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Optical tweezers are designed to trap nano- and micro-scale particles. Once trapped, it is possible to move the particles but this requires complex mechanical adjustments to the optical system. In this paper, an easier way to trap and move multiple particles simultaneously is proposed, that uses a digital mirror-array and freeform micro-lens-array to generate several steerable optical traps inside a light-field.

We developed and fabricated various types of microlenses on optical fiber end facets using a large diameter splicing (LDS) system and analyzed the obtained beam profiles. Numerical simulations support our experimental results.

The gravitational wave detectors have shown a population of massive black holes that do not resemble those observed in the Milky Way 1 – 3 and whose origin is debated 4 – 6 . According to a possible explanation, these black holes may have formed from density fluctuations in the early Universe (primordial black holes) 7 – 9 , and they should comprise several to 100% of dark matter to explain the observed black hole merger rates 10 – 12 . If these black holes existed in the Milky Way dark matter halo, they would cause long-timescale gravitational microlensing events lasting years 13 . The previous experiments were not sufficiently sensitive to such events 14 – 17 . Here we present the results of the search for long-timescale microlensing events among the light curves of nearly 80 million stars located in the Large Magellanic Cloud that were monitored for 20 years by the Optical Gravitational Lensing Experiment survey 18 . We did not find any events with timescales longer than 1 year, whereas all shorter events detected may be explained by known stellar populations. We find that compact objects in the mass range from 1.8 × 10 −4 M ⊙ to 6.3 M ⊙ cannot make up more than 1% of dark matter, and those in the mass range from 1.3 × 10 −5 M ⊙ to 860  M ⊙ cannot make up more than 10% of dark matter. Thus, primordial black holes in this mass range cannot simultaneously explain a substantial fraction of dark matter and gravitational wave events. The results of the search for long-timescale microlensing events among the light curves of nearly 80 million stars located in the Large Magellanic Cloud indicate that there are no massive black holes in the Milky Way halo.

In this paper we simulated the focusing of a second-order cylindrical vector beam by Mikaelian microlens. By using FDTD-method it was shown that the gradient lens produce a region of the energy backflow near its shadow surface. Presence of a microhole in center of the lens allows localize the direct energy inside the lens material and to concentrate the the energy backflow in free space.

Planar digital image sensors facilitate broad applications in a wide range of areas 1 – 5 , and the number of pixels has scaled up rapidly in recent years 2 , 6 . However, the practical performance of imaging systems is fundamentally limited by spatially nonuniform optical aberrations originating from imperfect lenses or environmental disturbances 7 , 8 . Here we propose an integrated scanning light-field imaging sensor, termed a meta-imaging sensor, to achieve high-speed aberration-corrected three-dimensional photography for universal applications without additional hardware modifications. Instead of directly detecting a two-dimensional intensity projection, the meta-imaging sensor captures extra-fine four-dimensional light-field distributions through a vibrating coded microlens array, enabling flexible and precise synthesis of complex-field-modulated images in post-processing. Using the sensor, we achieve high-performance photography up to a gigapixel with a single spherical lens without a data prior, leading to orders-of-magnitude reductions in system capacity and costs for optical imaging. Even in the presence of dynamic atmosphere turbulence, the meta-imaging sensor enables multisite aberration correction across 1,000 arcseconds on an 80-centimetre ground-based telescope without reducing the acquisition speed, paving the way for high-resolution synoptic sky surveys. Moreover, high-density accurate depth maps can be retrieved simultaneously, facilitating diverse applications from autonomous driving to industrial inspections. A meta-imaging sensor detects an extra-fine 4D light field distribution using a vibrating microlens array, enabling high-resolution 3D photography up to a gigapixel with fast aberration correction, demonstrated on a telescope aimed at the Moon.

In an analysis of a large sample of microlensing events, a few suggest the existence of Earth-mass free-floating planets, but only the expected number of Jupiter-mass free-floating objects were detected. No large population of unbound or wide-orbit Jupiter-mass planets Theories of planet formation predict that there should be a population of free-floating planets with masses ranging from less than to several times the mass of Earth. However, the theories do not predict a substantial population of unbound Jupiter-mass planets, the existence of which was surprisingly inferred from the results of a previous analysis of microlensing events. Przemek Mróz et al . have now analysed a much larger sample of microlensing events and place an upper limit, at two standard deviations, on the population of free-floating Jupiter-mass planets that is almost a factor of ten lower than the previous claim, thereby essentially ruling out the existence of this particular population. They do, however, see a few very short events, which, on the basis of the theories of planet formation, indicate the existence of free-floating Earth-mass planets. Planet formation theories predict that some planets may be ejected from their parent systems as result of dynamical interactions and other processes 1 , 2 , 3 . Unbound planets can also be formed through gravitational collapse, in a way similar to that in which stars form 4 . A handful of free-floating planetary-mass objects have been discovered by infrared surveys of young stellar clusters and star-forming regions 5 , 6 as well as wide-field surveys 7 , but these studies are incomplete 8 , 9 , 10 for objects below five Jupiter masses. Gravitational microlensing is the only method capable of exploring the entire population of free-floating planets down to Mars-mass objects, because the microlensing signal does not depend on the brightness of the lensing object. A characteristic timescale of microlensing events depends on the mass of the lens: the less massive the lens, the shorter the microlensing event. A previous analysis 11 of 474 microlensing events found an excess of ten very short events (1–2 days)—more than known stellar populations would suggest—indicating the existence of a large population of unbound or wide-orbit Jupiter-mass planets (reported to be almost twice as common as main-sequence stars). These results, however, do not match predictions of planet-formation theories 3 , 12 and surveys of young clusters 8 , 9 , 10 . Here we analyse a sample of microlensing events six times larger than that of ref. 11 discovered during the years 2010–15. Although our survey has very high sensitivity (detection efficiency) to short-timescale (1–2 days) microlensing events, we found no excess of events with timescales in this range, with a 95 per cent upper limit on the frequency of Jupiter-mass free-floating or wide-orbit planets of 0.25 planets per main-sequence star. We detected a few possible ultrashort-timescale events (with timescales of less than half a day), which may indicate the existence of Earth-mass and super-Earth-mass free-floating planets, as predicted by planet-formation theories 3 , 12 .

Circulating tumor cell (CTC)-based liquid biopsies provide unique opportunities for cancer diagnostics, treatment selection, and response monitoring, but even with advanced microfluidic technologies for rare cell detection the very low number of CTCs in standard 10-mL peripheral blood samples limits their clinical utility. Clinical leukapheresis can concentrate mononuclear cells from almost the entire blood volume, but such large numbers and concentrations of cells are incompatible with current rare cell enrichment technologies. Here, we describe an ultrahigh-throughput microfluidic chip, LPCTC-iChip, that rapidly sorts through an entire leukapheresis product of over 6 billion nucleated cells, increasing CTC isolation capacity by two orders of magnitude (86% recovery with 105 enrichment). Using soft iron-filled channels to act as magnetic microlenses, we intensify the field gradient within sorting channels. Increasing magnetic fields applied to inertially focused streams of cells effectively deplete massive numbers of magnetically labeled leukocytes within microfluidic channels. The negative depletion of antibody-tagged leukocytes enables isolation of potentially viable CTCs without bias for expression of specific tumor epitopes, making this platform applicable to all solid tumors. Thus, the initial enrichment by routine leukapheresis of mononuclear cells from very large blood volumes, followed by rapid flow, high-gradient magnetic sorting of untagged CTCs, provides a technology for noninvasive isolation of cancer cells in sufficient numbers for multiple clinical and experimental applications.

Light-field detection measures both the intensity of light rays and their precise direction in free space. However, current light-field detection techniques either require complex microlens arrays or are limited to the ultraviolet–visible light wavelength ranges 1 – 4 . Here we present a robust, scalable method based on lithographically patterned perovskite nanocrystal arrays that can be used to determine radiation vectors from X-rays to visible light (0.002–550 nm). With these multicolour nanocrystal arrays, light rays from specific directions can be converted into pixelated colour outputs with an angular resolution of 0.0018°. We find that three-dimensional light-field detection and spatial positioning of light sources are possible by modifying nanocrystal arrays with specific orientations. We also demonstrate three-dimensional object imaging and visible light and X-ray phase-contrast imaging by combining pixelated nanocrystal arrays with a colour charge-coupled device. The ability to detect light direction beyond optical wavelengths through colour-contrast encoding could enable new applications, for example, in three-dimensional phase-contrast imaging, robotics, virtual reality, tomographic biological imaging and satellite autonomous navigation. Lithographically patterned perovskite nanocrystal arrays were used to determine radiation vectors from X-rays to visible light and the emission colours of the nanoparticles was used to create images of three-dimensional objects and for phase-contrast imaging.