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Xiaoming Chen, Yanhua Lu, Hao Hu, Lixin Tong, Lei Zhang, Yi Yu, Juntao Wang, Huaijin Ren, Liu Xu
We present investigations into a narrow-linewidth, quasi-continuous-wave pulsed all-solid-state amplified spontaneous emission (ASE) source by use of a novel multiple-pass zigzag slab amplifier. The SE fluorescence emitted from a Nd:YAG slab active medium acts as the seed and is amplified back and forth 8 times through the same slab. Thanks to the angular multiplexing nature of the zigzag slab, high-intensity 1064-nm ASE output can be produced without unwanted self-lasing in this configuration. Experimentally, the output energy, optical conversion efficiency, pulse dynamics, spectral property, and beam quality of the ASE source are studied when the Nd:YAG slab end-pumped by two high-brightness laser diode arrays...
March 5, 2018: Optics Express
Jun Yu, Zhengxiang Shen, Pengfeng Sheng, Xiaoqiang Wang, Charles J Hailey, Zhanshan Wang
The nested grazing incidence telescope can achieve a large collecting area in x-ray astronomy, with a large number of closely packed, thin conical mirrors. Exploiting the surface metrological data, the ray tracing method used to reconstruct the shell surface topography and evaluate the imaging performance is a powerful tool to assist iterative improvement in the fabrication process. However, current two-dimensional (2D) ray tracing codes, especially when utilized with densely sampled surface shape data, may not provide sufficient accuracy of reconstruction and are computationally cumbersome...
March 1, 2018: Applied Optics
Christoph Braig, Ivo Zizak
We investigate the potential of large-scale diffractive-refractive normal-incidence transmission lenses for the development of space-based hard x-ray telescopes with an angular resolution in the range of (10-6 -10-3 )  arcsec over a field of view that is restricted by the available detector size. Coherently stepped achromatic lenses with diameters up to 5 m for compact apertures and 13 m in the case of segmentation provide an access to spectrally resolved imaging within keV-wide bands around the design energy between 10 and 30 keV...
March 10, 2018: Applied Optics
Shu-Cheng Dong, Jian Wang, Qi-Jie Tang, Feng-Xin Jiang, Jin-Ting Chen, Yi-Hao Zhang, Zhi-Yue Wang, Jie Chen, Hong-Fei Zhang, Hai-Jiao Jiang, Qing-Feng Zhu, Peng Jiang, Tuo Ji
Infrared sky background level is an important parameter of infrared astronomy observations from the ground, particularly for a candidate site of an infrared capable observatory since low background level is required for such a site. The Chinese astronomical community is looking for a suitable site for a future 12 m telescope, which is designed for working in both optical and infrared wavelengths. However, none of the proposed sites has been tested for infrared observations. Nevertheless, infrared sky background measurements are also important during the design of infrared observing instruments...
February 2018: Review of Scientific Instruments
Nissim Kanekar, Tapasi Ghosh, Jayaram N Chengalur
We have used the Arecibo Telescope to carry out one of the deepest-ever integrations in radio astronomy, targeting the redshifted conjugate satellite OH 18 cm lines at z≈0.247 towards PKS 1413+135. The satellite OH 1720 and 1612 MHz lines are, respectively, in emission and absorption, with exactly the same line shapes due to population inversion in the OH ground state levels. Since the 1720 and 1612 MHz line rest frequencies have different dependences on the fine structure constant α and the proton-electron mass ratio μ, a comparison between their measured redshifts allows one to probe changes in α and μ with cosmological time...
February 9, 2018: Physical Review Letters
R K Naik, N Leung, S Chakram, Peter Groszkowski, Y Lu, N Earnest, D C McKay, Jens Koch, D I Schuster
In the original version of this Article, the affiliation details for Peter Groszkowski and Jens Koch were incorrectly given as 'Department of Physics, University of Chicago, Chicago, IL, 60637, USA', instead of the correct 'Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA'. This has now been corrected in both the PDF and HTML versions of the Article.
January 9, 2018: Nature Communications
Jose María Ezquiaga, Miguel Zumalacárregui
Multimessenger gravitational-wave (GW) astronomy has commenced with the detection of the binary neutron star merger GW170817 and its associated electromagnetic counterparts. The almost coincident observation of both signals places an exquisite bound on the GW speed |c_{g}/c-1|≤5×10^{-16}. We use this result to probe the nature of dark energy (DE), showing that a large class of scalar-tensor theories and DE models are highly disfavored. As an example we consider the covariant Galileon, a cosmologically viable, well motivated gravity theory which predicts a variable GW speed at low redshift...
December 22, 2017: Physical Review Letters
Luigi Santacroce, Lucrezia Bottalico, Ioannis Alexandros Charitos
Background: In the pre-Hellenistic period, the concept of medicine was not well-defined. Usually, a disease was considered as a divine punishment and its treatment was devolved to the priests who asked for healing from the divinities. The only job that could be compared to medical practice was a kind of itinerant medicine, derived from the Egyptian therapeutic tradition based only on practical experience and performed by people that knew a number of remedies, mostly vegetable, but without any theoretical bases about the possible mechanisms of action...
December 12, 2017: Medicines (Basel, Switzerland)
Lucas R Parent, Evangelos Bakalis, Maria Proetto, Yiwen Li, Chiwoo Park, Francesco Zerbetto, Nathan C Gianneschi
Revolutions in science and engineering frequently result from the development, and wide adoption, of a new, powerful characterization or imaging technique. Beginning with the first glass lenses and telescopes in astronomy, to the development of visual-light microscopy, staining techniques, confocal microscopy, and fluorescence super-resolution microscopy in biology, and most recently aberration-corrected, cryogenic, and ultrafast (4D) electron microscopy, X-ray microscopy, and scanning probe microscopy in nanoscience...
January 16, 2018: Accounts of Chemical Research
Zonghua Zhang, Yuemin Wang, Shujun Huang, Yue Liu, Caixia Chang, Feng Gao, Xiangqian Jiang
The fast development in the fields of integrated circuits, photovoltaics, the automobile industry, advanced manufacturing, and astronomy have led to the importance and necessity of quickly and accurately obtaining three-dimensional (3D) shape data of specular surfaces for quality control and function evaluation. Owing to the advantages of a large dynamic range, non-contact operation, full-field and fast acquisition, high accuracy, and automatic data processing, phase-measuring deflectometry (PMD, also called fringe reflection profilometry) has been widely studied and applied in many fields...
December 7, 2017: Sensors
Joseph A Boales, Farrukh Mateen, Pritiraj Mohanty
Radiation pressure exerted by light on any surface is the pressure generated by the momentum of impinging photons. The associated force - fundamentally, a quantum mechanical aspect of light - is usually too small to be useful, except in large-scale problems in astronomy and astrodynamics. In atomic and molecular optics, radiation pressure can be used to trap or cool atoms and ions. Use of radiation pressure on larger objects such as micromechanical resonators has been so far limited to its coupling to an acoustic mode, sideband cooling, or levitation of microscopic objects...
November 22, 2017: Scientific Reports
Stan Woosley
No abstract text is available yet for this article.
November 8, 2017: Nature
Gretchen Vogel
No abstract text is available yet for this article.
November 3, 2017: Science
(no author information available yet)
On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993...
November 2, 2017: Nature
N Blind, E Le Coarer, P Kern, S Gousset
The next generation of extremely large telescopes (ELT), with diameters up to 39 meters, is planned to begin operation in the next decade and promises new challenges in the development of instruments since the instrument size increases in proportion to the telescope diameter D, and the cost as D(2) or faster. The growing field of astrophotonics (the use of photonic technologies in astronomy) could solve this problem by allowing mass production of fully integrated and robust instruments combining various optical functions, with the potential to reduce the size, complexity and cost of instruments...
October 30, 2017: Optics Express
Tengfei Wu, Jonathan Dong, Xiaopeng Shao, Sylvain Gigan
Recently introduced angular-memory-effect based techniques enable non-invasive imaging of objects hidden behind thin scattering layers. However, both the speckle-correlation and the bispectrum analysis are based on the statistical average of large amounts of speckle grains, which determines that they can hardly access the important information of the point-spread-function (PSF) of a highly scattering imaging system. Here, inspired by notions used in astronomy, we present a phase-diversity speckle imaging scheme, based on recording a sequence of intensity speckle patterns at various imaging planes, and experimentally demonstrate that in addition to being able to retrieve the image of hidden objects, we can also simultaneously estimate the pupil function and the PSF of a highly scattering imaging system without any guide-star nor reference...
October 30, 2017: Optics Express
E E Wollman, V B Verma, A D Beyer, R M Briggs, B Korzh, J P Allmaras, F Marsili, A E Lita, R P Mirin, S W Nam, M D Shaw
For photon-counting applications at ultraviolet wavelengths, there are currently no detectors that combine high efficiency (> 50%), sub-nanosecond timing resolution, and sub-Hz dark count rates. Superconducting nanowire single-photon detectors (SNSPDs) have seen success over the past decade for photon-counting applications in the near-infrared, but little work has been done to optimize SNSPDs for wavelengths below 400 nm. Here, we describe the design, fabrication, and characterization of UV SNSPDs operating at wavelengths between 250 and 370 nm...
October 30, 2017: Optics Express
Victoria Bakare, Grant Lewison
There is a clear tendency for authors of scientific papers to over-cite the papers by their fellow countrymen (and countrywomen) relative to the percentage presence of their papers in world output in the same field. We investigated the Over-Citation Ratio (OCR) as a function of this percentage, and the effects of different scientific fields and publication years. For cancer research, we also compared clinical with basic research. We found that the OCR for a given percentage presence has been decreasing over the period 1980-2010, probably because of better communications...
2017: Scientometrics
Zhichao Dong, Haobo Cheng
The demand for reaction-bonded silicon carbide (RB-SiC) mirrors has escalated recently with the rapid development of space optical remote sensors used in astronomy or Earth observation. However, RB-SiC is difficult to machine due to its high hardness. This study intends to perform ductile mode grinding to RB-SiC, which produces superior surface integrity and fewer subsurface damages, thus minimizing the workload of subsequent lapping and polishing. For this purpose, a modified theoretical model for grain depth of cut of grinding wheels is presented, which correlates various processing parameters and the material characteristics (i...
September 10, 2017: Applied Optics
Iuliia Shatokhina, Ronny Ramlau
In this paper, we present two novel algorithms for wavefront reconstruction from pyramid-type wavefront sensor data. An overview of the current state-of-the-art in the application of pyramid-type wavefront sensors shows that the novel algorithms can be applied in various scientific fields such as astronomy, ophthalmology, and microscopy. Assuming a computationally very challenging setting corresponding to the extreme adaptive optics (XAO) on the European Extremely Large Telescope, we present the results of the performed end-to-end simulations and compare the achieved AO correction quality (in terms of the long-exposure Strehl ratio) to other methods, such as matrix-vector multiplication and preprocessed cumulative reconstructor with domain decomposition...
August 1, 2017: Applied Optics
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