superposition of Laguerre-Gaussian modes.

Generation of optical vortex array with transformation of standing-wave Laguerre-Gaussian mode.

We develop a novel method of creating optical vortex array by the conversion of a standing-wave Laguerre-Gaussian (LG) mode. Theoretically, by employing the transformational relation, the standing-wave LG mode is verified to be transformed from a pair of crisscrossed Hermite-Gaussian (HG) modes, embedded with optical vortex array, consists of a TEMn,m mode and a TEMm,n mode. Due to close correspondence between the transformational relation and the mode conversion of astigmatic lenses, we successfully generate the optical vortex array by transforming a standing-wave LG mode into the crisscrossed HG modes via a π/2 cylindrical lens mode converter. The investigation may provide useful insight in the study of the vortex light beam and its further applications.

The effects of falls on the prediction of osteoporotic fractures: epidemiological cohort study.

Fall is the major risk factor of fracture that has not been included in FRAX®. Whether different age may determine the effect of falls on FRAX® is still uncertain. This epidemiological cohort study reveals that history of fall is a significant predictor of incident fracture independent of FRAX probability, especially in subjects < 75 years old. INTRODUCTION: The Fracture Risk Assessment Tool (FRAX) calculates 10-year fracture risk using 11 clinical risk factors and bone mineral density (BMD); however, it does not include fall history in its risk assessment. Here, we investigated whether fall history is an independent risk factor on fracture prediction after adjustment of FRAX scores in two age subgroups (40-75 and ≥ 75 years). METHODS: Beginning in 2009 to 2010, 1975 people (914 men) from Taiwan were followed for 6.8 ± 1.1 years by matching them with their records in the 2008-2016 National Health Insurance databank. We validated FRAX predictive accuracy with or without fall history by Cox proportional hazards regression. RESULTS: After adjusting for FRAX risk, a history of falling was still a significant predictor of major osteoporotic fractures (MOFs) (using BMD, hazard ratio [HR], 1.47; p = 0.03; without using BMD, HR, 1.54; p = 0.01). A history of recurrent falls was also a significant predictor of both incident MOFs and hip fractures. However, when the subjects were stratified based on age group, a history of falling and recurrent falls were strong predictors of MOFs and hip fractures in the younger but not the older subgroup. CONCLUSION: A fall history can predict incident fracture independently of FRAX probability, particularly in subjects younger than 75 years old.

Observation of lasing modes with exotic localized wave patterns from astigmatic large-Fresnel-number cavities.

We investigate the lasing modes in large-Fresnel-number laser systems with astigmatism effects. Experimental results reveal that numerous lasing modes are concentrated on exotic patterns corresponding to intriguing geometries. We theoretically use the quantum operator algebra to construct the wave representation for manifesting the origin of the localized wave patterns.

Electronic and transport properties of a molecular junction with asymmetric contacts.

Asymmetric molecular junctions have been shown experimentally to exhibit a dual-conductance transport property with a pulse-like current-voltage characteristic, by Reed and co-workers. Using a recently developed first-principles integrated piecewise thermal equilibrium current calculation method and a gold-benzene-1-olate-4-thiolate-gold model molecular junction, this unusual transport property has been reproduced. Analysis of the electrostatics and the electronic structure reveals that the high-current state results from subtle bias induced charge transfer at the electrode-molecule contacts that raises molecular orbital energies and enhances the current-contributing molecular density of states and the probabilities of resonance tunneling of conduction electrons from one electrode to another.

Adverse birth outcomes among pregnancies of teen mothers: age-specific analysis of national data in Taiwan.

BACKGROUND: This study was conducted to evaluate the risks of adverse birth outcomes including low birthweight, preterm and small-for-gestational age among teen mothers. METHODS: Data were collected from the Taiwan Birth Registry between 1985 and 1997. Among a total of 1,185,597 live births born to mothers aged 24 years or less, 151,259 (12.8%) were born to teen mothers aged 19 years or less. Crude odds ratios (ORs), adjusted ORs (AORs), their 95% confidence intervals and test for linear trend of maternal age-specific AOR were estimated using logistic regression analysis. RESULTS: After controlling for certain birth characteristics and socio-economic factors, the age-specific analysis showed significantly gradient variations in increased risks of adverse birth outcomes among births of teen mothers, where the elevated risk was lessened in older teen mothers. Teen mothers aged 16 years or less were observed to experience particularly high AORs for all adverse birth outcomes of interest. CONCLUSIONS: Not all teen mothers experienced the same magnitude of increased risk of adverse birth outcomes in Taiwan. Considering all teen mothers as the same group may have overlooked the particularly high risks of adverse birth outcomes among very young teen mothers (16 years or less), who are especially vulnerable to such elevated risks.

Observation and analysis of coherent optical waves emitted from large-Fresnel number degenerate cavities.

We demonstrate that the coherent optical waves emitted from large-Fresnel-number degenerate cavities persistently display a sort of salient intensity variations. We use the representation of the coherent states to explore the origin of the salient intensity variations and find that these coherent laser waves arise from a quadrature superposition of two degenerate coherent states. With the analytical representation of the superposed coherent states, we verify that these coherent laser waves possess a large angular momentum per photon.

Picosecond optical vortex converted from multigigahertz self-mode-locked high-order Hermite-Gaussian Nd:GdVO(4) lasers.

We report on a gigahertz self-mode-locked high-order Hermite-Gaussian (HG) Nd:GdVO(4) laser. With a pump power of 2.2 W, the average output power for the TEM(0,m) modes from m=9 to m=0 are among 350-780 mW at a repetition rate of 3.5 GHz. The mode-locked pulse width is in the range of 20-25 ps for various HG TEM(0,m) modes. With a simple cylindrical-lens converter, the mode-locked HG beams are converted to generate picosecond optical vortex pulses.

Ponticulin is an atypical membrane protein.

We have cloned and sequenced ponticulin, a 17,000-dalton integral membrane glycoprotein that binds F-actin and nucleates actin assembly. A single copy gene encodes a developmentally regulated message that is high during growth and early development, but drops precipitously during cell streaming at approximately 8 h of development. The deduced amino acid sequence predicts a protein with a cleaved NH2-terminal signal sequence and a COOH-terminal glycosyl anchor. These predictions are supported by amino acid sequencing of mature ponticulin and metabolic labeling with glycosyl anchor components. Although no alpha-helical membrane-spanning domains are apparent, several hydrophobic and/or sided beta-strands, each long enough to traverse the membrane, are predicted. Although its location on the primary sequence is unclear, an intracellular domain is indicated by the existence of a discontinuous epitope that is accessible to antibody in plasma membranes and permeabilized cells, but not in intact cells. Such a cytoplasmically oriented domain also is required for the demonstrated role of ponticulin in binding actin to the plasma membrane in vivo and in vitro (Hitt, A. L., J. H. Hartwig, and E. J. Luna. 1994. Ponticulin is the major high affinity link between the plasma membrane and the cortical actin network in Dictyostelium. J. Cell Biol. 126:1433-1444). Thus, ponticulin apparently represents a new category of integral membrane proteins that consists of proteins with both a glycosyl anchor and membrane-spanning peptide domain(s).

Descriptive epidemiological study of sites of suicide jumps in Taipei, Taiwan.

OBJECTIVE: To identify locations to target for suicide preventive measures to reduce suicide by jumping in Taipei city, Taiwan. METHOD: A descriptive study of suicide by jumping from a height was conducted in Taipei, 2002-2005. Information on sites from which suicide jumps occurred was obtained from death certificates as well as ambulance, medical and newspaper records. RESULTS: Of the 210 jumping suicide deaths with sufficient information on the site of the jump, private residential buildings comprised the highest proportion (67%) of all jumping sites, followed by business office buildings (13%), hospitals (8%) and shopping malls (5%). However, the number of jumping suicides per 1000 sites was highest for hospitals (307 per 1000 hospitals) and shopping malls (275 per 1000 shopping malls) compared with 2 per 1000 for residential buildings. Women and older people who died by jumping were more likely to have jumped from buildings where they lived, compared with men and other age groups. CONCLUSION: Although two-thirds of suicides occurred from residential buildings, the sites with the greatest number of jumps per location were hospitals and shopping malls, making them the most cost-effective focus for preventive efforts.

Generation of polarization-entangled optical coherent waves and manifestation of vector singularity patterns.

We use a high-level isotropic laser with off-axis focused and on-axis circular pumping to generate the high order polarization-entangled transverse modes. The main finding is that the complex transverse modes can be categorized into four types: square pattern, hyperbolic pattern, elliptic pattern, and circular pattern. Importantly, all types of the polarization-entangled modes can be well analyzed with the generalized coherent states. With the connection between theoretical analysis and experimental results, the formation of complex singularities can be clearly represented.

Generation of two-dimensional chaotic vector fields from a surface-emitting semiconductor laser: analysis of vector singularities.

We demonstrate experimental generation of two-dimensional (2D) chaotic vector fields from a surface-emitting microcavity laser with precisely control of the operating temperature and the operating current. The 2D optical vector field is found to be formed by frequency locking of two linearly polarized laser modes with different chaotic spatial structures. The eigenfunction expansion method is used to reconstruct the experimental wave function for analyzing the properties of the vector singularities. It is shown that the distribution of vector singularities obeys the sign rule of nearest-neighbor singularities in the phase space of the vector field.

Statistical properties of experimental coherent waves in microcavity lasers: analogous study of quantum billiard wave functions.

We use a microcavity laser to explore the properties of experimental coherent waves as an analogous study of the chaotic wave functions in quantum billiards. With the eigenstate expansion method, the experimental high-order chaotic coherent waves are well reconstructed. The reconstructed wave functions are employed to calculate the field and intensity correlations. It is found that the spreading of k-space (momentum space) distribution leads to not only wave localization in coordinate space but also enhancement of long-range correlations.

Wave functions with localizations on classical periodic orbits in weakly perturbed quantum billiards.

We analytically investigate quantum wave functions with localizations on classical periodic orbits (POs) in the circular billiards. We construct the coherent states which are the coherent superpositions of nearly degenerate eigenstates and found to be localized around single classical POs. With the constructed coherent states, we can analytically express the mesoscopic eigenstates in the weakly perturbed systems, which are found to be localized on the ensemble of classical POs. Furthermore, these coherent states can be utilized to study the quantum vortex structures in quantum billiards.

Generation of flower high-order Poincaré sphere laser beams from a spatial light modulator.

We propose and experimentally demonstrate a new complex laser beam with inhomogeneous polarization distributions mapping onto high-order Poincaré spheres (HOPSs). The complex laser mode is achieved by superposition of Laguerre-Gaussian modes and manifests exotic flower-like localization on intensity and phase profiles. A simple optical system is used to generate a polarization-variant distribution on the complex laser mode by superposition of orthogonal circular polarizations with opposite topological charges. Numerical analyses of the polarization distribution are consistent with the experimental results. The novel flower HOPS beams can act as a new light source for photonic applications.